I have shot a LOT of Korean surplus ammo through my M1s. FWIW, the last time I went to J&G I bought five thousand rounds of it. Prior to that I had fired several more cases (3-4 at least). None that I ever had was Berdan primed.
Yes, I have reloaded the cases, but not many. I am not handloading them until the supply of the loaded stuff runs out and I still have a lot of it left. When I shoot this stuff up, I will buy more if it is still available. But, I have thousands of those cases that have been sized/deprimed, primer crimp removed, primer pockets uniformed, flash hole deburred, and trimmed waiting patiently for the day I need them.
The only two things I have found are that the primer pockets are off center in most of the cases, although this hasn't caused me any problems as far as depriming the cases (this isn't all that unusual, it is no worse than PMC brass). And, the cases are very long. When you trim them after the first firing, you trim a lot of metal off to meet US standards.
FWIW, I shot in a match last April where you shoot steel plates out to 800 yards from field positions. Half the match from a firing line at known distance targets, the other half is a trail walk with unknown distance targets against the clock including reloads. I used a bone stock CMP M1 (Greek) and Korean ammo to win the match.
Two years in a row I went five for five at 700 yards using that Korean stuff.
