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Education / Training BSF S20 air pistol: Part 1

BSF S20 air pistol: Part 1

by Tom Gaylord
Writing as B.B. Pelletier

The BSF S20 pistol looks like a breakbarrel rifle that’s been cut down to fit into a pistol grip.

A history of airguns

This report covers:

  • BSF S20
  • Finding the gun
  • Some faults
  • Not so simple
  • Description
  • What to do next?


I saw my first BSF S20 pistol in an antique shop in Fürth, Germany in the mid-1970s. I went there to buy old clocks that the shop had in abundance. To me the pistol on the table looked like a small air rifle that had been cut down and fitted to a pistol stock. It wasn’t until I returned to the States and started learning about airguns that the genuineness of the BSF S20 pistol was discovered. I had lived for 3 years and 9 months in Erlangen, the city that was home to the famous airgun manufacturer Bayerische Sportwaffenfabrik (BSF) without realizing it!

Veteran readers of this blog know that I have already reported on the S20 Custom Match version of this pistol. That pistol shares a lot with this one, but the trigger adjustments on the Custom Match are different (and finer, I believe), as are the sights, front and rear. And the grip on the match pistol is more contoured in a target style, where this one is plainer. It’s what the Germans would call a sport grip. But the basic powerplant parts are the same on both pistols.

BSF S20 trigger adjustment
The trigger adjustment is one screw in the back of the end cap.

Finding the gun

I found this pistol on an auction website, along with several other nice airguns. I’ve already told you a lot about the Mauser 300 SL I found there, but there is still a BSA Airsporter Mark I report coming. The pistol we are examining today was priced low enough that it attracted my interest, and the competition was not strong. I put in a bid and won it for even less than I was prepared to pay — mostly because I think I was the only bidder who knew what it was! That’s where owning a copy of the Blue Book of Airguns pays off big time.

Some faults

The pistol came with some faults that were pointed out in the auction listing. The rear sight is missing its adjustable notch, the right grip panel screw was missing and the escutcheon on the right side of the grip was gone. I need to find or make a rear sight notch and I don’t know what to do about the escutcheon, but I had a replacement grip screw in the S20 Match pistol box. So that was fixed right away.

BSF S20 rear sight
Rear sight is missing the sliding notch. It should be easy to make.

The listing also mentioned that the gun shot with low power, but that’s where a knowledge of vintage airguns comes in handy. I know that both the breech seal and piston seal in this pistol are made of leather. I can make them easily, plus they were probably dry and might respond to a good oiling. When I got the gun I was proven right about the oiling. I oiled both seals and the pistol’s power perked up!

Not so simple

Despite its appearance, the S20 is not the simple air pistol it appears to be. Nor is it a cut-down spring rifle like I first thought. It’s more of an air pistol that was designed by men who built air rifles for a living. It features a rear sight that adjusts for elevation and an adjustable trigger. The lockup at the breech is bank-vault tight, yet it pops open with ease when you want it to. The pistol looks like it will be hard to cock, yet I find it relatively easy for the power of the gun. That’s because of a long piston stroke.

BSF S20 cocked
The piston has a long stroke for power without hard cocking force. Notice the missing right grip escutcheon.


The BSF S20 is a large breakbarrel air pistol. It’s 14-3/8-inches long by 5-1/2-inches high. The barrel is 6-7/8-inches long. It weighs 2 lbs. 6 oz. which, while substantial, is not overly heavy. The barreled action is all blued steel and the stock is a one-piece pistol grip made of what appears to be light blonde walnut. This is an airgun from the classic days of post World War II.

The S20 was apparently not imported by either Air Rifle Headquarters or the Beeman company. Both sold the S20 Custom Match model, but perhaps they both felt the standard S20 competed with the Weihrauch model HW70 too much. I don’t know why it wasn’t sold by them, but it makes this model harder to find in the U.S. than the more sophisticated Custom Match version.

What to do next?

I have already put a screw in the grip. I need to make a rear sight slider and I need to test the pistol for power. If it’s low I will disassemble it and rebuild it. I have the performance of my S20 Custom Match to compare to.

Next for this blog will be a test of the velocity. That will be followed by a decision of whether to repair the rear sight or overhaul the powerplant next.

47 thoughts on “BSF S20 air pistol: Part 1”

  1. BB,

    What a nice little gem! No, it is not 100%, but it will not take much to get it in fine shooting trim. This will be another one of those interesting blogs to follow. 🙂

  2. B.B.,

    I had a moment of panic since there was no blog to read during my lunch break, until I realized that you guys have probably gone into Daylight Saving Time over there.

