I have the .338x74R reamer, (Keith) but i never chambered one up. I instead came up with a some what bigger capacity case, and did make up a combo bbl. chambered for it,
You can see it in the pict, second from the right, next to a 30-06. Actually, left to right is, 416, 375, 338 and 30-06.
I also made up a 9.3x74R imp... You can see it here next to a factory 9.3x74R,
These would be perfect for a Ruger number one!
Anyway, i did all of this long ago, and i no longer do any work like this, but i thought you may be interested in seeing them.
DM