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Accessories BSF S70 air rifle: Part 2

BSF S70 air rifle: Part 2

by Tom Gaylord
Writing as B.B. Pelletier

BSF S70 rifle is the father of several famous Weirauch models.

Part 1

A history of airguns

This report covers:

  • Today’s the day
  • Oiled the piston seal
  • RWS Hobby
  • Crosman Premier 7.9-grain
  • What’s up?
  • Cocking effort
  • Trigger pull
  • Summary

Today’s the day

Today we find out how honest that Freimark is on my BSF S70 rifle. If you don’t know what Freimark is, read Part 1.

The Freimark is a German airgun mark that denotes a gun that does not exceed 7.5 joules power at the muzzle. That’s 5.53 foot-pounds. That would be a 7-grain RWS Hobby pellet moving 596 f.p.s. That will be our line in the sand.

From my experience with the BSF line, the S55/60/70/80 rifles (same powerplant in all of them) are above 7.5 joules all the time. That doesn’t mean there can’t be some that were made below that level, if German law allows. UK law states that if a model of an airgun can produce over 12 foot-pounds, then ievery one of them must be accompanied by a Firearms Certificate (FAC). They do not allow lower-powered versions of the same model gun to avoid that requirement. In other words, once a certain model needs an FAC, all of that same model need an FAC, regardless of what power they generate. But like I said, I don’t know how the German law reads.

Oiled the piston seal

This rifle has a leather piston seal that needs frequent lubrication. I oiled it with silicone chamber oil and then fired it several times. It did detonate a couple times, then it settled down to shoot normally again. It was ready to test.

RWS Hobby

I jumped right in and tested with the lightest lead pellet that was likely to be around when the BSF S70 was new. A 7-grain RWS Hobby would suffice. Ten Hobbys averaged 657 f.p.s. in this rifle. The spread went from 638 to 669 f.p.s., so 31 f.p.s. At the average velocity this pellet generated 6.71 foot-pounds, or 9.1 joules at the muzzle. Oops — it was over the line. Close, but on the wrong side of the limit.

No judgement yet. Let’s continue and see what happens.

Crosman Premier 7.9-grain

Next up was the 7.9-grain Crosman Premier pellet. This is a good weight for a powerplant of this power level, and the Premier is also accurate in many airguns. Ten Premiers averaged 644 f.p.s., which was faster than expected — given what the Hobbys did. The spread went from 618 f.p.s. to 670 f.p.s., a whopping 52 f.p.s. difference. At the average velocity this pellet generates 7.28 foot-pounds, or 9.87 joules of muzzle energy, which puts it ahead of the Hobby. The theory says the lighter pellet will generate more energy in a springer, so this one is running counter to that.

At this point I noticed that all the stock screws had loosened. This is a common problem with spring guns of this vintage, so you have to watch for it. After they were all tightened, the rifle was noticeably calmer when fired.

RWS Superdomes

Next I tried the RWS Superdome pellet. Weighing 8.3 grains, it is the heaviest pellet I tested in the S70. This pellet averaged 623 f.p.s. at the muzzle, with a spread from 612 f.p.s. to 641 f.p.s. That’s a total of 29 f.p.s.  At the average velocity this pellet produced 7.29 foot-pounds or 9.88 joules at the muzzle. That was the highest energy seen in this test — from the heaviest pellet! Something was backwards, because springers are supposed to do best with the lightest pellets.

What’s up?

Why is this BSF S70 so much less powerful than the other one I tested for you years ago? That one averaged 866 f.p.s. with Hobbys and produced 11.71 foot-pounds or 15.88 joules at the muzzle. You may remember that in Part 1 of this report I said I suspected this one might shoot slower because it didn’t appear to have been worked on. The first rifle had an optional peep sight that Air Rifle Headquarters would install, and I had the feeling that they had sold the rifle.

