The XS-B20 is a fine copy of the HW-95 also known as the Beeman R9. Most, but not all the parts, are similar. It is a light weight (6.7 lb. - I think mine is slightly lighter than that, but at the moment I don't have an accurate scale in that range) Break-barrel (this references the way you cock the gun) Spring powered Air Rifle. The one that I received (an early production model) has the metal parts polished and blued and a light colored wood stock that (I think) is very nice. The one I have is in .177 Caliber. It is a nice looking gun. I don't have an R9 for direct comparison so you'll have to find that somewhere else. And you will also have to learn how it shoots relative to the R9 from someone else because this (light, powerful, breakbarrel) is not really my kind of air rifle (see below.)
Click here for XS-B20 photo album
The reason that I bought mine is, that in copying the R9, "BAM" (that is what is impressed on the receiver and I'm told that it stands for "Best Airgun Manufacturing" and I assume this refers to the name of the company that made it) also copied the "Rekord" trigger. You'll notice that a lot of this write-up is concerned with the trigger as that was my primary interest. I would say this air rifle is primarily designed for hunters (which I am not - don't care if you are - I'm just not interested.) Hunters like light weight and power - this combination in a spring powered air gun doesn't make for an easy gun to shoot accurately (it is a physics thing, and there is very little you can do to change this.) The airgun itself may be very accurate, but actually hitting something with it requires a very consistent technique and a lot of practice. Target shooters (which I am) prefer low power and lots of weight. So I am not the person who is going to be able to tell you how well this gun shoots (compared to my "target" guns and from a "target" point of view all light weight, high powered spring guns leave something to be desired.) Also when I say, " Hunters may want to do..." I'm guessing. I'll show you how to adjust the trigger...but then I'll adjust my trigger a lot lighter than a non target shooter would (guessing) and I'll mention how to change the mainspring, but you may not want to use the same spring that I do, 'cause I'm going to reduce - not increase- the power. (And I think that a sleeve over the barrel that weighed a couple of pounds and aperture sights would be a good idea - ridiculous! really, given why this gun was designed) In keeping with the "sprit" of this gun I'm not even going to try to scope it, so you won't find that information here either.
I do like my B20 now that I've owned it for a little while. The stock is nice: the pull length (measured from trigger at rest to rear of but pad) is 14 1/4 inches and the forearm width is about 1 7/8 inches which is at least an 1/8 inch wider than the B21 (which I think is a bit narrow.) The pistol grip is a little far back from the trigger for my taste. But overall the rifle has a nice feel. My stock was cut from a nice piece of wood (I know this is luck of the draw) and the red rubber but pad is "OK" but seems to work (it sticks to my shoulder.) The blueing, while it may give something up to the Europeans, is the best that the Chinese have done (to my knowledge.) With a light coat of oil, "it looks good." Except for the looseness in the cocking link (which is also true of my TX200's but not true of my HW97 so it may not be true of a "real R9") everything is tight and works with precision. Really, if you want a gun like this "what is not to like?"
A really useful book to owners of the B20 might be Tom Gaylord's book on the R1: "The Beeman R1 Supermagnum Air Rifle" as there are a great deal of similarities between these two rifles. And the instructions here can make up for a lot of the differences which are mostly in he way the rifles are put together. Compared to your B20 the earlier R1 (1981) was heavier, (8.6 lb.. vs. 6.7 lb..) longer, (45.2 in vs. 42.3 in) and about the same advertised power (900-940 vs. 900-950 with nobody specifying which pellet they are using.) Tom goes into a lot of detail about how to shoot the R1 and tests a lot of "good ideas" that you might have thought of to "improve" your B20 to save you a lot of time and trouble.
Another book if you are interested in the technical aspects of how airguns work is "The Airgun From Trigger to Target" by G.V. Cardew and G. M. Cardew. It probably doesn't exactly work the way you would initially guess.
It appears at the current time (pretty early in the program) that these rifles can be "tuned" using parts designed for an R9 or some other model, "maybe." Russ has reported that, "The compression chamber diameter is .982". An R-9 chamber runs about 1.023" (give or take)." And when I tried a "universal" spring that is suppose to fit in the R9 it did not fit as it was just slightly too big. A lot of air rifles were designed arround the 25 mm bore and HW went to the 26 mm bore on their rifles in the 1990's so that they wouldn't have to carry so many parts. Other than the spring I haven't done any parts replacement yet. But I do know that Russ Best (Bestunes) was working on tuneing one and he does good work. My previous experience with springs made by Jim Maccari would lead me to believe that if he makes a spring for a gun it is really a good spring (ask if it fits the B20. And the rifles (R9, B20) look so close to me that custom stocks for the R9 ought to fit (but ask the stockmaker.) So it looks like there will be lots of "aftermarket" equipment available for a person to "improve" their B20. And so on to the little information that I can provide.
