bumping the power on a 707 ultra 9 mm??

Alright, here’s the deal; right now i’m shooting .360 000 buckshot at around 840/850 feet per second.
Since the o rings on the bolt probe blew i took the whole gun apart, to fix the rings, shim the bolt and polish whatever wasn’t smooth, causing the o rings to be cut up while loading rounds.

Now, i had a good look at the way the gun works as well, and knowing that you can increase the power on a fire 201 by replacing the hammerspring or adding preload to that spring, i started to wonder how to get these roundballs flying at 900 or 950 feet per second. (no powerwheel in a 201, so adding preload to the hammerspring of a 201 definately works)

Right now i can shoot 3 clips before the POI shifts at 50 yards. I would be perfectly happy if i can bump the speed to said velocities and get 12 consistant hard shots (2 clips) instead of 18 at lower velocities.

My question is; is it possible to bump the speed with this particular gun by just adding preload to the main spring? This because the hammer will only be able to travel a certain distance before the powerwheel stops it from moving forward… This might sound a bit vague, but the guys that know these guns will understand what i’m talking about

I’m not looking for ‘crazy power’ since these guns aren’t that solidly build, but my gut feeling says that all parts should be able to take a little extra power.

any input most appreciated, cheers, vincent