Cocking effort

Until I look inside I won’t know for certain whether this rifle has been worked on, but the cocking effort for this rifle is 25 pounds, while the effort for the first rifle is 34 pounds. That’s quite a difference! But, is it enough to account for the difference in power? I don’t know. I normally believe a more powerful mainspring does not add any power to a spring piston airgun, but that may not be correct. Or, there may be other modifications to the first gun that account for the additional power. Until I look inside both rifles, I won’t know.

Trigger pull

Okay, it was time to test the trigger pull. BSF triggers are noteworthy for wearing in to the point they become unsafe. I’ve seen it several times. They get to the point that they have to be adjusted as heavy as they will go and even then they are on the ragged edge of unsafe.

This trigger acts like it’s brand new. Unfortunately it is single-stage only, which gives you no feel for the release. You just keep pulling until the rifle fires. There is no creep, but you do feel the trigger blade move as it is pulled. It turned out to be much heavier than I estimated. It broke between 5 lbs. 7 oz. and 5 lbs. 10 oz. I estimated something around 3 lbs. So, I guess the pull is very smooth. I have no desire to adjust it any lighter.


Where we are now is we know the rifle exceeds the legal German limit for power for a Freimarked airgun. But it is not as powerful as the other BSF S70 I tested several years ago. I think that probably means this rifle is stock — exactly as it came from the factory — while the other one has been modified. Maybe I will use the new Rail Lock mainspring compressor on both rifles to find out!

Accuracy testing comes next, though. I will start at 10 meters, using the open sights that came with the rifle.

I have to say this. While this BSF S70 isn’t as smooth or as light as a Diana model 27, it is in the same category, when it comes to quality. A shooter could do a lot worse than to shoot one of these.

author avatar
B.B. Pelletier
Tom Gaylord is known as The Godfather of Airguns™ and has been an airgunner for over a half-century, but it was the Beeman company in the 1970s that awoke a serious interest in airguns. Until then, all he knew were the inexpensive American airguns. Through the pages of the Beeman catalog, he learned about adult airguns for the first time. In 1994, Tom started The Airgun Letter with his wife, Edith. This monthly newsletter was designed to bring serious reports about airguns to the American public. The newsletter and Airgun Revue, a sister magazine about collectible airguns, was published from 1994 until 2002, when Tom started Airgun Illustrated -- the first American newsstand magazine about airguns. Tom worked for three years as technical director at AirForce Airguns, the makers of the Talon, Condor, and Escape precharged air rifles. Today, he writes about airguns and firearms for various publications and websites. He also makes videos, and you'll find short clips embedded in some of his artices on Pyramyd AIR's website. Tom is a consultant to Pyramyd AIR and writes under the name of B.B. Pelletier.

41 thoughts on “BSF S70 air rifle: Part 2”

  1. After shooting the last string with the heaviest pellet, I’m wondering what the MV would be if you went back to the lightest pellet? I’m curious if it was getting better as it was shot a few more times.

  2. Wrong about the UK laws there Tom
    Most of the popular UK rifles have over 12fpe cousins, I have Diana 52’s, HW80’s, 77’s and 95’s etc, not to mention all my PCP’s that are non FAC versions which require no licencing despite having more powerful relatives.
    Ditto Germany

      • Well, they’ve got two sub 12FPE Patriots for sale at my local dealer (gathering dust)
        To be fair, Webley didn’t bother and Hatsan only did for about 2 years, it was unnecessarily weighty for a 12fpe rifle
        The two most popular sporters in the UK are the HW97 and AA TX200, both 15fpe in export markets and by your reasoning FAC only at any power
        The D52 and HW80 are reasonably popular but because of their long stroke are compromised at 12fpe, having lazy actions.
        But no, in the UK it is your responsibility to keep a rifle below 12fpe and any model can be bought

        • Dom,

          Thank you for clearing that for me. Maybe Ivan was just blowing my idea off because he didn’t think much of it. But He explained in detail what I wrote in my report and ever since I have been writing it that way. Oh, well!