Though I tested everything that I am telling you here (unless I say I didn't) they were tested on my only B20 which is Serial No 16 obviously an early production model. Any thing can be changed and probably will with time and each air rifle is a little different. It worked for me, but I am used to doing mechanical things. If you are uncomfortable doing this kind of work, Don't. There is a big spring in there and it can hurt you! Be careful! Make sure you fully understand what you are about to do Before you do it. This is the Internet I could have made a mistake or typo, or someone could have changed what I really said. Think it through and if you are not completely sure what you are doing - keep reading and questioning. I'm just providing information to help out the hobby and so someone will provide me information when I need it - I'm not getting paid. And I'm not responsible for what you do.
What do you do when you first receive your rifle.
You mean, after you remove it from the Styrofoam box and the plastic wrapper and finish the ohhs and ahhs about the nice wood stock and nicely made parts? Then you wonder why your bluing doesn't look shiny like the pictures. Well it is covered with a sprayed on preservative. What you need to do is wipe this preservative off with your own preservative (Something that will keep the metal from rusting where you handle the gun. Because this is a break-barrel you have to touch the barrel each time you cock the gun and the salts from your hand and the moisture from the air is going to try to rust that barrel so you need to wipe it down with some oil or silicone that will prevent this. Some other considerations about whatever you choose: It shouldn't be too slippery as you have to hold on to this barrel when you cock the gun. And it shouldn't hurt the finish of your stock, 'cause after you take your hand off the barrel you are going to grab the stock*. ) Then it will be shiny just like the pictures.
*I use Hideout Premium Gun Oil (No smell) by Hughes Products. This works great, but I haven't got a clue where to get any more.
Well, basically you check it. Then you shoot it.
Click here for XS-B20 photo album
First I'd read the instructions, "The little blue book." They are not bad for a Chinese airgun (or any airgun really.) There is a lot of basic and useful information (I wish they would have included a parts diagram, but...) I disagree with the comment to: place two drops of chamber oil in the chamber every 1000 shots (I think that you place oil on the spring and let it work its way to the chamber or you place grease behind the piston seal and let that lubricate the chamber - but more on that later and you've got a while to study the pros and cons before you get to the 1000 shot mark.) But that is all that I disagree with except the loading picture!
>WARNING< To be safe you should restrain the barrel of your airgun when you put your fingers in the breech area! And while doing this you shouldn't have your other hand anywhere near the trigger "just in case." (Unlike the picture in the manual.) The contortions to accomplish this are up to you - I am able to hold the barrel with my left hand with the but resting on my upper leg and use my right hand to put the pellet in.
So now I've read the instructions, what then? Lets just check the rifle out.
Look it over for loose or missing screws. There are 4 that are important at the moment: two in the trigger guard (big in front and little in back) and two, one on either side of the "forearm." These should be "there" and snug. A word about stock screws. If you put your new No 2 Philips screwdriver* on any of these stock screws and tighten as hard as you can they will turn. All have a layer of wood between the screw and metal. Wood can be compressed (to the point where it cracks.) "Snug" is the operative word here. And check them every so often.
Now check the barrel for obstructions: Start to cock the rifle. It is going to be stiff at first (you'll probably be surprised at how hard the initial break is) - don't bend the barrel - but start the cocking stroke. Then you'll be able to see down the bore (from the place where you put the pellet = the breach.) I like to run a cleaning patch through the bore, but as it says in the instructions, "airgun rifling can be damaged by improper cleaning" - so if you don't know what you are doing just check it for obstructions (you can read up on proper airgun cleaning elsewhere.)
Now finish the cocking stroke. The piston should lock up (the spring should stop pushing back) and The SAFETY SHOULD POP OUT. This is real important as it checks most of the functioning of the Record trigger and is your only "anti beartrap" safety (a "beartrap" is if the spring is released while the barrel is open and your fingers are placing a pellet in the breach - this is a bad thing!) If it doesn't pop out try cocking it a couple of times - again you don't want to bend the barrel, but it just might be a little more effort or a couple of tries will get it to pop if it is stiff and new. If the rifle cocks but the safety doesn't pop be VERY careful when you load and fire the rifle. You should restrain the barrel when you load anyway.
Put the pellet in (try never to fire this gun without a pellet .) Close the barrel check the 'lockup' (should be in the same straight line with the 'receiver as it was when you got the gun and tight.) And fire the gun (push safety off. pull trigger) while it is pointed at something safe (don't expect the sights to be "zeroed" when you receive a new gun - so have some room to miss.)
Then What? Shoot it! Airguns all take some time to break in and for quite a while it will get better and smoother with each shot. At least 100+ shots will be required before any real accuracy can be tested and before I would adjust anything. Plus you can start to get used to it and perfect your shooting technique (you can read about that somewhere else.)
*Regular screwdrivers will work on this gun, but it was obviously made by a gun manufacturer that used gun type screws so that the special screwdirvers that gunsmiths use fit just perfectly and provide much less chance of damaging the screws.
Now about that Record Trigger?
