I've got several hunderd rounds of Korean M2 ball head stamped P8 75. Lot PS-2-162. It is corrosive. I have not shot any in my M1 and I'm not going to. I shot some in a Ruger M77 (old model with the tang safety) and had a full case head seperation. I was wearing safety glases and the lenses were pitted from the gas and particles that blew back in my face. The rifle appears undamaged.
I would be very careful with Korean M2 ball. I would not recommend shooting any in a M1. In fact, I am not going to shoot any more in any rifle I own.
I know CMP is backordered on rifles and ammo, but they still might be the best bet for M2 ball for your M1.
BTW, the ammo shot pretty well in my Ruger ; 3" - 4" five shot groups at 200 meters.