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Bill · New Member

Could someone be kind enough to point me towards an airgun smith who could work on a project with me.

This involves slowing the velocity of a spring piston air rifle from 340fps to somewhere in the 250fps range. Thanks, Bill.

Slavia · Moderator

What's your intended purpose? 340 FPS is already pretty slow.

Robw · Veteran Member

I have no idea why anyone would want to do such a thing but you could either
cut mainspring spring coils or reduce/restrict the transfer port size.

I would hazard to guess that reducing transfer port size would be the best way
to go as I believe that would get you the velocity you want and still keep a
decent velocity spread and thus, accuracy.

Bill · New Member

I'm hesitant to go into the details but it goes like this.

I'm from the centerfire community and I shoot Benchrest competition with a 6PPC. In that environment three of the variables we juggle to gain accuracy is with barrels, bullets and load variations.

All of those variables can be transferred to air rifles. Not all shot tubes and not all projectiles (BB's in this case) are created equal. And on a positive note we're not trying to shoot .250" groups at 100 yards. We're only looking at 10 meters.

Just assume for a moment that there is an unlimited budget and unlimited time to invest in the project. If you varied the velocity you would/could effect group size. So the plunger spring wire size and winding would make the projectile go faster or slower. With the right speed you can find the sweet spot that would be short of the projectile rattling down the smooth bore shot tube.

If I were an airsmith, which I certainly am not; I would have the plunger spring and shot tube from an accurate and a non accurate spring piston design side by side. And just for curiosity I would make modifications just to learn something about the process that I didn't know before.

Understand that the latter would be changes for the sake of changes. Just to prove or disprove a theory. Not many people would even waste a minute much less a dime in taking this on.

I would be looking for the following things.
- Determine OD/ID of the two different plunger springs.
- Buy or modify the plunger spring to reduce fps in the poor accuracy rifle.
- Slug each shot tube to see the quality of each bore.
- Replace the poor shooting shot tube with a proven quality shot tube.

I'm pretty spoiled by 40 years of hand loading centerfire rifles. To me there's no such thing as rifle that can not be made to shoot more accurately. Now a 35 Remington with hand cast bullets can't shoot as accurate as a 6PPC but a 6" group at 50 yards with a lever action 35 Rem can be brought down to 3". In this case I'm looking for dime sized groups at 10 meters.

I've been assured that the Avanti 499 will do that for me. And when they get back in stock I'm sure I'll add that and I'll probably find a used 99 to add to my collection as well. But I'm too stubborn to walk away from any project that shoots half dollar size groups at 10 meters.

For some reason I feel I have to justify that I'm not a crackpot. I took on an RWS 48 a couple years ago and at the end I was able to put pellet next to pellet at 20 yards firing one shot a day at the same target over 5 days. Basically the dime size group with a cold barrel that I was looking for. This was done using bench rest shooting practices modified for a springer and doing the proper search for which pellet to shoot.

Sorry for dragging this out and thanks for letting me vent. Take care, Bill.

shawn706 · Member

PM sent Bill.