OK, I'm shooting this rifle and the trigger is starting to smooth out, but it is "OK," "Good," "Like an old military trigger with some creep in the second stage," Nothing to write home about. What is all this hoopla over the famous "Rekord" trigger anyway?
Well the trigger on your B20 is a pretty good copy of the German "Rekord" trigger (that is why the funny spelling.) It is not a perfect copy (there are differences) and it is a "little crude around the edges," but the mechanism is there and it can be made into a pretty fine (and still safe) trigger. Most of the work is just adjustment. The operative phrase from the instructions is: "Before it left the factory the trigger was adjusted for full weight and sear engagement to ensure safe and correct operation." There are two adjustments on this trigger and the factory has set both to "max safety." (well almost.)
If you had paid the extra money for a real Beeman R9 some technician in Germany would have been paid to adjust your trigger to a fine edge. And you wouldn't be asking, "what is so special about a Rekord trigger." Here is what you would be told about trigger adjustment (copied from my Beeman HW97 Owners Manual:)
"Trigger Adjustment: The trigger is two stage. The first stage, considered by European shooters as a safety feature, consists of a fairly long slack phase - sometimes mistakenly identified by American shooters as "creep." The second stage is the actual trigger pull. The basic adjustment is made by the factory using screw 52b (Fig A.) DO NOT ADJUST THIS SCREW! It must be adjusted only by the factory or factory-authorized service station. Improper adjustment may cause the gun to fire when snapped shut. Fine adjustments can be made simply by inserting a screwdriver through the hole in the trigger guard and turning screw 51a behind the trigger. Counter-clockwise turns produce a lighter pull. Adjustments below about 14oz pull are not recommended. Clockwise turns produce a heavier pull. Excessive lubrication and all molybdenum disulfide lubricants should be kept off the trigger sears. Note: Please use care when replacing the trigger guard: overtightening the rear trigger guard screw may make it impossible to release the trigger."
Well, almost all of this is good advice for a B20 owner except if we want to see what a "Rekord" is suppose to be like we are going to have to "touch the untouchable." But before I show you a suggested way to do that safely some other comments. (By the way if your B20 trigger is "good enough" for you the way it came - leave it alone. For most hunting situations this will probably be true.)
The B20 trigger is a real two stage trigger (unlike some other air guns - Qb88, B18, Gamo, etc.) This means that the first, easy, stage really is moving the sear. If you are going to adjust this trigger to a fine edge YOU NEED THAT FIRST STAGE TO BE SAFE. Adjust this trigger to an easy single stage and it is Dangerous! (Are you listening! - I figure if you are smart enough to read and understand these instructions you are smart enough not to do foolish things with an airgun - Don't prove me wrong!) Don't start doing any adjustments till you have read through this whole procedure.
Once the trigger is adjusted here is how it is suppose to work: You get your gun sighted in generally on the target press off the safety and you "take up the slack." That is an old military term for pulling through the first stage until you feel the increased pressure of the second stage. You hold here till the time for trigger release and just a slight bit of increased pressure (set to taste) causes the gun to fire.
The best way (and safest) to adjust and to see how the B20 trigger works is out of the gun. This trigger can be cocked and "fired" outside of the gun. This is the "best way" because of two warnings: Don't fire the B20 without a pellet. And Don't fire the B20 without the trigger guard securely in place (once you've figured all this out and have the adjustments pretty close you can just remove the trigger guard, make a fine adjustment, put the guard back, load and fire - but let's do it this way the first time.)
Click here for XS-B20 photo album
So Lets take the trigger out of the Gun.
This is a relatively easy thing to do (especially getting it out, back in is a little trickier.) No special tools other than a 1/8 punch and No spring compressor is required for this step. But the Standard Caveats apply. Read through the whole procedure and if you aren't comfortable doing this kind of work, Don't.
First step is remove the stock.
Those same four screws (two on the forearm and two in the trigger guard) that you checked when you got the gun are the "stock screws" take them all out (a good No 2 Phillips head gunsmith screwdriver -CRV PH2- worked for me.) Now since the two screws in the trigger guard are out, remove the trigger guard and put it aside with all the screws. Now the gun should slide out of the stock.
I would do all this work over an old sheet (or something of light color)
down on the floor as things can fall out. In this case the rear trigger
guard screw fits into a nut in the back of the Trigger Assembly. This nut
is loose (it was on mine at any rate,) but held in place by the stock.
When you slide the action out of the stock this can fall out. If it doesn't,
see if yours is loose, and if it is, get it out and put it aside along
with the stock so it won't be lost or damaged.
