I'm a newbie when it comes to Glocks. Shot a buddies 21 after it had some trigger work and liked it. I already have a 1911 .45. I was looking at a P226 Sig Sauer mainly because .357 sig to 40 cal is just a simple barrel swap. Does this hold true on Glocks? Can you buy a G31 and simply install a G22 barrel? If not is there a model/setup that requires nothing more than just swapping barrels?