I agree - I shoot corrosive ammo all the time in my Garands, Mosins, Mausers etc. BUT - LOTS of battle used (not cleaned properly) rifles did get trashed bores. That is why of the 4 million plus Garands made, almost all of them have replacement barrels on them now and the importance of cleaning thouroughly is why tons of Mosins and Mausers have counterbored muzzles (cause the troops SAWED those clening rods in and out).

No chrome lined barrels in WW2 either.

But as I said - the M1 Carbine was intended from the begining to use non-corrosive ammo (you can't easily take the gas system down and it isn't made of stainless like a Garand's so it won't withstand corrosive ammo) and all US made ammo for it is indeed non-corrosive.