It's always going to be cheaper and easier to find ammo to feed the 9.
Even in a SHTF scenario the ammo most likely recovered will be 9mm pistol, .223 rifle and 12 gauge shotgun shells.
JMHO
Even in a SHTF scenario the ammo most likely recovered will be 9mm pistol, .223 rifle and 12 gauge shotgun shells.
JMHO