Project355
Member
- Joined
- Aug 2, 2020
- Messages
- 672
I think we're on the same page. You can't really "adjust" or "set" the gap by adjusting the bushing. You can only adjust endshake by adjusting the bushing. The gap must be "adjusted" by facing the back of the barrel, and recutting the forcing cone.
.... jogging memories from the 1980s.... the work I did on a not-too-special Colt, I guess a second generation. I really wasn't too much into the generational thing back then. Very very loose. First thing was headspace was checked. It was rim thickness plus a few .001's, maybe .005ish. I thought that was ok. Next a new, longer bushing was gotten from Colt. Took forever. The bushing got depressed into the cylinder, and I measured the protrusion at the star. How to cut it... needed maybe .010 or .011 taken off. I made up a little base pin surrogate for the surface grinder.* Ground off the excess. Now the pin was flush with the star. Fit the bushing into the frame, it wont go. Use the same fixture to trim the front of the bushing, starting with .002 then .001 and .0005 (which is easily doable on the surface grinder, assuming you have things nice and clean). Bushing fit, but cylinder gap was way way to large. Barrel off, came off easily. Turn the back of the barrel exactly one thread. Put barrel on. I messed up, and cut the barrel shoulder at 90 degrees on the lathe. Back in in the 4 jaw, I cut almost another thread off, and left an undercut of a few degrees to account for "crush". Barrel barrel back on. Measure rotational angle, convert to linear distance according to screw pitch. Back in the 4 jaw, take a bit more off, allowing for .004 crush. Barrel on. Lines up. Sticks past cylinder face. Take time to gauge cylinder to make sure its not wavy. Its good. Start to face the back of the barrel a bit at a time until it barely fits. Take off a little more... a little more... and gap is .004. Good enuf. Recut forcing cone. Done. My moldmaker friend did help with the fixture for the bushing, and I think I remember seeing a surrogate bushing that fit on the base pin while in the frame, and it had adjustable length. You'd put it in place, tighten it up front to back, and lock the setting. You could then remove it and you'd know how long to cut the front of the bushing once the back was even with the star on the cylinder. I did not have that, so went nice 'n slow on the surface grinder.
So I think we're on the same page pard.
.... jogging memories from the 1980s.... the work I did on a not-too-special Colt, I guess a second generation. I really wasn't too much into the generational thing back then. Very very loose. First thing was headspace was checked. It was rim thickness plus a few .001's, maybe .005ish. I thought that was ok. Next a new, longer bushing was gotten from Colt. Took forever. The bushing got depressed into the cylinder, and I measured the protrusion at the star. How to cut it... needed maybe .010 or .011 taken off. I made up a little base pin surrogate for the surface grinder.* Ground off the excess. Now the pin was flush with the star. Fit the bushing into the frame, it wont go. Use the same fixture to trim the front of the bushing, starting with .002 then .001 and .0005 (which is easily doable on the surface grinder, assuming you have things nice and clean). Bushing fit, but cylinder gap was way way to large. Barrel off, came off easily. Turn the back of the barrel exactly one thread. Put barrel on. I messed up, and cut the barrel shoulder at 90 degrees on the lathe. Back in in the 4 jaw, I cut almost another thread off, and left an undercut of a few degrees to account for "crush". Barrel barrel back on. Measure rotational angle, convert to linear distance according to screw pitch. Back in the 4 jaw, take a bit more off, allowing for .004 crush. Barrel on. Lines up. Sticks past cylinder face. Take time to gauge cylinder to make sure its not wavy. Its good. Start to face the back of the barrel a bit at a time until it barely fits. Take off a little more... a little more... and gap is .004. Good enuf. Recut forcing cone. Done. My moldmaker friend did help with the fixture for the bushing, and I think I remember seeing a surrogate bushing that fit on the base pin while in the frame, and it had adjustable length. You'd put it in place, tighten it up front to back, and lock the setting. You could then remove it and you'd know how long to cut the front of the bushing once the back was even with the star on the cylinder. I did not have that, so went nice 'n slow on the surface grinder.
So I think we're on the same page pard.
