I had a pre 64 (mid 50s make) rebarreled and new magazine box. I have not fired it yet. Should there be any concerns?

I assume you had the bolt face opened up to accommodate the magnum size case head?
If that is done what more could be a problem?
I would assume who ever did the work also test fired it.
There is a lot missing from your story...

Yeah, like feeding, bolt stop, rail work, and ramp work! This could be the beginning of another Bubba the Gunsmith story.

Waiting.....

they made them in 300H&H at the factory.[shrug]

And the problem would be??? Packy

quote:

Originally posted by Lamar:
they made them in 300H&H at the factory.[shrug]

But the OP says it was an 06 and a new barrel in 300 H&H was put on with a new mag box.

A few hours at the range will address all your questions..Its not a big deal to modify a 06 to a 300 H&H, Ive done it several times. a modified or new bolt stop, open the bolt face, tweek the feed rails perhaps, but you added new bottom metal so that's probably done. You might make a cut out in the rear of the action to clear the long case or loaded round. and perhaps a slot ala pre war, in the rear of the front ring to assist in loading..I think I covered it all, its been awhile..I sure like the caliber..