Will a 9mm Luger do the trick?

…d’you mean the cartridge (9mm Luger Parabellum) or an actual Luger P08 sidearm like the Krauts used during the early 20th century? If it’s the latter, you should sell the thing and get a pretty penny for it. (Especially if you have the holster to go with it.)

Otherwise… and I’m going by our old SIG Sauer 226 sidearms here… There’s room for error. Circuitry shots with a 9×19 projectile aren’t unheard of, and they’re wider than a 5.56×45 round… Penetration would be the issue, no? Hollow point rounds! That’s how those ragged bastards at RL would deal with that issue.

TL;DR –

Luger P08 Pistol – Sell
9mm Luger Parabellum round – Unless it’s a hollow point round, don’t bother