..bleive they put the barrel/breech assembly together (glue) and then drill the transfer port. Only way that makes sense considering the burr. Not too hard to cure, and once the barrel breech area is burr-free, they seem to shoot quite well.
To do that lap work, had to have remove the bolt. While i've not had nay problem with mine, can't help but notice how thin the bolt is and how larger the tapped hole for the locking part of the bolt. Not a lot of metal left around that tapped hole, and I'd suspect that the occasional bolt has failed at that thin spot. I'd avoid spring settings that require strong/yanking bolt opening.
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