          • He was probably right in as much as it would (and probably did) take a bit more than a soft spring to get the power down reliably.
            The D52 has both this and a TP restrictor and is horrible to shoot, I short stroked mine and lightened the piston, removing the TP restrictor and it hovers near jail time now.
            I joke, the airgun power restrictions are, in my experience, almost never policed, and the Friemark thing less so if anything.
            Until about 5 years ago you had variable power screws on the PCP’s simply wound down to 11fpe, though its now usual to have an anti tamper plug.

            • Ironically, there is much to thank the level playing field of set power restrictions for. Without the muzzle energy race the European manufacturers have to define themselves by other means to get market share, fancy blueing, nice triggers, pretty woodwork etc.
              In much the same way as the speed/power restrictions Japan have on their little 400 motorbikes have produced some of the most exotic, swiss watch like two wheelers ever seen.

        • Ivan Hancock was correct he would have run afoul of our UK laws due to the the fact the original Webley Patriot was designed from the ground up as a 25-30 FPE -FAC air rifle, there was no 12 FPE version. In the UK once an air rifle has been registered as an FAC rifle it stays that way no matter the power or even if it’s not working, it’s a firearm once and for all unless deactivated, hence the low price of second hand FAC air rifles in the UK. The pair of sub 12 FPE Patriots are not very Patriotic as they are made in Turkey and are a re-named version of another Hatsan rifle as are the Raiders and Stingrays. Most Hatsan models develop well over our 12 FPE limits for other markets and are barely ticking over for our limits which makes them nothing to write home about as the shooting experience goes, heavy piston, light spring, long stroke, slow and unpleasant, in fact the polar opposite of a good BSF.

          • None of the Webleys are very patriotic I’m afraid these days
            The UK Patriot is (externally) physically identical to the original Webley, including cylinder length and diameter, I don’t think they do it anymore either, physically far too large.
            The Hatsan 55 and 60 (the first Hatsan springers to the UK market) were only warmed over, poorly finished Vulcans, I tried my Vulcans barrel on my Hatsan 60 in the fruitless effort to find accuracy.
            I guess this back compatibility isn’t an issue if the rifle is made outside the UK then?, otherwise the HW80, D52 etc wouldn’t be saleable here.
            By extension Air Arms etc who make identical rifles in different muzzle energies must be forced to make and register a 12fpe version for the home market first and, only then produce a higher power version for export to get past this legislation, so kinda have to go round it that way.
            I don’t think I own a rifle that isn’t available in a higher power version somewhere.

            • To be fair, the Patriot is an awful rifle at any power, no matter where its made now, a Diana 52 will make very similar power with half the cocking effort and twice the accuracy. The Patriot manages to distill pretty much everything I dislike about high power springers into one model.

            • Air Arms designed the TX as a sub 12 ft lbs rifle as a quality made British response to the HW77. The Mk1 TX200 wasn’t designed for export, it had a tiny spring and no safety devices, these are rare as hell now. They also built the wonderful Pro Elite break barrel, mine was awful, 11.8 ft lbs so spot on for UK laws, didn’t creep over the limit with heavy or light pellets and was almost pre charge accurate, it also weighed 11 lbs scoped and the lock time of a flintlock. I traded it back in at no loss at the shop it came from for the Pro sport. I later fired a friends FAC rated Pro Elite and was impressed, at full power it felt like a well tuned sub 12 rifle, only the massive impact and rocket like lock time betrayed it, I wonder where they are now I would love to build a sleeved down 12 ft lbs custom.

  3. I have not played with FPE #’s a lot, but am aware of it and how to calculate it. I thought that the heavier pellet always won out in the FPE category, despite going slower. I may have to go back and look at my TX200 chrony #’s. Hopefully I have some variation in pellet weights that I tried.

    I vote for the dual tear downs. It would be nice to see if you can discern what the differences are between the 2 rifles. Hopefully something will be obvious. On springs, I thought that heavier spring did produce more power, but only up to a given point. Beyond that, nothing. That might be especially true if a less than an optimal spring was used for the sole purpose of bringing the fps down.

