NitroX,

Measured the bore diameter, appears to be roughly .30 cal, an 8x57JS round drops just past the nose into the bore and sticks without contacting rifling, and a 7mm bullet (280 Remington) drops completely in, only contacting on the edge of the case mouth. Suspecting my caliber reading is off and it may be a .303 caliber? A .308 bullet drops just past the spitzer point to rest on the straight shank of the bullet with some looseness. Thoroughly confused now but it's certainly NOT a 275, and not an 8mm, anyway.