One of the umpteen awesome things about Firefly is the selection of firearms. Because the aesthetic is a melange of everything from Old West and British Colonial up to Starship Troopers, just about anything looks right. It must be a great excuse to dust off those old pieces that have been lying unloved in the darkest corners of some gun-rental house's vault.
PRODUCTION DESIGNER: "Hey, guys, got anything kinda...different? We're arming some ship-jacker/chop-shop types."
GUN WRANGLER: "How's about a Webley Mk.6, a Browning Hi-Power Mk.2, and a Vigneron M2?"
PD: "Sounds good."