I’m blanking on what OTC refers to...
All external dimensions of the “.38 Rimless Smokeless” or “ACP” are the same as .38 Super, just not pressure. Your 1903 Pocket Hammer uses a much weaker design. Also I’d avoid a lot of modern jacketed bullets in order to take it easier on the old barrel steel.
.38 Super brass, dies, & shell holders along with cartridge over all length are gonna get you there.
