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Education / Training BSF S20 air pistol: Part 2

BSF S20 air pistol: Part 2

by Tom Gaylord
Writing as B.B. Pelletier

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

Part 1

A history of airguns

This report covers:

  • Chinese copy?
  • An HW70 copy?
  • Velocity test Premier 7.9-grain
  • RWS Hobbys
  • Crosman Silver Eagle hollowpoints
  • Breech seal?
  • Trigger pull
  • Cocking effort
  • What’s next?

Today we’re going to see what condition my new/old BSF S20 pistol is in. I will compare it to my BSF S20 Custom Match pistol that I tested back in 2008. That pistol is shooting at the rated velocity of 440 f.p.s., for pellets that were never specified in the ARH catalog, so I guess they are Hobbys or something equally light. But before I get into that testing, I have a surprise for you.

Chinese copy?

Reader Richardwales mentioned that he had owned a couple Chinese copies of this pistol in the past. Then reader JimQwerty123 mentioned that he had also considered buying one. I answered that I had allowed $10 in trade on one (a Chinese copy of the S20) at the Findlay airgun show several years ago, and I had always intended testing it for you. Today I’m going to show you that gun and ask both readers if it is the one they were referring to in their comments.

An HW70 copy?

I always thought the Chinese pistol I have looks more like a copy of the HW70 pistol (see the HW 70A pistol) than the BSF S20. And maybe the two readers are talking about a different Chinese pistol than this one. At any rate, I’m using this opportunity to show it to you and to announce that I intend testing it for you one day soon.

BSF S20 Chinese pistol
The Chinese pistol on the bottom looks something like the S20 pistol above. I thought it looked more like an HW 70 pistol, but I can see it either way.

Velocity test Premier 7.9-grain

Back in 2008 the Custom Match shot the Crosman Premier 7.9-grain pellets at an average 398 f.p.s. In this S20 they average 249 f.p.s., which is 149 f.p.s.slower. The velocity spread went from 218 f.p.s. to 275 f.p.s., which is 57 f.p.s. This pistol is clearly in need of some help! This is one big benefit that comes from owning a chronograph, because the pistol felt and sounded strong to me.

RWS Hobbys

The RWS Hobby pellet is often used as a standard for velocity tests because it is so light for a lead pellet. In the S20 Custom Match pistol Hobbys averaged 438 f.p.s. — almost spot-on the 440 f.p.s. the pistol was advertised to get. In the S20 pistol I’m testing today Hobbys average 287 f.p.s., or 149 f.p.s. slower — again! The spread went from a low of 281 f.p.s. to a high of 296 f.p.s., which is 15 f.p.s.

Crosman Silver Eagle hollowpoints

The final pellet I tested in today’s pistol was the Crosman Silver Eagle hollowpoint alloy pellet that is no longer offered. In the Custom Match pistol they averaged 553 f.p.s. In this S20 they averaged 386 f.p.s., or 167 f.p.s. slower. The spread was huge, though! It ran from a low of 290 f.p.s. to a high of 454 f.p.s. That’s 164 f.p.s.

Breech seal?

I noted that the leather breech seal is completely flat with one large divot out of it. It can’t be doing its job very well. I “fluffed” it with a small pick and got Hobbys to shoot about 15 f.p.s. faster than their average. This was just a quick and dirty way to determine that some improvement could be made by replacing the breech seal. It’s not a fix, but it does tell me a new seal is needed.

C20 breech seal
The old leather breech seal is completely flattened and has a divot out of it. Does it still work?

C20 breech seal fluffed
The seal is stuck in the groove pretty tight. So I picked the fiber out of the leather to “fluff” it up a bit, to see if that made it seal better.

I think the piston seal also needs to be examined. And the mainspring might even be a bit tired. Whatever it is, I will address it and see if I can get this pistol back to where it should be.

Trigger pull

The single-stage trigger has a long pull that releases when 4 lbs. 10 oz of effort are applied. Yes, there is a trigger adjustment, but I’m going to wait to see what the trigger mechanism looks like inside the gun before I start adjusting things.

