Bsa imp mod d light pattern question

[vbull]

Renovating an old 177 BSA Improved Mod D Light Pattern and would like to know if the cylinder on these are slightly tapered ? The piston on this one seems to get a bit tight towards the breech, it will still slide under it's own weight (without the washer) but is definitely tight at the front end.

[havengore]

I have just put a pair of callipers on mine & there is no tapering on the outside at all…. Maybe there are some effects of dieseling inside yours or even maybe its not the original piston…for the L pattern.... just a thought like….

ATB Simon.

[edbear2]

Renovating an old 177 BSA Improved Mod D Light Pattern and would like to know if the cylinder on these are slightly tapered ? The piston on this one seems to get a bit tight towards the breech, it will still slide under it's own weight (without the washer) but is definitely tight at the front end.

They are normally (and were originally) perfectly Parallel, Maybe vernier the cylinder at various places, and also at 90 degree angles at the same places to check cylinder is round, I have had one in the past where some moron has obviously gripped the gun in a vise by the cylinder, but had used some protection so there were no obvious marks on the outside, this one went stiff when cocking and I had to use a slide hammer to get the piston out

I turned a length of bar to the I.D. and spent an hour or so with a leather faced body spoon, and got it much better so the piston would move freely. The squeezed bit was not in the swept area of the piston so it shot O.K. in the end.

Possibly could be an internal burr or similar as well, all sorts of weird things end up in these over the years

ATB, Ed

[vbull]

Thanks for the above. Can't see anything obvious and the cylinder appears to be round as does the piston head so I'll just lap it in a bit as it's only a slight pinch at the bottom of the travel.