The case length is kind of the key here and I can't tell for sure just looking at the casting where the neck ends and free bore begins and neither could the two gunsmiths I work with. It could very easily match the dimensions you've posted above but I don't know how to tell.
The 400 Express is a necked down 450 so that isn't it. I can find virtually no information on the 10x60R.

In rummaging around thru loose cartridges I found this dead example that's a perfect fit at the base.
However it military marked and I don't know the caliber. I'm wondering if it could be trimmed and blown out(fire formed) for reloading once identified?

Last edited by italiansxs; 06/21/11 06:04 PM.

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