I was at the range today and met a guy there that was shooting his new Bushmaster Carbon-15 (the model with the polymer upper and lower). It was a new gun, his second time shooting it, but after just a few shots it jammed on him. When I went to help him clear it I found a jam I've only seen once before.
The live round had managed to jam itself with the rear of the case on top of the bolt up against the gas tube. He tried pulling the charging handle to the rear but all it did was pull the entire live round on top of the bolt inside the upper with the rear of the case jammed against the gas key and the bullet itself jammed against the gas tube.
Obviously we couldn't just separate the upper from the lower because the BCG was stuck halfway in the buffer tube and halfway in the upper. I had to remove the buffer tube assembly, stock end plate, castle nut, etc. to take enough pressure off the BCG to separate the upper and the lower just to clear the live round.
After clearing it and reassembling the lower I noticed that the gas key and gas tube were damaged by the live round. The top of the gas key was bent inward and the gas tube was bent up and edges were bent in. Both were damaged in such a way that the charging handle made contact with the gas tube when reassembling and there was not enough space for the gas key in between the handle and tube so reassembly was impossible. So his jam turned into needing a new gas key and gas tube.
He was using a brass catcher and reloads and thought that had something to do with the jam but I disagreed. My thoughts were that since he was using a standard carbine buffer it was too light causing the BCG to move too fast thus causing bolt bounce; which caused the round to get jammed on top of it. I told him that once he got his gas key and tube replaced he needed to buy an H-buffer from Bravo Company to avoid this again in the future. Hopefully some of yall that know far more than me have seen this type of jam so you at least know what I am talking about.
So what causes this and whats the solution. Am I correct in my thinking?


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