Re: .308 round out of .270 rifle
I saw the results of this exact mistake a few years ago in New York. A hunter loaded .308 cartridges in his Ruger M77 Mk II lightweight in .270 Win. He fired the rifle, and the rifle was destroyed. The bullet did exit the barrel, at a velocity I can only imagine. The Ruger wented the gas into the magazine well, which expanded it sideways and split the stock (walnut stock) in 2. The magazine box is pretty stiff spring steel, and it was bowed out on both sides. The bolt could not be opened with a hammer. The shooter got some stuff in his eye, because he was not wearing glasses. Had he been wearing glasses, he would have been uninjured. He probably ruined his underwear! I did not see it happen, but I did get a good, long look at the rifle afterwards.