I have 2 of these suckers that I acquired, circa 1995.  One fits decently in my Anderson lower, one not so well.  It can be forced and is obviously one of the rejects that got mixed in with the good.  As it is, it looks like it's just out of tolerance.  I'm thinking about trying to sand it down to make it fit, as a last resort magazine.  I was wondering if anyone else tried to rehab a reject Cooper or just cannibalize it for parts.

During the ban years it might have been worth a level of effort to try and rehab that mag, but that is not the case anymore. Gut it for spare parts and chuck the body in the trash/recycle bin.

This +1

A questionable magazine will f'k you when you need it the most. Cut your losses, or at least mark these mags with a big X so they are never expected to be depended on. Way back, I'd keep a problematic mag for range use- then during qualifications one screwed me.

Mags can be had cheap- they should be quality from the start.

Or sell to someone in MA

That's dirty, yo.  Those guys may need them not too far from now.  I guess I'll just use the body in a prop Star Wars gun I was looking to build.