BSF S54 underlever: Part 2
by Tom Gaylord
Writing as B.B. Pelletier
BSF S54 Match air rifle
This report covers:
- Some updates — SILE stock
- Adjustable trigger
- Front sight hood
- Rear peep sight/scope base
- RWS Superpoint pellets
- Air Arms Falcon pellets
- RWS Diabolo Basic pellets
- Cocking effort
- What have I learned?
Some updates — SILE stock
Blog readers Kevin Lentz and Mike Driskill asked whether or not the BSF S54 stock had the marking SILE on it. This one does. It’s at the top of the pistol grip, just behind the back of the spring tube.
The stock is marked “SILE.” Mike Driskill says many of the S54s he has seen have this mark.
I mentioned that the trigger is adjustable. The adjustment directions can be found on the bottom of the triggerguard.
The + and – signs tell you what you’re doing to the trigger-pull.
Front sight hood
I left the front sight hood out of the full photo of the gun in part 1, so I’m showing it here.
There’s the hood that covers the front sight.
Rear peep sight/scope base
I also mentioned the rear sight base that can be used as a scope base but didn’t show it in detail. Blog reader GunFun 1 asked about it, so I’m showing it today.
This base is for a peep sight, but it’ll work for a scope. The wear at the rear tells us this rifle once had a peep installed.
Today, we’re going to look at the velocity of the rifle. It’s a .177 from 1979 and has both a leather piston seal and a loading tap, so I thought lighter-weight pellets would go in the low 600s. Because of the tap, I have to use pellets with thin skirts, so the air blast can enlarge them while they remain in the tap.
RWS Superpoint pellets
I have very little experience with loading taps on .177-caliber rifles. Most of the taploading rifles I’ve tested over the years have been .22 caliber. Only the BSA Airsporter Stutzen and the BSA Airsporter that Don Robinson built have been .177s. But the .22 Superpoint is my favorite pellet for taploaders of that caliber, so I thought why not test the .177 Superpoint in this rifle. Superpoints are medium weight, so I expected a velocity of around 550-575 f.p.s.
RWS Superpoints averaged 679 f.p.s.! That’s 100 f.p.s. faster than expected. I guess my .22-caliber S54 was more tired than I thought, because it was what I based my expectations on. The lowest velocity I saw with this pellet was 673 f.p.s., and the highest was 691 f.p.s. That made the spread 18 f.p.s., which was also tighter than expected. At the average velocity, this 8.2-grain pellet produced — well, you should know the answer right away. The magic velocity number is 671 f.p.s. — the speed at which the weight of the pellet in grains equals the muzzle energy in foot pounds. So, at 679 f.p.s. this 8.2-grain pellet produces 8.4 foot-pounds of energy at the muzzle.
Larry Hannush told me he thought this rifle might never have been sold since it had the original hang tag with the serial number on it when he acquired it. If that’s the case, it may not have had as many as 100 shots in its entire 36-year life! This may be what a buyer could have expected from a BSF S54 back in 1979, although we’re still a couple decades away from the premium pellets that exist today.
Knowing that the piston has a leather seal, I put about 10 drops of silicone chamber oil into the air transfer port several weeks ago, closed it and let it drain back and soak into the leather. There was a faint smell of burned oil with the first 20 shots in today’s test, then I think it stopped. Or maybe I just got used to it — hard to tell. We know that all spring-piston guns in this power class diesel with every shot. Cardew proved that in the 1970s through testing. So, that oil, which keeps the leather seal supple and sealing, has to be replenished often.
Air Arms Falcon pellets
Knowing how powerful the rifle is, I’m better able to predict how fast the next pellet will go. I chose an Air Arms Falcon for my next pellet. At 7.33 grains, I expected them to top 700 f.p.s., although not by much. They averaged 715 f.p.s. and ranged from a low of 703 f.p.s. on the first shot to a high of 725 f.p.s. on shot 10. The spread is 22 f.p.s. At the average velocity, this pellet generates 8.32 foot-pounds.
RWS Diabolo Basic pellets
The last pellet I tested was the RWS Diabolo Basic — a less-expensive wadcutter that weighs the same 7 grains as the RWS Hobby. Normally, I’d shoot Hobbys for my lightweight pellet, but I wanted to change things a bit.
Basics averaged 711 f.p.s., so not even as fast as the slightly heavier Falcons. But they ranged from a low of 697 f.p.s. to a high of 728 f.p.s., so the 31 f.p.s. spread was the largest of all the pellets tested. I think that indicates this pellet isn’t suited to the loading tap. At the average velocity, the Basic pellet generates 7.86 foot-pounds of energy at the muzzle.
The cocking lever requires very little effort through the first half of its arc. Only after the midpoint is passed does the effort start to spike. At the max, the rifle requires 37 lbs. of effort to cock. That is about the same as a broken-in Beeman R1.
But as you cock the lever, the loading tap remains closed. It must be opened by hand to load a pellet. That means that the cocking lever can be returned to the locked position, where it’s out of the way while you load the pellet. This feature makes this kind of spring rifle inherently safer to load, because there’s no danger of a beartrap accident.
But the trigger can be pulled with the lever open and the gun will fire — closing the lever as rapidly as the piston moves forward. So, there’s no protection from unsafe handling, like we find in most modern airguns.
The trigger is two-stage. Mine registerd 3 lbs., 3 oz. for stage one and 5 lbs., 6 oz. at the release. I turned the adjustment screw out about 2 turns and dropped the stage two release to 3 lbs., 15 oz. The release is fairly crisp, and I’ve mentioned before that these BSF triggers do break in. So, I’m not going to adjust this one any lighter. Time and use will take care of that.
What have I learned?
This BSF S54 surprised me in a couple ways. The first was its high velocity. I guess these big guns had more going for them than I thought. I knew the S55 and S70 sporters were little powerhouses, and this is the same set of parts, but made to work with a loading tap. I suppose I should have guessed its power better.
I’m used to new BSF triggers, because my S70 came to me with a bent barrel and hadn’t been shot very much. These triggers start out heavy, though not as rough as some others. But with use, they smooth up like a vintage Webley pistol trigger. You feel the trigger blade move but there’s no hesitation, so the release is always smooth.
I’ll be very interested in the level of accuracy this rifle produces. I plan to test it first at 10 meters because it’s a target rifle by design. I’ll keep an eye peeled for a BSF rear aperture match sight to go with the gun. My only concern is that sometimes people with such sights price them as high as entire air rifles, and I won’t pay that much. An AirForce peep sight would be the right height for this rifle, and they’re available for a reasonable price. If the rifle shows potential, I’ll do something about the sights, though I don’t think I’ll scope it.