I think it's a good idea to have 357 barrels for at least one of your 40s. 357 SIG ammo has been available at just about everyplace (including the Wal-Marts) around here where there is no other ammo in stock. Having the barrel to drop in may allow you to obtain ammo when your normal calibers are unavailable. Of course, if a lot of folks get the barrels, 357 SIG ammo wil be out of stock just like everything else.