Airsporter/Mercury power problem

[Shed tuner]

leaking someplace... o-ring heads need a very true cylinder to seal, far less forgiving than a lipped parachute style - as above maybe the cyldinder is dented / bulged / scored

[LESS THAN FORTUITOUS KENNETH]

The tap seems fine. It does point to a problem with the cylinder. Or the transfer port?

[mrto]

8ftlbs is common in later mark .22 Airsporters the MK1 and MK2 are typically better powered.

[peddy]

8ftlbs is common in later mark .22 Airsporters the MK1 and MK2 are typically better powered.

Would have thought around the 500fps to be expected, not many British guns made much more. It's more important that the cock and firing cycle is smooth and twang free and it is consistent. I've tried everything to get my Webley hawk mk2 to make 10fpe apart from machine the piston and the best I could get is 8fpe, but it's now virtually recoil free smooth to fire and very accurate. It's only going to be used for plinking so power isn't priority