The Trigger Assembly is held in by the two small pins (about 1/8" in diameter) that you see on either side of the receiver where the trigger assembly is. You need to tap these out. I use a small punch (looks like 1/8" though it isn't marked) for this and it will be useful when you put the trigger back to help you get things aligned. On my B20 it looks like the pins are not tapered and they can be tapped out to either side (not true of the HW97) but if you tap in one direction and they don't go try the other direction. It should not take too much force to get these pins out - I just hit the punch with the plastic handle of my screwdriver. Drive the back one out first. Then rotate the trigger assembly about the front pin by pulling up on the back end and expect the safety pin and spring to pop out (maybe not, as it is a pretty light spring and you may grip it with your fingers and give it a gentle pull (if it doesn't come out don't worry, but don't loose it if it does decide to pop out.) Then tap out the front pin. Now you can lift out the trigger assembly - be careful as one of the tubes in my trigger assembly was loose and wanted to fall out, keep it all together as it has to all be there to work. Tah, Dah, that is all there is too it! Put the safety and the two pins (the pins are different lengths the front one is the longer one) aside so they won't get lost or damaged. Also put the rest of the rifle with them as we are just going to work with the trigger assembly for awhile.
>WARNING< You know that big pin that looks like it goes through the trigger assembly. IT IS NOT A PIN! IT ISN'T INVOLVED IN THIS STEP! LEAVE IT (actually them) ALONE!
I am going to tell you how this trigger works (theory) and how to make the adjustment (pretty simple = two screws) in the next sections. But at this point - with it in your hand - you can figure out how to cock and "fire" the trigger. To cock: push the rear of the top lever (the one that hooks the piston on the other end) down into the trigger until it catches. You'll need something to push with - I can do it with the punch or a screwdriver. Be careful and try not to scratch the parts too badly. Once it locks in place pull the trigger and "fire" it. This will release the top lever. You need to know how to do this for the next sections and to get the trigger assembly back in the action.
Getting the trigger assembly back in the action as they say is "just the reverse" of getting it out, but it will go a lot easier if you cock the trigger before you start to put it back. So that it the first step. The last step, once it is back. is to "fire" it. If you don't do this the rifle will refuse to cock - The piston is hitting the front of the hook of the top lever and can't get by that.
So you cock
Slip the front of the trigger assembly in.
Tilt down and tap in the front pin.
Slip in the safety and hold it in while you lower the rear of the trigger assembly into place and tap in the rear pin.
Fire the trigger. (And Bob's your Uncle!)
It is a little fiddly moving things around till the pins line up and tap in easily - if it isn't working too well try the other end of the pin (the pin should have the sharp end rounded off a little) or come in from the other side. And I have found the punch useful to get things lined up. But it really isn't to difficult.
You should be careful with all the parts of this trigger (actually the
whole gun) it is a good quality steel, but I received this note from Russ
Best (Famous Airguning Personality - FAP:)
"if a trigger assy wobbles after it's installed into the gun (both pins in place)the gun may fail to cock. The safety button might pop out to the SAFE position, but the sear never latched. If that happened, push in the safety button and try to re-cock the gun. It may work correctly on the second attempt, but this is a sign of a sloppy trigger unit. These units need to be solidly held in place. I've seen a couple real Rekords develop a problem if the wrong punch is used and the pin holes wind up getting stretched oversize. This often occurs with DIY'ers, and the only 'neat' fix is a brand new main tube. Regards, Russ(Bestunes)"
If this is all you were going to do - Put the nut back in the trigger assembly. Slide the stock on. And replace the four screws (Snugly, remember) Then cock the gun (if it doesn't cock - did you fire the trigger? - did you adjust the spring tension too loose?) Put a pellet in and go try it.
This section is theory because you can't really take your B20 trigger assembly apart and change anything (at least I'm not willing to) this is also true of the Rekord. I think that the Rekord trigger is put together by drilling the holes where the pins and tubes fit into the side plates just a little undersized. Then when the trigger is assembled the side plates are pressed on. "BAM" in the B20 decided to make the pins long and then smash (rivet) the ends to hold the assembly together. Both methods work, but neither makes for a trigger assembly that is easy to take apart or reassemble (there are people who do this kind of work on the Rekord and who may in the future work on the B20 - so it is not impossible.) It would be nice to take this trigger apart and polish the rubbing surfaces, but for now I'm going to rely on "working" the parts in by shooting the gun. But here is how it works:
and the B20 triggers are four lever triggers. When the Reckord was designed,
back in the 50's (yes the 1950's though triggers go back a long way) it
was considered a match trigger. Usually with a trigger the number of levers
increase with "goodness." In order to talk about the parts I am going to
have to label them: so here is a drawing with my names labeled on it:
I decided to start numbering at the point where the most force is, because the purpose of the first two levers and angles (at the sears) is to reduce force. That is what levers do, but I'm getting ahead of myself.
In order to understand triggers you need to understand two ancient machines: The incline plane and the lever.
So here is George the Egyptian trying to get a big stone block a couple hundred feet up the side of the Pyramid. He uses an incline plane. The block (on rollers to reduce friction) is moved 1 foot (cubit? whatever) up for every 20 feet along. If the block weighed 1,000 lbs it would be pushing straight down with a force of 1,000 lbs, but it would only be pushing towards George (down the plane) with a force of about 50 lbs (if there were no friction) This is what happens at the "Piston Hook" on lever No 1. The piston is trying to pull forward with a force of about 400 lbs (depends on your mainspring and I'm guessing.) There is a shallow angle where the piston and lever 1 are hooked together this causes a force down on that end of lever 1 that is much less than 400 lbs - say 9 lbs. (Us engineering types should also notice that the 400 lbs of force is transferred to the frame by the pivot of lever 1 which is the forward tube, which has the front pin through it - i.e. it is the front pin that carries the load - good design.)
