I purchased a rifle some time ago for a song. It has a Mcmillan thumbhole composite stock (not sure why you'd want that on a big bore),2-7x32 Leupold/rings and was built on a Manchester Interarms Whitworth action. The problem however was that the previous owner (who had passed away) loved to wildcat his rifles. Unfortunately, this rifle was unmarked when it was re-chambered (presumably from a .458 Win Mag). All I knew was that it was a .45ish caliber. Some of you may be asking yourself "why would he buy a rifle without knowing the caliber?". Well I figured the parts were worth more than the price I paid, so I nabbed it. Anywho, to save from parting out this rifle and selling it in parts, I would like to attempt to figure out the chambering.

The chamber cast was done using Cerrosafe. The caliber comes up as .458". However, the other dimensions seem to run a bit high over the listed ones dimensions for a .450 Ackley (my best guess for chambering). Could someone offer me any information? Here are my measured dimensions using a digital caliper:

top of the neck: .485"
bottom of neck below shoulder: .490"
shoulder: .505"
right above belt: .519"
belt: .536

It sounds just like mine that I have on a 1917 Enfield. I'll try to post dimensions later.

Here is a cartridge drawing:

Thank you gentlemen

Mine is very similar in dimensions except length. Mine was a little longer than the 458 Lott. From the base to the belt is 2.500 and overall length is 2.900. My barrel is marked 450-5000 Express.

30-06... Your welcome