    From where the screw adjustment is placed for the trigger weight I would hazard to guess that this changes the sear engagement to lighten the pull.


    • Siraniko,

      Yes, Daylight Saving Time kicked in Sunday.

      I think you might be right about the sear engagement adjustment. That seems to be how BSF always does it. And their triggers are known to become so smooth that they will slip and fire. I have a pellet hole in the ceiling of my office to prove it! A BSF S55N I have did that. This is one trigger that you never want to grease with moly!


  3. Familiar looking pistol, thanks for sharing BB. Ive had a few Chinese copies of these in the past.

    I’ve just returned from my first proper airgun event. Forty or fifty people freezing to death in a cold field! Loved it, got to shoot and handle airguns I’ve never even heard of. The oldest was a 250 year old airgun with an octagonal barrel and a metal butt which contained an air reservoir. Didn’t get to fire that one, but I did fire many others.

    Came back with a crossman 1377, and a couple of plinkers for the collection. Brought a tune up kit for my 97 blackline, hoping it’s something I can manage with my lousy skills. Sold a few vintage pellets and other bits there, so wife didn’t object to much!

    I didn’t realise how huge a difference tuning can make, but having handled tuned and untuned airguns I can certainly testify to the difference.

    I also got to fire our hosts Chinese B2. It’s been modified to become basically a recoilless gun, a wonderful thing to shoot. Can’t claim to understand exactly what he’s done, but I was impressed.

    Next event will consist of much more shooting and a lot less drinking! I was shaking so much I could hardly hit a thing!


    • Hi Rick,
      I’m very surprised that you seem to be unaware or choose to disregard one of the cardinel rules when handling firearms or any gun for that matter. ” Never take alcohol, do drugs or take medications that can affect your ability, when handling weapons. It’s an open invitation for a ” Stupident “.

        • Errol,

          Please believe I would never mix alcohol with guns or anything else. The beers came out after the guns had gone away!

          Yep it was absolutely freezing Tom, coldest night so far this year. Well worth it tho!



      • Rick
        My sincere apologies. I should have known better. I genuinely wanted to prevent a very dangerous situation. Please don’t misunderstand. I recently had to reprimand my best friend & prevent him from handling his BT 65 cos he had a few beers and wanted to go hunt hare! I had to remind him of all the rules again.

  4. B.B.,

    That is looking like a rare pistol to find. Casual perusal through various searches has failed me in finding a picture online of what the rear sight originally looked like. Every one of the leads have shown the pistol with the rear target sights mounted. I could imagine that it is something that can slide up and down the groove to change the elevation with a sliding blade locked by a screw for windage.


  5. B.B.,

    That’s one beautiful air pistol! I’ve seen vintage breakbarrel pistols before, mostly Dianas, but this is by far the most elegant of them. That grip looks like it would just melt in the shooter’s hand. And I am always strongly drawn to figured wood. Very classy.


  6. B.B.,

    Unrelated, but the subject came up in a conversation I had yesterday, and I was not 100 percent confident of my answer. I was asked how the distance in most competitive shooting events was measured. Obviously the target on one end. I said I believed the distance is from the muzzle. The fellow I spoke with thought it was from the shooter’s eyes.

    Now I fear I was incorrect, however.

    Thanks in advance for your answer.



    • Michael,

      It’s always supposed to be from the muzzle. In rifle matches it’s easier to gauge. In pistol matches the larger shooters with longer arms do get closer than those who are smaller, but the difference is so minute that even the Olympics ignores it. This happens because the firing line is kept straight.


    • 6.5,

      I will test one if AirForce International makes it available. I was talking to them about testing one some time back and they weren’t satisfied with the trigger at the time. They were not importing the rifle until they could get the trigger they wanted. I know their engineer was working on some design modifications they were going to send to the maker.

      Maybe that has been accomplished?


  7. One of the best things about PA’s Airgun Academy blog is that I almost always learn something new from reading it.

    Like the word escutcheon for example. I am going to try and work that one in to conversation at least twice a day from here on out.

  8. On the general subject of collecting, I’ve found a whole new world as part of my re-enactment interest. There is a company called International Military Antiques that offers the darnedest things for sale. There are plenty of period firearms from the American Civil War and earlier going for over $3000. But what caught my attention was the instrument panel of a Boeing B-17 for $5,000! Where the heck would you put that?

    Sirinako, how interesting, though not surprising, that others have wondered about converting airgun distances to the equivalent in firearms. Do you have a reference for this Capstick article? I wonder what his assumptions were for his comparisons. I would tend to agree with your two examples. Hitting a one inch target with an air gun at 100 yards is just about impossible, so I would call that the same as hitting a firearms target at 3000 yards. And I can believe that hitting a casing at 32 yards with a 10 meter rifle would be like 1000 yard shooting. Using my B30 in .177 with 900fps, I was able to hit the case of a shotshell on the berm at the 50 yard line offhand. But that was after many repeated attempts. You could call it volley fire.

