Short stroking my AA S500; or Reducing lock time.

I've had my Air Arms S500 3.5yrs. I've shot with it stick at 18fpe, and tuned for 12fpe. When I tuned it for 12fpe I played around with making a free flight hammer for it. It never worked out, oh well. The 12fpe tune worked very well though, giving me 150 shots on reg from 3,000psi-1500psi.

This past summer I returned the gun to shooting at 18fpe. This involved nothing more than putting the stock hammer and spring back in and turning up the reg. No balancing the valve/hammer/pressure.

A few weeks ago I got the gun out to get it ready for FT and noticed it had leaked down considerably over the last two months. Not hesitating I ordered reseal kits for the gun and regulator, and a couple different bits including hammers/strikers, springs and such to balance out the hammer and valve for best shot count at 18fpe. I disassembled the gun and cleaned it while waiting for parts to come in. I took the time to polish some bits, including the valve stem, hammer guide, hammer and other bits. As I'm terrible at documenting things once I start to work there are no pictures for that so feel free to ask about any parts/work done I may not mention. Anyways on to the title(s).

What made me abandon the free flight hammer idea was realizing there wasn't enough length in the assembly to allow for proper acceleration for the hammer to open the valve enough. One thing I did notice, even back then was that the stock hammer was heavy enough to open the valve with a softer spring than factory. One of the hammers I ordered was for an S410, it's longer than the S500 hammer as you will see in the pictures.

If I may interrupt myself let me try and explain a bit about lock time. In an airgun it's the amount of time it takes the for the hammer to open the valve once the trigger is pulled. The less lock time you have faster the shots goes off. This is important in target shooting because holding on target longer can/will lead to less precise shot placement. The way I accomplished this was to use a longer hammer ahead of the sear catch(S410 hammer) to reduce the distance between the hammer face and valve stem while keeping the spring at it's full length/strength. With the factory hammer there was a noticeable lag between sear break and valve strike. By cutting the striking distance in half, reducing the hammer weight and using the full strength FAC spring That lag is gone. Now when the sear breaks the pellet seem to already be out of the barrel.

Here are a few pictures to help illuminate on the story.

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Thanks for reading. John Also, I'll be getting some shot strings done over the chrony and post the results. As of right now it's shooting about 890fps with 10.3g JSB.177
 
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Thanks guys. ackuric, I've always been able to tune my guns by feel. I know it's far from scientific and if not carefully executed can be dangerous. I never suggest others use my methods either. Next time I have it apart, I will take a few measurements. Heck I might buy some calipers too and post the results here along with a shot string or two.