hamer spring discovery

[Ffisher]

I discovered something today. On my Diana Chaser, rifle kit, 22 cal., stock hammer spring, I was getting lower 400 fps. put in a heavier spring and a 1/4" spacer. Crony reading 471 fps. In a different part of this forum someone told me that increasing the hammer spring pressure makes the gun louder but not faster. Well today I stretched the stock hammer spring to 3-1/2" ( recommended on a couple you tube videos). I installed it with no spacer. Boy was I surprised at the crony reading, 525 fps. Blew my mind, LOL. So that tells me that there is a sweet spot in hammer spring pressure. too much spring pressure actually reduces fps. So I'm getting more fps now in 22 cal than factory states fo the177 cal. Now a happy camper. Not only did I increase fps, it is much easier to cock.
Bill

 

[nervoustrig]

Sometimes too much hammer spring tension will overdrive the valve stem and the hammer strikes the back of the valve. The collision causes the hammer to rebound, reducing valve dwell (how long the valve is open) which causes a velocity loss.

However the expectation would be low gas consumption as a result, and that did not seem to be happening in this case (getting only ~170 total fpe per cartridge). So I assume the high consumption was due to hammer bounce.

It will be interesting to see how the new hammer spring does over a full string.