I cleaned my new Long Branch SMLE and got the barrel cast bullet clean. Next job was to determine barrel dimensions. The bore was easy at .3045. I have yet to figure out how to slug the barrel to determine groove. With the shallow two groove rifling, the bullet just want to skate down the bore and I get a .3045 slug. I tried expanding the bullet in the barrel between two rods, but the soft slug won't hold the rifling, but starts to skate on top of the lands when pushed on through. I guess I need to use a hard lead bullet and shoot it just fast enough exist the muzzle and catch it in some soft stuff. But wait..there is an easier way!

Lets ask BruceB and/or other 303 fans. So what is your best guess about groove diameter? I am going to guess .311..take you shot.

It looks like this barrel is going to want hard alloy bullets or else water quenched WW.