    Good Day all,…. Chris

    • Chris,

      I have to agree with you concerning the springs. Now BB’s point of view may be that what he sees is sproingers that are already equipped with the optimal springs and changing that out for a heavier spring only results in a stronger cocking effort.

      Remember GunFun1’s experiment with shortening the spring of one of his sproingers in increments and not losing any power until he had removed a considerable amount of the spring? I am wanting to repeat that experiment this Summer with my Webley Tomahawk. It is an uber magnum sproinger and I want to see how much I can remove without losing any power and see if it calms it down any at the same time. Once I find the sweet spot I am looking for I will have a custom spring made for it.

      • RR,

        You could try starting with 0 pre-load. Gunfun1 went with less than 0,… in other words,.. there was some “slop” at the start. I have thought about making a gauge. A digital bath room scale on which a spring could be compressed. The compression point at which no further spring force was produced,… would be the sweet spot. Just an idea.

        • Chris,

          Good idea. It may work.

          I was actually thinking of doing a blurb on it. I would start with recording performance at stock and at each increment to see how much spring is removed before performance begins to decrease, thus demonstrating how much excessive spring manufacturers install by using “standard” sizes rather than what would be the optimum. I could also elaborate on the shooting “experience” throughout the process.

      • RR,

        Yea,.. I remember that anomaly now that I went back and revisited it. That was all stock. I have the HO kit in now. Prior,.. I tried the 12 fpe kit. Plus a chop. Plus a Torrington bearing. 😉 Yea,.. I have played with it just a wee tad. The HO is it now. Straight kit, no other mods. If I ever do anything again, it will be the bearing on the piston end. You may remember I tested spring rotation under pressure. Less than 3/4 of a twist with full cocking compression. Maybe less. I do not remember for sure.

        Good luck with your Tomahawk.

        • Chris,

          If I can find the proper bearings, I may have to install some in this rifle. I shot it some yesterday evening and although the firing cycle is hard, it is pretty smooth. If I can reduce cocking effort, recoil, trigger pull, etc. and still maintain performance, that would be sweet.

          This looks to be a long term, ongoing project.


    But please be gentle when you do such. You may not desire to keep this one and RidgeRunner’s Home For Wayward Air Rifles has a room available. 😉

  5. I notice that the front sight on your 70 is like the one on my 55. My 70 has a hooded sight which I believe to be a hw sight, which will take inserts. My rifle shoots in the 810 foot per second range.
    My model 55 has the safety on the left side and the model 70 has it on the right. I have had the 55 apart and it does not have a leather piston seal. The model 55 shoots in the 750 foot per second range. I did not change the spring. Thanks again for this article.

    • Bill,

      When you say your 55 do you mean Marksman 55? I can see that one having a Weihrauch front sight. But for a BSF to have one, someone just switched front sights.

      Tes, My S55 averaged around that, I think. I wouldn’t expect a leather seal in a Marksman 55, but I would in a BSF 55.

  6. BB,

    I remember you saying on the early days that .25 cal air guns would only shoot 300-400 fps. I’ve been trying to do some research on this but the Webley Service Rifle is the only one I’ve been able to come up with. Do you know of any others?



  7. On the subject of Germany, I just had a radical new thought. My plan was to ultimately upgrade my shooting outfit at the firearms range to use boots in place of athletic shoes for greater stability. Then, I thought I would combine this with my re-enactment interest by getting original Corcoran WW2 jump boots. Apparently, jump boots have extra reinforcement in the ankles for hard impact which would provide extra support for shooting. But then I thought of another of my collection principles which is to buy the best and most iconic version of each class. So what are the most famous boots of all time? For the modern era, they have to be German jackboots (infamous as they were). They have quite a history in the 20th century and actually go back to much older traditions of riding boots. Plus, they look to have heavy reinforcement in the ankle. So, would they be suitable for shooting? I would think so since they were intended for military use. But my particular goal is to use them for the kneeling position, in addition to standing, and I wonder if they would be suitable for that. I know that most people don’t wear jackboots. But I know that we have a lot of motorcycle riders, and I have the impression that jackboots are commonly used there, getting back to their original purpose as riding boots. Anyway, opinions would be appreciated.

