I'll offer up a counter thought to Emu's theory - I think it is more the specific barrel and the harmonics from the tune that are the reason than the lock time or anything such as that related to the firing valve mechanisms . . . .
I say that having a .22 Huben that is very accurate in the big scheme of things, but the most accurate shooter I have is a .22 Daystate Air Ranger that left the factory in a 50 FPE configuration, but that I have tuned down to about 30 FPE. This gun is more accurate than my Huben, a purpose built benchrest Bottled .22 Marauder (with dual regulators and a WAR valve for an insanely tight ES and an LW Poly barrel) and another regulated Marauder with a Jim Gaska barrel - but here is the thing: with this Air Ranger being a detuned 50 FPE gun, it is running a +100 gram hammer with reduced spring loads, and thus is the slowest lock time gun of the bunch (with the Huben being the fastest). But it out shoots all the others in terms of ultimate accuracy on paper. The ergonomics are great on it too, so I'm sure that helps a lot as well. An d it also does not fire out the magazine, which does reduce a source of variability (that I'll admit does not seem to impact Emu's Sidewinder much - but a full mag group might be interesting; my Huben does about 0.85" ctc at 55 yards).
Bottom line - it is not just about the air firing mechanism. Every gun's barrel is unique, and when you find a great one, never let it go . . .
With that, I am done and have no intention of getting swept up in the pissing match going on within this post . . .