    A comparison of velocities is the starting point, I would think, but not enough for a full comparison. Also relevant would be the difference in energy with the lower weight of the airgun projectile and the more significant effect of air drag on the pellet. These would work generally to increase the firearms distances relative to airguns from a starting point based on velocities. But it would be interesting to see the Capstick methodology.


    • Matt61
      I love mini-sniping at multiple distances with different size targets and guns.

      Been doing alot of that with airguns and most recently alot with different rimfire rounds out of my stainless action/black synthetic stock bolt action Savage with my most favorite Hawke sidewinder scope.

      I have multiple size homemade and store bought steel spinners in my yard from 20 yards out to 100 yards. It’s kind of like a mini-sniping field target course. 10 different targets at different distances. So basically I take one shot at each target with each gun I pick to shoot. And yes I even do my .177 Tx 200 out to 100 yards. Talk’n Kentucky windage definitely defines the Tx when I stretch it out.

      But yep my one inch homemade spinner at 50 yards can be almost as hard as as a 2″ spinner at 80 yards. And I have to end my reply with the accurate guns are the ones that make me shake my head in amazement when that steel spinner rings at distance whatever size target it may be. 🙂

  9. BB:

    I’m going to ask a question that I have been wondering about for a while. I know (and use) the artillery hold on the rare occasion that I shoot my break barrel rifle. The question: Is there any special hold for a break barrel pistol?



      • BB:

        I’m sure that you list of blog topics is a mile or two long but I would appreciate you added it to the end of the list.

        I almost bought some type of Chinese break barrel pistol a while back (looked a lot like the one in this blog but definitely a Chinese knock-off) but didn’t because the guy said that he couldn’t hit the side of the barn with it from the inside of the barn. I wondered at the time if there was a special way to hold the pistol and if that was the problem. I also thought that $50 was too much for it.


  10. BB, another favorite of mine! The S20 was actually the first “serious” European spring-piston gun I was ever exposed to–a friend of mine had one in junior-high days. I’d find excuses to visit his house, just so I could shoot it! For many years, it had the reputation of being the hardest-shooting air pistol to be had, and I always admired its elegant, slender design–a light and nicely balanced pistol in spite of its considerable length.

    The biggest difference between the standard and target versions of the S20, was the long cylinder plug with fully-adjustable sight on the latter, which replaced the simple ramp sight and flat plug on the standard gun. This change also moved the trigger-adjusting screw. Oh the standard gun it is in the back face as your photo clearly shows, and impinges directly upon the sear; on the target versions it is under the sight plug and rather weirdly works at an angle.

    A version of the S20 was sold for many years with the target sight and standard-style grip; I have two of these. I think the thumb-rest grip of the S20 Match came along fairly late in the gun’s life. As you noted, the standard version seems to be the hardest to find, though.

    I have read (though can’t prove it) that the S20 actually was developed from a junior-size rifle that BSF manufactured. The strongest evidence of this may be the “bullpupped” trigger design. As you know, this uses a rather Rube Goldberg-ish linkage to reach from the blade back to the sear, peeking out the back of the grip/frame along the way!

    I will look forward to further installments of this one!

      • My dad moved recently and cleaned out his garage and gave me boxes of old tools, and in one of the boxes was one of these BSF s20’s. I really want to try to get this thing working again. At first the barrel wouldn’t break open due to so much rust. Some wd 40 over night did the trick and now it is opening almost all the way to the trigger guard, but is not locking open. Thanks this site and a few other blogs and forums I was able to disassemble it without too much headache so far. The only problem is I don’t see anything wrong with any of the internal parts. I’m actually suprised by how clean it is on the inside. The only thing I’ve noticed is the cocking lever it think it’s called is very slightly bent, as well as the part at the back of the gun with the small spring is slightly bent. There really isn’t a ton of info on these things and was wondering if anyone has had the same problem. Or has any idea what is going on with this air gun?


  11. So I’ve got my mods20 completely taken apart. Was able to straighten the bent cocking lever somewhat although not perfect. Going to also straighten up the bent sear I think it’s called. Any other ideas? Should I smooth and polish and regrease parts? If so does anyone know what products to use?

    • forseng,

      Welcome to the blog.

      You are in luck. The BSF S20 breech seal is leather. Read these reports:



      I can’t find the exact report where I cut the leather seal out of a leather belt, but these reports should give you the idea of how that’s done.


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