A lever is a solid piece with a pivot in the middle (or not in the middle.) When you press down on one end the other end rises. So I've got this solid steel rod 4 inches long. If the pivot is in the middle (at 2 inches from the end) 9 lbs pushing down on one end will push up with 9 lbs of force at the other. But if you move the pivot so that it is 1 inch from the 9 lbs pushing down, then at the other end which is 3 inches from the pivot the upward force would be only 3 lbs. The reduction depends on the ratio of the two distances to the pivot. OK. look at lever 1. The measurements are: Hook to pivot pin = 1/2 inch (these are just "eyeball and ruler" measurements) Pivot pin to other tip of lever 1 = 1 5/16 inches. So we would change the 9 lbs down to 2.75 lbs. (Formula: the torques about the pivot have to be equal 9 X .5 = 2.75 X 1.625.) So you can see the force, which is really the force necessary to control the release of that 400 lb. mainspring is being reduced with each step. Lever 2 works exactly the same way reducing the force at the sear 2 but since the pivot point is near the middle (about 1/2 inch each way) as a lever it really just changes the direction of the force. By the time the force reaches sear 3 it is very small.
Remember George with his block on the inclined plane? What if the block and the plane were made of polished steel and there were no rollers (be one heck of a pyramid! but this is just a "mind experiment.") So now George and his three friends can push the block up the plane and when they want to rest one of them can hold it there (while the other three go get coffee.) One day their supervisor decides to help them out and spreads Molybdenum Disulfide (Molly) on the inclined plane. Well, besides being very black (on George's feet) Molly forms a coating (actually bonds to the metal) on a steel surface that is very low friction when rubbed against another coated steel surface (doesn't work at all, or as well, on other materials.) It is easier to push the block up the plane, but when George's friends want to go for coffee they can't leave George alone to hold the block. Some triggers are designed such that some friction is necessary to keep them safe - this is mostly true of American two lever single stage triggers. So now you can see the reason for the warning against Molly on any trigger. Before getting it near the working parts of a trigger you have to know that the friction reduction won't cause a problem. My analysis of the Rekord and how it works leads me to believe that Molly will not cause it to become unsafe and I'm going to recommend that it be used in one specific place to reduce the friction to its lowest point - not to make the trigger pull lighter, but more consistent as friction can vary a little with each pull.
The first two levers have reduced the level of force to be controlled to a very low level probably on the order of ounces by the time it reaches sear No. 3 (actually, the spring of lever 2 is probably providing almost an equal force at the sear)
Now that we got that out of the way what do the other two levers do? all mechanical triggers are effectively pulling one piece of material (usually metal today) out of the way of another to release a spring. This is usually called a "sear" and as you can see on the drawing I labeled 3 sears. There is only one that you "feel" and that sets the timing of this trigger: Sear No. 3. The other two sears are tripped automatically when sear no 3 is released. In the Rekord since the amount of friction provided to lever 3 from lever 2 is relatively small almost all of your trigger feel comes from the adjustable spring and the mechanical leverage between the trigger (lever 4 ) and lever 3. This is what these two levers do; and this is why you can set this trigger pretty well with it out of the gun (this is not usually true of other than "match triggers" -- but then this started life as a "match trigger.")
How do they do that? Well the force we are interested in now is the force that you feel in the trigger (lever 4) as it presses on and moves lever 3. The first obvious thing is that the force that moving the trigger has to overcome is: the friction on the sear (No 3) (which we already know is very small;) the friction of its moving parts (also small;) AND the force that is applied by the spring that is compressed by the Tension Screw. So we set the overall trigger pull force by adjusting the Tension Screw (old "51a") The reason for not setting it below 14 ounces? There is some friction in the movement of the trigger, lever 3, and sear 3. You need enough spring push to make sure that if you pull the trigger up to the second stage (setting the sear on a knife edge) and then relax it, the sear resets to its safe position. The 14 ounce figure is probably a very safe one on a well lubricated trigger and with the trigger out of the gun you can watch this movement happen.
The trigger lever has two bumps on the surface where it contacts lever 3 and each is a different distance from the pivots of both the trigger and lever 3. When you switch from touching on the forward bump which is a short distance from the trigger pivot but a longer distance from the pivot of lever 3 to the rear bump the force required by the trigger to move lever 3 against the spring changes. The force increases. Also the leverage changes - with the light force you move the trigger a lot and lever 3 moves a little. With the heavier force you move the trigger a little and lever 3 moves much more. What you want is for that force increase to happen just before the sear 3 is about to release. If the trigger could be manufactured to "perfect" tolerances and wouldn't wear, they would simply make it that way and there would be no need for what I labeled the "Sear Engagement screw and the extra part of lever 3. But that "double lever and screw" is the way the designers of the Rekord trigger chose to take out all the mechanical slop that occurs in the manufacture of a real trigger. (Air Arms in their TX-200 copy of the Rekord chose to replace the little bumps on the trigger with screws that are threaded through the trigger and make their adjustment there so their lever 3 is a single piece - probably a better method, but now you have two screws to adjust instead of just one.)
