A firearm projectile assembly apparatus disclosed herein comprises: a bullet; a hollow core running completely through the bullet from a front of the bullet subassembly to a rear of the bullet; a core material within at least part of the hollow core; and an expansion-inducing tip integral with the core material, and protruding forward of the front of the bullet; wherein: when the projectile assembly impacts with a target, the expansion-inducing tip drives the core material rearward relative to the hollow core, forcing the bullet to expand radially outwardly. Also disclosed for firearm projectile assembly apparatus is a pressure shield; and a non-discarding attachment of the pressure shield to the bullet, such that after the projectile assembly is fired from a firearm, the pressure shield does not discard from the bullet during the bullet's flight to a target. Also disclosed is a pressure shield comprising: a gas check; and various controlled air spaces. Also disclosed are related methods of use and production for the firearm projectile assembly apparatus, and various subassemblies thereof.