I did some quick measurements this evening on some barrel diameters, at the muzzle.

I also measured a couple of 1903 'banded' front-sight bases that came off of something?

1. Original 22" Krag model 1898 carbine barrel - .653 inch diameter, just back of the muzzle/crown.

2. 1896 Krag rifle barrel, cut down to 22" with a Springfield 1903 front-sight. Barrel diameter is .655", just in front of sight band.

3. 1903 Springfield barrel cut to 21". I filed a 'step' on this barrel. 'Step' diameter is .650" to accept 1903 'banded' front-sight.

Two used 1903 Springfield front sight bases were measured:

1. Inside diameter varied from .642" to .648".

2. Inside diameter varied from .647" to .648".