Mr H
Banana'd
I'm not sure that is how a gun part is defined. I can mail many items from an AR to folks except the lower receiver - bbl, flash hider, upper, etc., and those are gun parts.
While true, you need to consider the Federal definition of "firearm".
The magazine is not covered under that definition, which makes the mag no different than a dust cover... This alone makes Cabela's policy problematic.
But, I don't see them setting up inventory channels just for MD, NY, CT, CA......