I have a Columbian. It shoots like a shotgun. I slugged the bore. It miked out at .311. I have no idea why. It could be just sloppy tolerances. It was arsenal rechambered to '06 just like the one in the picture. Someday I'll load up a batch of '06 with .303 Brit bullets or 7.62 x 39 bullets and see how it does with the barrel filled out a little better.