Why are the levers the funny shapes that they are? And what about those other two springs? Well that is so you can cock the trigger by pushing the piston pin into it. Lever spring 1 positions lever 1 down and out of the way of the piston pin and lever spring 2 positions lever 2 out of the way of the end of lever 1. When the piston runs into the face of lever 1 (which is above the pivot of lever 1) it forces lever 1 to rotate. The end of lever 1 rides on the face of lever 2 causing the top to rotate forward. When the bottom end of lever 2 slides off the end of lever 3 the sear sets and the whole thing is "locked and cocked." This motion of lever 2 also lets the safety pop out to the safe position which will block lever 2 until it is pushed in.
Well enough theory and watching, lets do something!
Actually Making the Adjustments.
Special tools required for this step: A screwdriver (Allen wrench) to fit the two adjustment screws on the trigger. I used a Gunsmithing screwdriver set (you do have one of those don't you?) And the bit was marked "CR-V6-3/16 ( "beats me" but the blade is probably 3/16" wide.)
Ok, you've got the trigger assembly out in your hand and you know how to cock and 'fire' it. You'll notice that there are two screws, on my B20 they are slotted head screws. One in the front of the trigger and one in the back. The one in the back adjusts the tension on lever No 3 and since the trigger bears against lever No3 it adjusts most of the force that the trigger has to overcome (the rest of the force is provided by friction from the sear and it is relatively small.) Since we are going to change the feel of the trigger a lot with our other adjustments and since this screw can be adjusted anytime you want to, through the hole in the trigger guard, leave it alone for now. But I will caution you to not adjust it too light or if you have already done so put some tension back on this screw because we want lever No3 to seat properly for adjusting the forward screw.
OK, here we violate the rules (Beeman's.) As you cock and fire the trigger assembly you can see the sear (No3) work through the hole in the rear lower quarter of the trigger assembly. What should happen is when you take up the "slack" (to the point where the tension increases) the lever No3 should move and when you release the "slack" it should move back to where it started. This is good. This is your first stage safety. This little bit of sear engagement enables you to set the trigger to as fine a knife edge as you want (on the second stage) and still have a safe trigger. But first, "fire" the trigger and with a toothpick put a small dot of molybdenum disulfide lubricant (a black grease sometimes called Gunslick - or if you don't have any - some regular gun grease) right there on the sear part of lever No 3 where those two levers overlapped. (oh horrors!) Tom Gaylord (another Famous Airgunning Personality) in his book "the R1" recommended this and I agree. Those two levers are at right angles and so you are not increasing any pressures. This and the 200 to 300 shots that you have fired by now (you did didn't you?) should smooth out the sear motion to eliminate any effects of friction or grit on your trigger pull. Then cock and "fire" the trigger a couple of more times to work it in.
"In for a penny in for a pound. " Now start adjusting the forward screw and what you'll be doing is turning it in (clockwise looking down on it) to reduce the amount of sear travel of the second stage to where you want it. Well that's the theory anyway. When I got my B20 this front screw was screwed down on two lock washers and there was no way to turn it in. The reason for this is that without the lockwashers the screw was a fairly loose fit in the threads and probably would have backed out of its hole over time and fallen out. This is perfectly safe as this would have given you the longest heaviest second stage possible, but not what we are trying for here. In an actual Rekord trigger this front screw (the "no touch screw") is a Torx and is quite difficult to turn. It will hold its adjustment. By the way, near the limit (when the second stage is about to go away,) if you want to go there, you will be making adjustments of as little as 1/16 of a turn. If your B20 just has a screw and it fits tight, just turn it in to get the trigger that you want. If it is like mine you'll have to do something to make this adjustment possible. My first move was to remove one of the lockwashers and see how the trigger was tightened down on just one. "Not too bad" and some of you may want to quit there. I then thought about using some sort of "locktight" (the blue - not the one where you can never get it apart) to hold the screw in place since it would take a while to "lock" and I could get the adjustment done then let it "lock." You may have another solution. But what I did was go to my hardware store and buy a metric "grub screw" ("set screw" a screw with no head - that you tighten with an Allen wrench) 4mm in diameter and 8 mm long (at least I think that is what those numbers were telling me though it looks a lot longer than 2 times its width - I took the old screw along just to be sure) and a 4mm nut to fit it. I screw this screw in to set the sear engagement and screwed the nut down on it to lock it. That worked for me. Looks serious too.
