Brocock .22 Sniper Magnum-How To Increase Velocity?

[Kopfjaeger]

I just recently purchased a Brocock .22 Sniper Magnum and shot some H&N 25.31g Rabbit Magnum slugs with some interesting results.

On the highest power level-4 the average velocity is about 865 fps and they are spiraling about 4" diameter at 70 yds

On power level-3 the average velocity is about 830 fps and they are spiraling about 8" - 10" diameter at 70 yds

On power level-2 the average velocity is about 740 fps and they are spiraling 2 to 3 feet at 70 yds!!! I didn't even bother with power level-1

So it looks like the faster they go, the spiraling decreases. I wanted to increase the velocity to see if I can get these to fly true. I have increased the hammer spring tension by turning the screw in 2 full turns, with no change in velocity. The threads on the screw are very coarse, two turns is about 1/4" 

The factory setting for the reg is 165 bar.....Is the only way to increase velocity on this gun by increasing reg pressure?

There is a headless screw in the center of the hammer that is barely past flush with the face of the hammer. This is what strikes the valve stem. It seems to me that if I lengthen this screw, it will open the valve sooner/longer as the hammer travels forward releasing more air before the hammer "body" contacts the housing?? If this is the case, anyone know what the max distance it can protrude from the face of the hammer before it damages the valve?

Any insight is greatly appreciated!! TIA

 

[Skip-in-WV]

Remove the stock. On the left side you will see the hammer. It has 2 screws. One keeps the hammer from falling out. The other permits adjusting a striker (like the one in a Marauder). The striker can be adjusted to change the velocity.

Another way is to put a spacer behind the hammer spring.

 

[Kopfjaeger]

Ok, so adjusting the striker does effect velocity....is there a max distance I should be concerned with the striker protruding past the hammer face, before it damages the valve assembly??

I understand the spacer trick to increase spring tension...as I stated I did increase the hammer spring tension by screwing in the hammer screw about 1/4" with no effect on velocity.

Maybe it needs more tension, I figured a 1/4" in would show some sort of increase???

 

[Bob_O]

A 1/4" adjustment was likely way too much.

A 1/4 turn might have resulted in an improvement.

 

[Kopfjaeger]

I should clarify, the 1/4" in was the max I went. I tried 1/2 turn increments up to the 1/4" depth with no change in velocity.