.45 Don.
I have a book that has 14 old gun catalogs from 1859 to 1902 that has a .45-100 Remington necked shell listed and it has the bullet diameter .452"
The Peabody also has .45's listed at .454" and the Ballard .45-100 used a .454"
by the way, They list per 1000 bullets at $8.75
to $16.50 for their special long range patched 1-1/2" long 550 gr
Sharps list one for the .44 1-15/32" 520 gr in their 1879 Catalog.
'"
