yep, you can swap out a barrel on a g20 and shoot .40 s&w or .357 sig (not from the same barrel)
OR you can get a G21 and shoot .45 acp,
swap a barrel and shoot 10mm
swap a barrel and shoot .40 s&w
swap a barrel and shoot .357
there are other calibers you can shoot too, notably 9x25 dillon and .50 gi!
glocks are pretty damn modular so they are crazy fun! enjoi!
Assumption is the mother of all ****ups.
Know what you know, Know what you don't know. -Paul Pedzolt
"Jack of all trades, master of none, though oftentimes better than master of one" -Mynshul