How to make a spring-piston air rifle shoot smooth: Part 2
by Tom Gaylord
Writing as B.B. Pelletier
The Benjamin Legacy SE.
This report covers:
- The rifle
- Important point!
- The chase
- Cocking effort
Today’s report should make an interesting contrast to the work I have been doing on Geo791’s Diana RWS 34P. By the end of this report I think you will see that American airgun manufacturers have the ability to make world-class spring guns. Let’s get right to it.
Now I’ll tell you a little about the gun we have been looking at. The Legacy SE looks a lot like Benjamin Trail rifles. There’s no Weaver scope base because the Legacy SE was made years before Crosman began putting Weaver bases on their Trail rifles. What it does have is a set of conventional 11mm dovetail grooves with a single hole at the back for a vertical scope stop pin. Given the extreme smoothness and lack of recoil, that was good enough. There are no open sights.
The trigger appears to be the same one that’s found in today’s Trail guns; and since it isn’t holding back as much force, it breaks very crisply in stage 2. The safety is manual, so the shooter is in control, which is how I like it.
The cocking effort is exactly 16 lbs. I know because I’ve measured it for this report.
The rifle is normal-sized, at 44 inches overall. What looks like the barrel is just under 20 inches long, but the actual barrel is hidden deep inside a shroud. The actual barrel is about 1-1/2 inches shorter, and there are no baffles in front of it. The muzzle brake is just a nice solid cap that completes the look of the rifle.The pull is 14 inches.
The stock is synthetic with a dipped woodlands camo pattern in deep woods green and gray. There’s a stylized thumbhole, and the stock makes the rifle completely ambidextrous. A dark rubber cheekpiece is pinned to the top of the straight comb. The buttpad is a ventilated black rubber pad that prevents the rifle from slipping when stood in the corner. The forearm is thin in cross section and flat on the bottom for a good hand rest.
The metal parts are not polished and present a matte surface for the black oxide. The metal barrel jacket is even duller than the spring tube. There are a few plastic parts on the gun, like the triggerguard and end cap, but the trigger blade is metal.
The barrel pivot is a screw that can be tightened. That means the rifle can be very accurate because any sideplay can be removed. However in testing mine wasn’t that accurate. I discovered that the end cap on the muzzle brake was probably touching the pellets as they exited the muzzle, tipping them sideways. The 25-yard groups were all over one inch.
The pellets were flying sideways, causing an open group.
As I told you in Part 1, the Benjamin Legacy SE did not last long. Rather than go on about what didn’t happen, let’s look at what did. Ed Schultz used what was learned from the Legacy SE as a starting point to develop the Crosman NPSS (Nitro Piston Short Stroke) — the rifle that got everything right! Same idea — easy cocking and smooth shooting, but with more power. How much more? Let’s look.
Crosman Premiers — 712 f.p.s. with a spread from 695 to 727.
RWS Superdomes — 694 f.p.s. with a spread from 680 to 709.
RWS Hobbys — 771 f.p.s, with a spread from 761 to 781.
Air Arms domes — 673 f.p.s with a spread from 664 to 679.
Crosman’s NPSS is no longer made, but was a landmark rifle in its day.
The cocking effort was no longer 16 lbs. like the Legacy SE. It had increased to 24 lbs., but was still lighter than any other gas spring air rifle at the time. Now we had good power and easy cocking — a world-beater combination!
The trigger on the NPSS rifle breaks at 3 lbs. 12 oz. and is so crisp that I guessed the weight was a pound less. The length of the stage one pull is adjustable, but the letoff weight doesn’t seem to change with adjustment.
This is where the rubber meets the road. Because, if the rifle isn’t accurate, nothing else matters very much. This NPSS is quite accurate.
Five JSB Exact RS pellets went into this 0.302-inch group at 25 yards!
The accuracy may have a lot to do with the NPSS having a pivot bolt instead of a pin. The breech can be tightened to eliminate sideplay. But pivot bolts aren’t common on such airguns. Plain pins are far more common, to keep the manufacturing costs down.
I can just imagine the corporate meeting in which this design feature was discussed. The money guy asked, “How much does a bolt really help the accuracy? A bolt, plus the subsequent additional machining (threading the receiver fork) and additional assembly time costs the factory 31 cents more than a plain pin that can be pressed in. By the time that cost flows through our marketing model it adds $1.29 to the retail price of the gun. Is this pivot bolt really necessary?”
If there is an Ed Schultz sitting at the table (as there was for the NPSS), he can explain how the bolt helps the rifle maintain superior accuracy by allowing the barrel pivot tension to be adjusted. He knows this, not because he is an engineer, but because he is also an experienced airgunner.
If the engineer at the table doesn’t know the answer, the bolt goes away and the pin is substituted. Don’t blame the money guy — he’s just doing his job. The question he asked was reasonable. The problem was the engineer at the table didn’t know the answer and could not defend the more expensive bolt.
So, the rifle that gets the plain pin sells 11,000 pieces over the next 10 years, where the same rifle, if it had a pivot bolt, might have sold 50,000 pieces. But that is a subtlety that few people understand.
The NPSS went on to become the Nitro Piston 2 (NP2). That’s a gas spring rifle with even more power and additional technology (a buttoned piston) to reduce vibration.
I wrote this 2-part report because of the test I did on the Umarex Throttle. That rifle contains a device called Stop Shox to calm the firing cycle while still producing excellent power. In this 2-part report I have shown you the evolution of a gas spring rifle that needs no technology to produce the same result — with incredible accuracy!
If a manufacturer were to provide a gas spring rifle that the user could fill, then what you see here might be possible again. Let’s hope such a thing is being designed.