The late Frank de Haas recounted in his original 1st edition gunsmithing book on rifle actions the tale of the American who bought a surplus Type 38 Arisaka rifle (6.5X50mm cal) and as he couldn't get any ammo bought a 30-06 chamber reamer and ground the pilot down so it would fit the 6.5mm bore and rechambered the rifle to 30-06.
He proceeded to fire 30-06 ammo down it and killed a deer or two, even.
As it kicked 'real hard', he took it to a local gunsmith to have it checked over. The gunsmith couldn't believe the rifle had remained intact and sent it and the fired brass to the US NRA technical department who confirmed it was a 30-06 behind a 6.5mm bore and had apparently been fired using 30 cal ammo and put it into their exhibit of horrors. De Haas uses it to illustrate how strong the Arisaka actions were before describing a torture test he and a friend carried out on a 7.7mm Type 77 Arisaka (0.303/0.311 bore / groove diameters) which they rechambered to 30-06 and tried to blow up with increasingly heavy loads such as a case-full of Hercules 2400 behind a 180gn bullet, but failed. (They managed to bulge the barrel and make it jump a tenon thread and comprehensively demolished the case, but the only damage to the action itself was the extractor blown off, He says the action was rebuilt and later incorporated into a hunting rifle.)
More recently, there was a pic around of a 300 AAC Blackout bullet fired in a 223 Rem and the rather (!!) swaged down and lengthened bullet recovered from the front two inches of the barrel where it had finally stopped.
300 aac fired in 223 « Search Results « Daily Bulletin
Unlike the 30-06/6.5mm and similar that require monumental ignorance and stupidity, it's all too easy to load and fire 300 Blackout in 223 it seems.