Re: 30-06 reloads
I see you said "30/06s", so I'm guessing "more than one"?
Hawg may have called it right. Or the reverse might be it - some were loaded short so they fit in the magazine of a specific gun. Maybe even the chamber, for one or more guns. I've got two guns in the same caliber, but one chamber is slightly shorter than the other. I can load for one with rounds set to max recommended OAL, but if I load them in the other gun, the nose if the bullet actually gets forced into the rifling. Chamber is, maybe, .010 shorter in that gun.
Or, could be something real simple. They are different bullet weights. An ought six loaded with a 180 grain bullet will have more bullet exposed than one loaded with a 150 grain bullet.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.