Adjust. Cock. "Fire." Get the trigger to where you want it while it is out of the gun. Then put it back and go test it. Now that you know what you are doing you can make the final fine adjustments with the trigger in the gun. In my case (because of the lock nut) I still have to take the stock off, but some of you may only have to take out the trigger guard. Don't fire the gun with the trigger guard off. And Don't adjust the gun so that you don't have any second stage (it can be very light, but it has to be there to be safe.)
A consideration as to how heavy you want your second stage and tension to be: If you are a hunter and you are going to shoot after a lot of exertion, or when it is cold, or when you are excited; you definitely will not be able to feel as fine a second stage as you will at the target range (I.e. don't set it too fine or it will go off when you don't mean it to.)
Don't worry, as now that you know how, as your taste changes or the parts wear you can go back in and "fine tune" your adjustments.
Replacing the Mainspring
Why would you want to replace the mainspring? Well that is up to you. The do break sometimes. Or you might want to try a different one (that is why I did it.) At any rate, since you are almost there, when you have the trigger out, I might as well tell you how to do it.
Click here for XS-B20 photo album
First, Special tools: You are going to need a Mainspring Compressor* especially if you have the original mainspring in there, 'cause it has a lot of preload (that means the spring is pressing very hard on the "End Cap" of the rifle even when it is not cocked.) The Mainspring Compressor made from a cut 8 inch "C" clamp would probably be ideal because your Mainspring Compressor has to allow for a little bit of rotation. You will also need a flat bladed screwdriver (I used a 1/8") and a small Allen wrench or a bent piece of stiff wire (and maybe a 1/16" punch.)
Here is how
Remove the Stock.
Remove the trigger assembly.
Put what is left of your rifle in your Mainspring Compressor and begin taking up the tension on the End Cap. Make sure that you are only pushing on the End Cap. Now remember that I said the original mainspring (if it isn't broken) is putting quite a bit of tension (pushing out) on the End Cap. Well your Mainspring Compressor has to put an equal amount of tension the other way (pushing in.) As you increase the tension get your small Allen wrench (or bent piece of stiff wire and try to push the "Buttons" out through the hole in the inside of the End Cap (the hole that the trigger assembly came out of.) Watch the end of the End Cap where you are pushing. It will flex a little, but you don't want to push so hard that you bend it permanently. This is actually a pretty tricky operation. You need to get the balance right while you have pressure on the back of the "Button." Try both "Buttons" and increase and decrease the tension. When you get it right the "Button" will POP out - so you probably should have a rag or something in the way to catch it. When one Pops out you have the tension just right and you have a hole to work through so you can use a small punch straight across to pop out the other one. In this case it is the "getting it apart" that is the hard part. Putting these back was easy. We are not done yet. Don't release the tension on your Mainspring Compressor.
Do you see in the back of the trigger assembly slot on the right side a little "tab" on the End Cap that is in a "slot" in the Receiver? Put your screwdriver behind the tab and rotate the End Cap so that the tab is out of the slot. Now you can release the tension on the Mainspring Compressor and the End Cap, The Spring Guide and the Mainspring will all slide out.
To put back "just reverse the process." Just one caution here. You noticed that the Spring Guide is hollow. Well as you are putting it back in it has to slide over the piston pin. watch through the cocking slot (a good strong light or a flash light helps here) and make sure that happens before you put too much pressure on the whole assembly and crush the end of the Spring Guide. When your Mainspring Compressor has the End Cap in the right position rotate the tab into the slot, press and tap the Buttons into place and you did it! With those Buttons it is a lot easier to put back than to take apart.
*There are plans for Mainspring Compressors on the Internet. There are none for sale that I'm aware of, but I understand the Bsquare may have one in the near future. They are a simple device that allows you to put a controlled amount of tension on the End Cap of an airgun. As I mentioned, there is one that is a couple of pieces of wood and an 8 inch "C" clamp. The "C" clamp has the bottom part of the clamp cut off (the top part has the screw in it) and two holes drilled in it. The clamp is mounted on a block to a board with two screws thought the holes. There is a block screwed to the board at the other end to provide support for the muzzle (that is where all the pressure ends up.) I think for the B20 you almost have to have one to get those little "Buttons" out.
The rest (almost) of the Rifle:
Well, I was going to wait to disassemble the rest of the rifle until I had a pair of Gunsmithing screwdrivers to loosen the bolt that holds the barrel in the jaws of the action. I know it looks like two screws, but the "screw" on the right hand side is a nut. In trying things to measure the gap I tried a nickel (a nickel, by the way is about .065 inches thick and I think the gap is about .070 inches - so that is the screwdriver that I was going to order.) When I turned the nickel with my fingers just to test it, the nut turned. Viola, I can take this thing apart now and not have to wait. The other special tools that you will need are a couple of small screwdrivers and a couple of small metal files. So then:
Off with the
Off with the Trigger.
Out with the mainspring (Oh yes, this time I noticed that the End Cap is pretty light. ah, it is made of aluminum painted black - interesting - nicely done - I don't know what the R9 End Cap is made out of.)
