Have just been working on an early 3 digit B series .177 gun, a basic strip, washer set and re-lube plus normal checks. On re-assembly the gun was doing 620 fps with AA fields, and was very accurate and consistent after only 100 shots

However......620 seemed a bit low for me, so I have tried both Webley GP's and Eley Wasps.....What a difference!...velocity jumped straight up to 720+ with each of the latter, and the gun was noticeably smoother and quieter (it sound like improved piston cushioning when switching to the older style pellets).

I have shot pellet sensitive older guns before, and always try all sorts in my older BSA's, normally of course the .22 guns are the pain as the bores were 5.6 not 5.5, but in .177 I have never seen such a variation (I have chronoed a 90 shot string, 30 of each type to be sure about this).

In my own older .177 guns (mostly BSA) Air Arms Fields normally are very very good, and superior at longer ranges to the old style shorter diablo types. The pellets when compared , (ie. fields against G.P.s) come up very close dimensionally, within a couple of thou, so can't quite get my head around this.

weights are around 8.5g for the AA's, 7.4g for the Wasps, 7.9g for the Webleys, so as a percentage the slightly lighter weights of the pellets from the period of the gun cannot account solely for this (16% increase in velocity for 7% reduction in weight in the case of the G.P's).

Skirt blow out and sealing may come in to it I suppose, as maybe hardness / deformability , but I must admit I am surprised at the difference in velocity / power!

Anyway, end of waffle.........what do you guys use that you have tested to give the best accuracy (up to 6 yards) and power.......long range is not an issue, the gun needs to be accurate and up to say 10 pounds ish power wise at 6 yards to trigger a re-settable target