A number of years ago, our gun club became affiliated with the CMP. We obtained M-1 rifles and carbines plus many cases of surplus ammo for both.
During youth training with the carbines, we opened a new can with bandoleers of Lake city 69 dated ammo. While charging magazines, a very odd flat nosed showed up. Only one in that I noticed out of all the 1080rd cans we used up.
The cartridge in question weighs 5 grains more than normal loaded one do, and you can see the ogive and nose are completely different. I wonder how much extra pressure that extra 5 grains would develop on firing. As you can see both rds have a bulge where the bottom of the bullet was seated not quite square with the case, probably not that uncommon with issue ammo.
It's anyone guess as to how that bullet got mixed in with the regular ones at Lake City Ammunition Plant.