Hi there,
I have just seen this thread and would like to reinforce the desire to see photos of the frame without the stock sides. THere are several things which look wrong about this so far.
1. We do not normally stamp part numbers on to the magazine and the number which is stamped, 4746 is not a magazine part number, it is for the base only. That aside the magazine does look like a .338 CIP.
2. The frame looks old and looks like it is a short action and not a long action, but a .338 magazine would not fit length wise into a short action magwell.
3. It could be that there is a welded section added to the magwell sides in order to lengthen it for a .338.
4. There is a weld forward of the magazine section which suggests this is a very old welded frame or one that has been modified.
Remove the stock sides, take some pictures and I think all will be revealed.
When did you buy it and who did you buy it from?
Tom Irwin
Accuracy International