You can have only one version installed at the same time.
.40 SW: Just changed the marking on the barrel from 45 ACP to 40 SW.
9x19mm: Completely remade markings on the slides and the barrel. Now it should stay consistent with its in-game magazine capacity.
.45 ACP: Changed only markings on the slides.
In case anyone is curious (and just so I wouldn't forget it in case I will return to retexturing LEO in the future), fonts: Orbitron for the fancy text like LEO-40 or HS FIREARMS, Arial-like font for other markings.