But, a 25-06 will chamber in a 30-06.....A 30-06 won't chamber in a 25-06, so it wouldn't be a problem. the problems come in where the bullet is bigger than the bore but small enough to chamber Cartridges such as a 270 necked up to 7mm likely fall into that category. It's best if the head stamp does match what the cartridge is.
Initially I assumed you had bought new and they were a factory mistake.I bought a couple hundred of them used-glad I sorted them by headstamp. Fully agree with you and feel foolish that I didn’t come up with the answer myself!
30/06 to 270 ok.
30/06 to 280 rem very dangerous.
reason being that 280 has 0.050 longer headspace than 30/06 or 270.
bruce.