...I'm betting the seller shot the ammo that came in the can and refilled it with the Chink stuff. To be sure , just pull a bullet and see if it has one flash hole ( USGI ) or two ( CHINK ).
As an aside , I picked up some 30 carb at a show here 2 months ago. A mix of stuff from various venders. Two boxes of this stuff was mixed in with a 50 cal can of LC71. I pulled them and used them for plinking after a sighting in session with my carbines ( have 13 , decided to get serious about having them hit where I aim ). I know most went through the M2 in full auto , but some went through the 3 Wins I had out then. Just by luck , as I was trying groups from all my ammo ( Winchester , PMC , USGI , etc.) , It included some reloaded tracer ammo. I therefore cleaned with WW2 GI bore cleaner in addition to my regular cleaning steps. I'll need to pull these 4 agin tonight to check for rust , but I'm not really worried. I'm more thankfull of this tread because I was able to pull the spent brass from that outing and separate the berdans before it got into the large brass stash for reloading.
Chris