Krochus,
Yeah, I slugged it, and it came out to .3095, that matched the info that I found online for the rifle (Finnish Mosin Nagant). I figured the .308 would be a good start, as the Sierra book shows the .308 bullet, and my Lee die for the 7.62 sizes the neck to .308. Gets a little confusing with all of the groove diameters for that particular rifle and caliber.
MH