Now you have to take the barrel assembly out of the jaws. First I unlatched the barrel (this was actually the hardest part - that is a strong latch and without the stock it is hard to unlatch. And I'm not too sure this is necessary you might try it without unlatching - I will next time.) Unscrew the "nut" on the right hand side. Take it off and take out the spring washer that is behind it. Now unscrew the bolt from the left side - that's right, the nut is just a locknut. The bolt threads into the right jaw. And remove the bolt.
Now the barrel assembly and the cocking link can be drawn forward. Draw it all the way forward and the cocking shoe will line up with a hole that is just the right size to get it out. The cocking link will unhook from the cocking shoe and you can put the barrel assembly aside. Note here: that on either side of the barrel assembly where the pin went through, there is a "shim" (a thin piece of metal like a very thin washer ) don't loose these. Also note: that each one has a "pushed out" rim on the inside. This rim will fit into the barrel assembly and keep the shim in place when you reinsert the barrel assembly between the jaws.
Now you have to work the cocking shoe out through its perfectly fitting hole. I was able to do this with a little patience and a couple of small screwdrivers. Now by pushing gently with a screwdriver on its various parts you can slide the piston out of what is left of the rifle.
You will probably find the piston seal (the plastic part on the front) slightly cut at various places on the rim. This is why: that slot and those holes that the various parts went through on the bottom of the rifle are all punched out from the outside. If you feel on the inside (be careful) you will find a sharp (very sharp!) edge. That is what cut your piston seal when it was put in and when you took it out. I have found this on every break-barrel I've ever taken apart (B18, Gamo 880) and Tom Gaylord mentions it in his book on the R1 so this isn't the first (or last) air rifle to have this problem (another reason I'm not fond of break barrels.) Depending on how badly cut your seal is you may choose to replace it - they are actually pretty rugged and if it looks like it will still make a good air seal when it is under pressure you may choose not to replace it at this time (I put mine back.) But you do want to take a couple of small metal files and smooth out this sharp edge arround all those holes and slots, so that you don't cut your new/old seal and your fingers when you put the rifle back together.
That is as far as I went with the disassembly. I didn't even try to get the latching pistons apart.
Now with the rifle in this state of disassembly you can properly lubricate the internal parts (If you choose - except for the spring which I had oiled through the cocking slot anyway - I found some form of oil or grease in all the places that it should be.) I chose to wipe off all the old lubricant on the piston and put some "molly" grease on the spring and the outside rear of the piston. I put a thin layer of clear tar (it is a light grease like petroleum jelly) on the back half of the piston seal and on the piston right behind the seal (to act as fuel - see the Cardew's book.) I left the lubricant on the barrel assembly that was there. But generally cleaned and greased with "molly" any rubbing surface that I could figure out. Don't get any grease/oil ahead of the piston as that will be in the compression chamber and will cause dieseling.
So then all you have to do it put it back together. It all went back pretty straight forwardly. Piston in and all the way forward. Align the hole and the hole in the piston for the cocking shoe and place the cocking shoe in (it will go easier now that you have filed off the sharp edges.) Hook the cocking link into the shoe and slide the barrel assembly between the jaws (shouldn't be a problem, but make sure that the shims are in place right side in.) Thread in the bolt and tighten finger tight. Thread on the lock nut on top of the spring washer.
Now tighten the bolt till the barrel will just drop of its own weight when it is not latched (that is where you want to end up I went a little bit beyond that - so it just wouldn't drop - as I'm expecting a little more wearing in.) Then lock in place with the lock nut. It didn't take much tightening - but the barrel drop after the gun is cocked will let you know if this bolt is coming loose so it isn't anything to worry about.
Put everything else back according to the previous instructions and you should have a pretty darned nice air rifle that you know how to care for and maintain.
It is a nice gun. Mine was well made. I was impressed with the quality of the parts and how well the important parts fit together. Now that I've had it apart and reduced the power of the mainspring*, cleaned and lubricated everything (not really necessary, but it helps) adjusted my trigger to a fine edge, and practiced so that I have regained some of my technique for shooting spring powered air guns, I think I'll keep this one.
*If anyone wants to know - the spring came from a collection of "take outs" and production springs that I bought from Jim Maccari a long time ago when he was cleaning out his shop. It looks like a "take out" (doesn't have the frosted silver look that JM springs have) and is about 9 inches long with an Outside Diameter of .783 inches and a wire diameter of .143 (I forgot to count coils.) I don't know what it came from. The Inside Diameter of the Sleeve that is in the piston is about .821 inches and remember that springs grow a little when they are compressed. This spring is compressed by 9/16" of an inch to get it in the gun - which is not much precompression so there is not much force on the end cap and I can assemble the gun with my fingers when this spring is installed. With the "tune" (actually just a "clean and lube") the rifle is now shooting CPL's (Crosman Premier Light = 7.9 grain) at 775 ft/sec very consistently and is easy to cock (the hardest part is just getting the latch open.)
tip on how to modify Gamo trigger of B18 into a Rekord styled true 2-stage