QB78 help

[BeerJam]

I understand your problem accessing valve, but this showing all the signs of a valve stem head that's come loose.

If that is the case, I have successfully replaced a valve stem assembly without complete disassembly. So long as the valve body seal is in good order, the valve internals can be withdrawn and replaced with access from the filler cap .

For any sceptics out there, this repair lasted many months and was still good when the next strip down was performed .

Cheers, Mark

[goathead]

Anyone got a favourite guide to stripping these guns? I cant resist tinkering.
Cheers,
Halam

[radiofan]

It may seem obvious, but make sure you are not resting the gun on the barrel. This will definitely affect your grouping (drove me nuts BTW).

If you have a modified pin-type probe, it is possible that as the bolt wears, it puts more sideways pressure on the pellet as you push it in. This can deform the skirt of thin-skirted pellets like the AA-Field and the pellet then fails to grip the rifling. Thick skirted pellets do better in this situation, like FTT or Bisley LRG.

Finally, if the gun has gone over-power, you will get shot-gun like groupings. I think this is because of the relatively fast twist-rate of these barrels, which were originally designed for lower power. I suggest you take off the silencer and measure the power with a chronograph.