Is "hard cast" the same as saying lead? What's the difference in hard cast vs. FMJ when they're each Flat Nose and the same grain size? What would be the advantages/disadvantages of each for what I'm interested in?
As far as the .45 ACP +P is concerned from BuffaloBore here's what they say about their rounds:
"... the two non-expanding loads [230gr. FMJ-FLAT NOSE & 255gr. HARD CAST-FLAT NOSE] are designed to shoot through large shoulder bones or the skull on a black bear. These non-expanding bullets also work well if you need to shoot through cover like car doors or stick frame walls."
Yes, hard cast bullets are lead. "Hard Cast" means that other substances such as antimony have been added to the lead alloy in order to make it harder and thusly reduce barrel fouling at higher velocities and decrease bullet deformation thereby increasing penetration. While the bullets are not made of pure lead, they are a homogenous alloy. FMJ is an abbreviation for "full metal jacket" and means that the bullet's lead core is covered with a jacket made of a harder metal such as copper, brass, nickel, zinc, or mild steel (copper is the most common). Jacketed bullets are not homogenous, rather the lead core and jacket are separate pieces that are bonded together. The issue with shooting cast bullets in a Glock is that the polygonal rifling used in these handguns will accumulate lead deposits very quickly. While this will also happen in a standard cut-rifled barrel, it happens so quickly in a polygonal-rifled barrel that in can cause dangerously increased pressures very rapidly. If you want to shoot cast bullets in a Glock, you should install an aftermarket barrel such as those available from Lone Wolf with standard cut-rifling.