Bullseye wrote:What is possible is a round of .300 Blk can be accidentally chambered in an AR with a .223 barrel and fired with catastrophic results. Since the .300Blk uses a casing from the .223, with the same external diameter, but is shorter in overall length, it will fit into a .223 magazine and chamber. The 30 cal bullet will not fit into the smaller caliber barrel and this is where the problem would happen.
Would the 300 chamber all the way or would it get stuck and have to get sacked out with a rod? I don't think it would fully chamber.
If the 223/5.56 was fired in the 300, wouldn't it be likely fire form the brass nearly to the 300s dimensions? The pressure would drop off majorly when the bullet left the case since there would not be a gas seal between the bullet and the bore. I've seen 9mm shot out of a 40sw and if it doesn't split the case mouth it look like a reverse bottleneck.