Originally Posted by Tikkamike
I have a buddy who was recently given a rifle and has no idea what it is. its a very heavy .308 caliber barrel on a winchester action and a target style stock. but no designation anywhere on the rifle. its a long action and the bolt face is .540 so I am assuming its a 300 win what was used for bench rest back in the day. I told him to go have a gunsmith run a go/nogo 300 win in it and see if its head spaced for that, that would at least get us in the ball park, but those are head spaced off the belt right? so it may be an old wildcat or something. If he had someone take a mould of the chamber we would know is that the only way to find out? is there a way to do it himself?
If he has some new or fired 300win brass, he could see if the brass would chamber, then add a thickness of scotch tape to the head. It might take 3-4 thicknesses to create a 'no-go'.
If I suspected it was a 300win and didn't have a gauge, I'd give the above a shot to get a better idea.
I'd probably drop a .308 BULLET in and measure the distance into the chamber the rifleing started. This would give me a rough idea of possible cartridges.
As far as the scotch tape method. I use a go gauge and 2 pieces of scotch tape on the head as a no go when fitting Savage barrels.