Funnily enough, I did some pellet testing on Tuesday evening with my Tau 7 at the range.
Now granted the gun was just rested rather than clamped in vice (but either way 100% steadier than my normal one handed hold ) but the results were :
JSB Schak 4.50 , RWS R10 4.49 and RWS Geco all gave almost identical results through my gun with 6-7 shots out of 10 making one big 1p sized hole with a few wanderers just outside.
Hobby's noticeably opened the group out.
A friend on the next firing point who was doing the same actually got the worst groups by a long way out of the R10's through his Steyr LP10 which he then repeated in vice and got the same result - so they definitely don't suit all barrels...