Improved model d piston washer assembly advice please

[vbull]

I'm rebuilding an old BSA Improved Model D rifle with a 17" barrel which I guess could make it a light pattern and I notice that the leather piston washer I've just removed, which I doubt is original, is in two pieces, an inner harder disk and the outer. It's in very good condition but the replacement I got from Knibbs does not have the harder inner circular disk of leather as does the one I've removed. Can anyone tell me which type is correct ? Also, the new metal cup washer that came with the leather seal, that the fixing screw goes through, does not appear to have a deep enough relief or dish in it and as a result the screw head is quite a bit proud of the assembled washer set up. My concern is that from it's appearance if fired the screw head will slam into the front end of the cylinder. This can't be correct can it ?

[Garvin]

I'm rebuilding an old BSA Improved Model D rifle with a 17" barrel which I guess could make it a light pattern and I notice that the leather piston washer I've just removed, which I doubt is original, is in two pieces, an inner harder disk and the outer. It's in very good condition but the replacement I got from Knibbs does not have the harder inner circular disk of leather as does the one I've removed. Can anyone tell me which type is correct ? Also, the new metal cup washer that came with the leather seal, that the fixing screw goes through, does not appear to have a deep enough relief or dish in it and as a result the screw head is quite a bit proud of the assembled washer set up. My concern is that from it's appearance if fired the screw head will slam into the front end of the cylinder. This can't be correct can it ?

I don't know if it will help, but there's some discussion of the piston washers here. There should definitely be an inner disc - I think the last one I bought from JK some years ago was green plastic. You're right, the screw head does need to be screwed down below the level of the surrounding leather or it will hit the front end of the cylinder.

[vbull]

Thanks Garvin, that did help. I'm going to deepen the recess on the Knibbs metal countersunk washer so I can get the screw head as flush as possible and use the old inner disk which to me doesn't seem like plastic, more a very hard leather. Do you know how the piston rod comes out, does it unscrew or was it a shrink/press fit with the piston being heated ? I ask because I would like to polish it and while I'm at it do the inside of the piston. I see a very flush fitting screw on the face of the piston so I'm guessing this has to be undone first ?

[vbull]

Old BSA Improved Mod D, thought I'd ask before I ruin it does it unscrew once the flush fitting screw on piston face is removed ? Thanks in advance.

[timewell48]

Old BSA Improved Mod D, thought I'd ask before I ruin it does it unscrew once the flush fitting screw on piston face is removed ? Thanks in advance.

Yes it does, but the keeper screw may well be a bit tight, you need a good fitting screwdriver and perhaps some heat to loosen things.

Good luck!