Anyone Figure Out How to Adjust the Velocity of Hammerli AP20's?

[Gwhite]

A local club with an active junior program has an AP20 that is shooting a bit slow. I don't think they've measured it, so I'm guessing this is based on the report being softer than the other AP20's they have, or it's making ragged holes in targets.

There have been a couple of queries about this quite a while back, but never any specific answers. Unlike most air pistols, the force of the striker spring that controls the opening of the firing valve doesn't appear to have any adjustment capability. The pressure regulator is literally a black box (well, more of a trapezoid...) that isn't broken down further in any of the exploded diagrams. It's possible there is a pressure adjustment feature in it somewhere, but it's not described in the manual.

I have heard anecdotes that the velocity of AP20's can change over time, and I took baseline data on the 26 pistols we have for the college team I help coach. So far, they've all been fine, but if one starts to get feeble, it would be nice to know if there is anything we can do about it. We have a spare regulator we can swap in, but beyond that, it would have to go back to Walther.

Thanks!

[David M]

Buy a new hammer spring and compare the length, old vs new.
You could try a shim or two under the old spring and use a chronograph to see if the velocity changes.

[Gwhite]

Thanks! I thought about fudging the striker spring arrangement. Unless someone left it cocked for a long time, I wouldn't expect the spring to take a 'set".

It looks like getting the striker spring out isn't exactly trivial. On a lot of other PCP's, it's pretty straightforward.