Thanks Harvey - I cannot actually make the hammer spring any weaker on this set up, as it wouldn't be able to pierce the CO2 cartridge! It is only just piercing it at the moment. I went through about 5 iterations of different spring/guide/top hat configurations before I settled on this one. It's just strong enough to set the trigger at half cock, and as far as I can tell there is very little hammer bounce when it is gassed. No farting noises

However I am currently making a Stopped Spring Guide (SSG) which user Gerard showed us a link to the other day (see the thread lower down, Crosmsn 2240 tune for more shot count), which apparently has had superb results with increasing shot count and consistency. Multiple people have managed to wrest the best part of 100 shots (!) from a single cartridge....The idea is that it has minus preload, so the spring runs around a guide that has a top hat built in so that at rest, it sits a mil or so away from the hammer. This is said to almost completely eliminate both hammer bounce and the power curve, giving 90+ consistent shots before dropping off rapidly.

So I'm in the middle of building one of these, and I've had an idea that will prevent it from being able to be turned up to beyond 6 ft/lb (always a risk with power adjusters) - I'm going to use a threaded rod, and braze a nut to the end that projects from the rear of the pistol. At the hammer end I will cut the end of the rod off when I have reached the perfect length, and loctite the stop nut. I'm also going to braze a tube on the outside of the rear plug to both act as a guide and to tidy it up a bit aesthetically.
I have another scrappy 2240 that I can test this all on before tearing this one down again.


I suspect it may be able to get a few more than 35 shots at the moment though, but that is as far as I have tested it at this stage. Those 35 (-ish, I wasn't taking notes) shots were at full power without noticeable drop-off. I'll be taking it up the range next week and making notes, and shooting semi-serious cards rested, so I can see exactly what it is capable of.
The trigger unit is all completely aftermarket and there are no crosman parts inside it. It's a pseudo two-stage but very crisp.