>>27737262.25 ACP +P+ CCW polymer handgun. Quad stacked mag (or maybe two double stacks front-to-back?) that holds 30 rounds. Make it about the size of a compact glock, and have a "military and police use" version that fires in 1200rpm.
Basically a modernized Lercker Pistol, remade in polymer to keep the weight down and with an over-sized mag to make up for it's small caliber. However, even Standard FMJ .25 ACP loadings actually manage to reach 14" of penetration in ballistics gel, so I imagine a +P+ loading could make a hollow-point reach 14" as well.
Also, for "tactical" uses, an operator version could be introduced that uses a tiny suppressor like the Beretta bobcat used in this video:
https://www.youtube.com/watch?v=V3tBLlEKoXQ. OR, a special .25 "quiet" cartridge could be produced which has a piston inside the casing that upon firing shoots the bullet out and seals in the gases, make the entire gun completely quiet (other than the racking of the slide of course).
Imagine; a concealable automatic pistol that can dump 30 rounds into a target in under 1.5 seconds in almost complete silence.
