Dave Tooley his rightly stated that no pressure is produced so no danger. I think the danger is complacency. I had two identical rifles one in 6mm and one 25-06. I put 6mm ammo in the 25-06 it didn't fire but it was sloppy. Sloppy can get you in trouble, like when you put a magazine of 300BLK in a 223 rifle and chamber up a round and fire it. This kind of poor rifle handling has happened to the best of us, but we would be well served to think better and safer and not do this kind of sloppy stuff. the more we model safe gun handling the more common place it will become.