I have a low serial number Krag that I took out of the safe the other day to prep for winter. My new endoscope camera revealed a much better than anticipated bore, better than even my low round count Shilen Select Match 308 barrel.

Almost no firecracking, perfect lands and grooves, very few rust pits. But after cleaning two 308's, I tried to put the same jag and patch down the Krag to oil the bore, and it would not fit! I had to drop down a jag size, and that confused me.

Is the 30-40 bore smaller than the 308 Win?