Cocking effort

Most of the cocking stroke is light — at just 14 lbs. throughout the arc. Only at the end of the stroke does the effort spike to 21 lbs.

What’s next?

I think the next step for this pistol is a complete teardown and evaluation of the powerplant. After I see what’s inside I can make better decisions about what should be done next.

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.

32 thoughts on “BSF S20 air pistol: Part 2”

  1. The barrel looks to have some strong rifling.
    Maybe it will group well.

    I too have seen the Chinese pistol here and there, but never bought one.
    Other than the Chinese copy of the FWB 65, none have ever caught my eye.

    The words springer and pistol just shouldn’t be used in conjunction with each other, in my opinion…

  2. BB, when you disassemble please mention how you remove the end cap.
    Now, BB when target shooting I am learning to call shots, I can almost feel which ones will hit bang on and which will miss as soon as I shoot, but most of the missed shots , I am unable to call properly, meaning I called 3′ o clock but it hit 5′ o clock and like that for vertical also. How to be exact?
    While offhand shooting, I mostly form a triangle with my left hand and rib cage, but one of my guns doesn’t like to be held that way. I extended the arm towards the cocking slot , and no with proper stance its better but it is throwing shots sideways a little too often, and I am getting horizontal groups instead of round ones. What I can I do to remedy the situation?
    And lastly, does doing physical exercises help me to become a little better shot?

    • Riki,

      You just need to spend more time at it. A time will come when you call every shot exactly as it goes. The more you concentrate on the front sight, the sooner that will happen.

      As far as your shooting stance goes, I can’t help you. I only shoot handguns one-handed, except in unusual circumstances.

      Yes physical exercise helps you shoot! Especially cardiovascular exercise. I have my resting heart rate at 40 beats per minute. When I’m upright, it’s under 60 bpm. That helps my sighting a lot. Because every heartbeat moves the gun.


  3. Tom, I certainly agree with you that the Chinese pistol looks more like the HW 70, or pre-war type Diana model 5, than the BSF.

    By the way, I believe a cleaned-up version of that particular Chinese design was actually sold by Diana, as their Model 3, for a few years.

    To me, the most unique design feature of the S20 is the trigger and sear. It’s a long and complex “bullpupped” design, since the sear has to reach way back to catch the notched rod protruding from the rear of the piston. Most break-barrel pistols have the sear acting directly on the bottom side of the piston, which keeps the mechanism much shorter and simpler.


    • Mike,

      It looks like you have shown a Custom Match that has the S20 grip. Is that the case? Because the trigger adjustment appears to be under the rear cap instead of inside it. Is the S20 trigger different? I imagine it must be.


      • Tom, yes, this is one of my two S20’s that combine the original simple grip/frame with the target-type rear sight. I’ve actually seen more of these around on the used market, than either the standard pistol, or the later version that added the Match grip.

        I don’t believe there is any significant internal difference between the standard and target gun’s triggers. But as you noted, the trigger adjuster (which is a simple sear-engagement screw) is located differently. On the standard version the screw is located directly behind the sear, on the target guns it works at an angle from below, but does the same job either way.

        • Mike,

          I have never seen a gun like the one you pictured, but now I know that it is an established design. Like you said, it’s an early gun made before the better grips were developed.

          It’s always great to learn something new. Thanks, Mike,


  4. B.B.,

    I have a three of those Chinese pistols. They were closed out at Compasseco for $8 each as I recall. Heavy single-stage trigger, pallet wood, nice steel. I wasn’t able to shoot them accurately, but I was still pretty new to airgunning at the time. An excellent pistol shooter like you might make them group tightly for all I know.

    They dieseled quite a bit and smelled like hamburgers when shot. The boxes for them are almost exactly like the triangle paper boxes pizza places sell individual slices in.

    I bought them to learn basic tuning and maintenance on, but haven’t gotten back to them or even thought of them for years.


