My old 8 X 57 Mauser is the really old .318 caliber (known as "I" but more often refered to as "J") rather than the more modern .323 or S caliber. I intend to rechamber to 8 X 60 or 8 X 64 but need a reamer with the tighter throat. Anyone have one I can borrow or rent? This is a shoestring budget project and I hate to buy a reamer to only use one time. Duane Wiebe is doing the work.

Why couldn't you use a standard removable pilot reamer and just use the correct bushing? You'd be able to use .323" bullets in the new larger throat.

The barrel bore is .318 caliber.

Yes, but if you get a pilot bushing sized for your .318 bore you can use it.

For example, I reamed a .308 Winchester chamber and the standard pilot is usually .300" but the barrel I used required the use of a .2985" pilot. You could do the same. I would but not all are comfortable doing this with a .005" mismatch.

If you need a reamer made, try Dave Manson or Dave Kiff.

Poleax, I'll bring it up with Duane as I don't know alot much about gunsmithing. Perhaps he can do as you suggest.