Not to hijack this at all but was anybody else impressed with the fact that the 9mm can did just as well as some of the others? and that leads to another question. does anyone else know how well a 9mm would work on a 5.56 or if it would last long term on a rifle like a 300blk or 5.56?
No, that makes perfect sense.
9mm cans are designed to work with lower-pressure gasses with are exactly what a subsonic 300 BLK produces.
The problem comes when you heat up those aluminum cans with multiple or fast shooting, nevermind the much higher pressures from supersonic rifle rounds. A typical 9mm can is not long for the world on supersonic rifle use, could be very dangerous.