  5. Those Chinese pistols were heinous, quite possibly the worst airgun short of a Gat I’ve shot, hopeless accuracy, no power, the sight blade cuts your hand, heavy cocking…I really can’t think of a redeeming feature. The last one I experienced would throw pellets a good foot to the left at 10 feet
    I think its, nominally a copy of a Diana pistol from the seventies…I used to know which one but its fallen from my memory

      • Well, if there’s one thing that’s consistent with Chinese guns its their inconsistency, and with your unusual luck with high fpe (I’ve never seen a Meteor over 9.5fpe or an Airsporter over 10.5fpe, or at least one that behaved) your Chinese pistol will probably group half inch at 50 yards and drop hogs, however the ones I’ve shot had graunchy triggers and no power, I even remember noticing the sight slowly rotating at the front, and it was the barrel

  6. OT.
    Had an interesting experience yesterday. Had a chance to go shooting with one of the members of the Canadian Olympic Biathlon team.
    First…accuracy. Outstanding. Had a state of the art new Anschutz .22. At 50m, standing, no sling,, not support five shots that were just one ragged hole. The thing was the speed. No shoot, carefully aim, shoot again.
    It was just bang, bang, bang, bang, bang. Now he admitted it wouldn’t be quite that good after a 2km ski, but what the heck.
    Second…his training. Runs at least 10km a day. Does a hundred pushups a night with the rifle and gear on his back. At least a hundred dry fires.
    Very impressive.

    • Wow, that must have been fun to watch. Peep sights on a bullseye target?

      I’ve never had a chance to cycle the action on a biathlon rifle. Seems like they’re really slick. Did you get a chance to try the fella’s Anschutz?


      • Yes, he let me put a couple of magazines through it.
        I shot from the bench. But still, shooting at the targets he brought (the bull was about 3″), I got one ‘group’ of three shots in a 1/2 cluster in the middle of the bull…and the other two were easily over an inch or two away.
        But it was amazing to me how accurate it was. Centering the bull in the two circles (from and rear) it just seems a small dot…I was surprised just how easy it was to shoot. And of course the bolt and trigger were both smooth as butter.
        Gotta admit, I am a huge fan of the .22WMR. Way more punch that the LR, yet still fairly cheap to shoot. I have a nice Savage that shoots 1.25moa…but since last night I have looked at the Anschutz website 1/2 dozen times. They have a real nice hunter style .22WMR, that though about 4x the cost of my Savage I just know it would 1/2 my groups.
        Or so I would like to think 😉

        • Sounds like fun!

          Love peep sights. You and B.B. are right: they’re just so natural. Some of my favorite plinking activities involve peeps: 1) spinners with my Walther LGR w/aperture insert at the front, and 2) clay pigeons upon soft berm with the good ol’ M1 Garand. Each very satisfying.

          Must one day take Zimbabwe Ed’s advice and swap an adjustable rear aperture onto the LGR. The teeny olympic rear is very precise, but it needs a lot of light and is maybe not quite as comfy and pointy as, say, the M1’s.


  7. I’m not beyond running a razor across the face of a worn leather seal, removing it, cleaning the groove and then putting a bead of silicon sealant or automotive gasket liquid in there and popping the breech seal back in (it will now sit suitably proud).
    You can get two or three goes out of a leather breech seal this way

  8. BB,

    The bottom gun in the picture looks like the one that I looked at.

    Does the Chinese one in the picture have a pronounced barrel droop? Or is it just my old eyes?



  9. Jan— Thanks for remembering my advice. Let us know how you like the adjustable aperture rear sight, when you get one. Do you have access to a microscope with an iris diaphragm? It is amazing how controlling the amount of light improves the resolving power of a microscope, or a gun sight, or a camera , or a photographic enlarger, etc. —–Ed PS– you are right—I meant to use zimbabwae–ed, but it was late at night, I forgot the hyphen, and I am stuck with zimbabweed. It makes me sound like some kind of plant !

  10. The Chinese one at it’s cheapest price was worth buying just for the rear sight for parts.
    pyramid had some within the last two years,

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