The most accurate revolver I ever shot was an old S&W military and police, I believe they were called. The Barrel had just a tiny and quite abrupt bevel so it wouldn't shave lead. I never found a load that didn't shoot well in it.
The huge throats being put into modern revolvers allow cast bullets to swell way oversize than have to be sized back down, and it isn't good for accuracy. In fact if someone ignorantly loads very soft lead bullets to high pressures in them it has split the barrel and frame on quite a few guns.
I would put maybe a two degree included angle in there, and do it on the lathe, after zeroing the bore to be sure it was running concentric. I wouldn't cut the diameter at the start more than .010 over groove diameter. Do your boring with a razor sharp boring bar, then polish the leade taper with emery paper till it glistens. Of coarse the stub would be single point threaded in the same setup, with threads that were free enough to allow the frame to screw on without too much force, and with the bare hands. With the barrel stub threaded, length can be determined. Ideal cylinder gap is .002 on every caliber from 22 up to 44, so I don't see reason to believe 45 would be different. With a .002 gap, any lead spray you might get will blow out easily, but most important is the sound you'll hear. This size gap lets just enough powder gases out to soften the muzzle blast. Less gap and blast from the muzzle will be increased, while more gap and blast from the gap will increase. At .006 gap and larger, the blast will give me a headache, even with top quality hearing muffs on.
To keep the barrel from ever loosening, locktite it with the permanent type. It will never move, and will require considerable heat if you ever want to remove it. If you torque the barrel in like the manufactures do, you'll get the typical bore constriction at the threads. The above eliminates it.
Ideal cylinder throat diameter is .001 over groove if you intend to shoot mild loads exclusively, .002 if you want to run it at full power a lot.
Understand that ANY cutting, drilling, tapping on the outside of the barrel will change the inside in some way, so plan on minor lapping after you have the whole thing screwed together. If you have the skill to point it right, you'll have a precision shooter like you never believed possible.
