Canadian Airgun Forum

some reason wit the reg at 120 bar and spring cracked full on my m11 mk2 only getting like 550 fps....what should my reg be set at for low fps ?

Are you wanting high power or low? If low, I would reduce the reg AND the hammer spring.

ok but if i wanted it high isnt 120 bar good and with the spring cranked full shouldnt it be shooting way higher....doesnt seem right

120 bar...spring full 620 fps max

For higher power, 135 bar would be even better, most likely, with hammer balanced for that pressure.
Back the spring off a turn and re-test at current reg setting. Is this a .25 or .22?
If you get the same or a little higher speed, back it off another turn and chronograph.

I don't have and M11, but the principal is the same as my reg guns. Once the reg is installed the volume of air behind the reg can be referred to as the plenum even thought is not a physical plenum. With the volume air being so small you need a higher pressure to achieve the same results. With no reg the whole tube is the plenum and all the volume of air is available with no restriction. If you had installed a spacer between the valve and the reg then the volume of available air would be greater and the velocity would increase even though the pressure is unchanged. When you purchase a Lane reg. for a bottle gun you are able to order a spacer for your plenum volume. In one of my guns I used PVC conduit as the reg spacer.

I hope I have made myself clear in such a short statement of a complex issue.

Best to all.
Robert