Which pre-1930 pistol round is best against late-medieval plate armor?

IIRC, some 16th and 17th-Century cuirasses were designed to withstand the firearms of the time - in fact, some armorers would “proof” their breastplates by firing a shot into them as a test, leaving the resulting dent as a mark of quality (hence, “bulletproof”). I don’t know how a musket or pistol round of the period compares to a 1930’s pistol in terms of penetrating ability, though.

He doesn’t yet but he will have one earlier.

It didn’t work.

No, the old .45 was deadly but didnt penetrate well. I’d say the Mauser Broomhandle C96 in 7.63×25mm Mauser, known for going thru BPV.

Yeah, I voted for the original, since it is earlier, but that’s a little faster.

Yeah, about the time they were going for "half’ or “3/4” plate, they made the BP somewhat proof, and with angles.

2-3 mm (~0.1 inch) of mild steel isn’t going to do much to slow the progress of a .45 ACP.

Stranger

Yes, but later BP were 1/4 inch thick and hardened steel. and with slanting a .45 could easily glance off.

What about a 45 Long Colt? that’s been around since the early 1870’s.

About the same. Will penetrate medieval armor, may glance off some of the later armor after early guns.

7.62 x 25 is the answer I’d have given. Though I don’t think they had the steel core bullets for it at the time in 1930. Those really help the Tok zip through things. The Long Colt is interesting, not so much for the round balls that I think a lot of the early cartridges were loaded with, but more for the really long and heavy bullets you can find in that cartridge. 1930 is before Elmer Keith’s time though, isn’t it?

Per Stranger bringing up sectional density, here’s a brief chart of SDs for typical handgun bullets: Handgun Bullet Sectional Density

Welcome Back, Stranger On A Train! It’s been too long, and we’ve missed you.

Finally, I thought the following steel target selection guide might be of interest, since I’ve been finding it difficult to find a ‘handgun bullet vs RHA’ kind of chart: Shooting Targets 7 - Target Selection Guide – ShootingTargets7 Note their warning to keep the velocity below 2850 FPS. Speed kills when it comes to penetration, provided the projectile maintains its integrity. E.g., the penetration of fast, firmly constructed 22-250 bullets at around 4000 FPS plus, is absolutely amazing.