Are you sure those are your brass? What's the inside dia of those larger neck cases? Since the headstamps match, my first guess is that someone pulled out 25-06 to make 30-06 cases. By my eye, it looks like your smaller mouth case neck would slip right into the mouth of those larger necked cases, and since .25-06 is something on the order of 0.290" OD on the case neck, that'd make them a .30-06. They look to have too much shoulder to be a 338 A square, and too big in the neck to be a 280 or 270.

So that's my vote - someone necked up some 25-06 brass to make 30-06, and somehow they ended up mixed into your batch.