    Gunfun1, if you like ballistics, imagine this scenario. I was reading the memoirs of one of Claire Chennault’s Flying Tigers in WWII, and he described a strafing run on a boat. As he began shooting, he saw his rounds impact on both sides of the boat. As he moved closer, the impacts converged until about 250 yards where they tore out a large glowing red hole in the side of the boat, then they spread out again as he zoomed past. Here is a dramatic visual of how wing-mounted guns in WWII fighter planes were sited to converge at a particular distance. So despite, the speed and power of these planes, the shooting range was actually fairly limited. Imagine the complications of having six guns sited and then having the point of impact further complicated with the moving plane which, when turning, created the so-called deflection shot. One reason the P-38 was so advanced was that its nose-mounted guns didn’t converge and were equally effective at all distances. No doubt this is one of the reasons that this rather strange-looking airplane was considered a forerunner of jet planes.


    • Matt61
      Makes me wonder why they didn’t sight two of the guns for a certain distance then two more for another distance and the last two for another distance.

      But then again they probably didn’t have much time to be locked on a target. Probably more like just sweep the target with mass fire power and hope for hits.

      Oh and them old Mustangs, Spitfires and P40’s have always been my favorite planes. I had one of each I built when I was into the rc plane flying.

  8. Dom is right on UK law. It is the individual gun, not the model, that matters – though I can understand why Ivan might have been reluctant to detune such an obviously over-legal limit gun as a Patriot. It might have attracted some unwelcome scrutiny from the authorities. (A parallel would be the way in the US the BAFTE decides whether semi-auto rifles are “readily convertible” to full-auto, or whether the flash hider on an XM-177 is or is not a noise suppressor.)

    In my experience, a lot of older Freimarked German rifles are a bit over the German limit. It may be that, back in the 70s, manufacturers didn’t pay very close attention to ensuring the every single rifle was under 7.5J, rather than in the rough ballpark – especially in the days before cheap chronographs.

  9. Bear in mind that all the UK spec BSF’s were Friemarked and they were all around 11fpe, so perhaps your previous one was meant for export rather than being specifically modified.
    I know the Friemark was supposed to be a home market legal designation but I’ve actually never seen a BSF rifle without one.
    My feeling is that this one is just a bit tired rather than a home market escapee…..at least that’s more likely.
    The spring does affect power, up to a point, but its limited, ultimately by swept volume, if it didn’t then no airgun would need more than a Biro spring, it’s even more important in older leather sealed models that require a certain amount of detonation from the oily seal to make some of their power (see Gerald Cardew, though now outdated)

  10. My observations on German airguns I’ve purchased directly from Germany are similar to Geezer’s–I don’t think, at least in the early days, the authorities were too rigid in enforcing the Freimark.

    I might speculate that particularly with smaller guns, whose potential power is limited by their limited swept volume, the bureaucrats kinda looked the other way! Diana 27’s I’ve gotten direct from Germany all shoot harder than the limit, but not by any reckless margin. I suspect that guns like this were not manufactured in separate “home” and “export” variants.

    On the other hand, bigger, more powerful guns like the Diana 35, HW 35, FWB 124, etc., were probably looked at a bit closer. You will definitely run into differing OEM power setups on those.

    Pure speculation on my part, but perhaps smaller makers like BSF simply didn’t bother to take the “F in pentagon” mark off their more powerful export variants? They may have kept them separated in the factory by some means simpler than making two versions of the breech blocks.

    • Mike,

      My only experience with this directly is that today the German authorities take the Freimark very seriously. When I worked for AirForce we watched the output of our guns closely. The same for the UK guns we made.


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