Hi all.
Just pulled my qb78 to bits to have a look and thought the transfer port breech gasket could be better, so how about this.
6 to 8mm 5mm brass tube (id 4mm)
Open the valve body transfer port to 5mm (it was about 4.5 as standard)
Open the breech transfer hole (the one just below the barrel) to 5mm
Chamfer the inside of the brass tube that fits inside the valve body to aid flow.
When the tube is seated in the valve body it should fit in the breech flush with the inside so it doesn't tear the barrel seals when the barrel is replaced.
I put a silicone washer around the tube between the breech and the gas tube, but not entirely sure it needs it.
Put it back together, job done and no need for replacement breech gaskets.
Hope that makes some sense. You can get the tube from model steam engine stores (maccmodels in the uk)
Cheers all
d
