I think the ultimate is probably a mixture, but I'm not so sure internals are all that. I think my biggest gains have been in the trigger, and the stock fit. The tune by Mr Murphy certainly feels better than the standard long stroke, and i don't think that's a bad thing... i'm just not convinced that swapping to something similar but different is going to gain me much inside.
Put it this way, if someone said "this doesn't shift" then i'd be happy with that as a basis.
It's not just us, i spoke to Linus at the worlds and he saw the same as I, in the heat it shot low, in the cool it shot high... but he blamed it on humidity between areas, which I disproved to myself later by seeing it in the same area, the only issue being 10 degrees of temp change.
Anyway... (cos i've got a theory on that to test)... i think most of my gains have been a combination. I've done a lot of work on the pistol grip fit to get my hand sitting on it as neutral as possible within reason. But i picked up a standard mk3 at the club the other day in a walnut AA stock and it shot lovely... no where near as brutal as mine, and while i didn't see the pellet go, I did see the strike on the kill with ease. I'm wondering if the rubber butt pad is giving that feeling.
So as well as going into the internals, i'm going to look at the stock again... i think a couple of inches is coming off the back, and probably the front is getting some serious cutting for something more adjustable. Mean while I'm going to try this quick test for the temp shift, and go from there.
The HW97 has been really shortened, so we're now seeing if that's stable.
Roll on the PJC