Ok, just had a quick test fire.
1) 0.40's - with almost all the hop applied, it kept the shots flat out to near the target, and then a little ballistic drop right at the end. So although I'd quite like to see how it runs at greater range for-shits-and-giggles, it was always going to a real stretch for it to be usable at full-auto site limits.
2) 0.32's - over-hopped (thought we're talking a gentle upward curve rather than moon-shot stuff, so yeah they're no problem. I'll be running with 0.32s at my next skirmish to see how it performs and whether the slightly more expensive ammo gets better consistency shot-to-shot.
My gut feel was instantly that 0.34's might be worth a go too.
3) Chrono test. I banged a few shots through the chrono just to make sure it was up at the same power levels I had when I last chrono'd (4 weeks ago?). That was 345fps on 0.20's.
Well, it came a s abit of a shock to see 210fps, but then I realised I'd left lots of hop on. Dialed that back, didn't make much difference for the 0.32s, it went up to 220fps. The site limit being 261fps.
So I tried my 0.28's, that came back at 260-265fps - should be nearer 290fps.
It looks like the last couple of skirmishes, where I've pumped somewhere between 5 and 7 thousand BBs (heavy trigger finger!) through it, have taken a toll. It might just need a bit of lube, it might need a new spring. I've got a spare M105 so it'll be a quick job to find out.
(The gun was running great on the field on Saturday though, which goes to show that power ain't everything)
I think that makes my results with the BBs just a 'work-in-progress' because a bit more power might generate a bit more back spin, and hence more lift, but the stock hop unit is fairly decent, I think. (The standard hop rubber... not so much!)
