JC- interesting observations and thoughts. About the shallow rifling and bullet/ball alloy.
Taylor's Shilo Sharps, a .45 3-1/4" bought eons ago, had .0015" rifling depth. Yeah - 1 1/2 thou. We tried for about 7 years to find a load it would shoot. Up until that time, he did use the rifle for hunting moose, but had to use jacketed bullets with black powder and was rewarded with amazing accuracy - watch him shoot it - as small as 3/8" 3 shot groups at 100 meters (several such groups in a row) with tang and globed pin-head using 500gr. Hornady RNs & 100gr. 2F.
We tried bullets as hard as we could cast, even using high speed Babbitt at about 28Brinel, then oven heated/quenched & hardened WW running even a bit more than that as well as everything in between pure lead and Babbitt - both paper patched and groove & lubed. Nothing would shoot except those jacketed bullets. Moose died but we still couldn't find a cast load to shoot - from 400gr. to 540gr.
THEN, I bought "The Paper Jacket" - read it, made some suggestions and we were then successful. Taylor's reground a drill, bored out an old smaller calibre mould and cast up some 400gr. pure lead, well-undersized bullets. We wrapped them in masking tape and we had a 1 1/8" 5 shot grouping rifle with cast bullets and black powder. We also tried normal paper patching as well as larger bullets but that particular rifle wanted that truncated cone 400gr. FN wrapped in masking tape. My own .45 3 1/4" at the time, a Hoch barreled Rolling block liked normal paper patching and a 580gr. from a 4 cavity mould we re-cut. Both these successful bullet combinations were pure lead, and when patched, ran .451" at the most, barely touching the rifling when loaded. They could be each be shot up to 20 times without cleaning without any loss in accuracy. A single dry patch wiped all the fouling from the bore - there was no buildup. We used lube balls as per the book's directions - beeswax/Vas also rubbed on the paper patches.
I surmise the BP loads effectively obturated the bullets to the bottoms of the grooves just about instantly upon ignition - gripping the bottom of the grooves as hard as possible and reamining hard pressed due to the pressure behind. Neither barrel fouled - we were elated - of course.
The results we obtained were polar opposite to the normal thought of the day, in that as hard as possible is necessary for shallow rifling - it looked that way due to the jacketed experience, but the undersized, pure lead wrapped in paper proved there are generally other possibilities.
