I was shooting the other day with my wife and father-in-law.  I had 11 mags.  1 was Orlite and the others are all USGI.  We shot for a while with the USGI mags, no prob.  My father-in-law picked up the gun and began to fire.  Fired numerous rounds with the orlite, no problem.  Fired about 7 in rapid fire style, semi-auto, and no probs.  He fired 2 more rounds no prob.  The last round in the mag, blew the mag apart completely and burned his forearm.  Not sure what happened, but I have heard about problems with Orlite and I will only use USGI mags now.  My lesson was learned.  

Jake;
The problem your father-in-law had isn't a magazine problem. Someone else more knowledgable will provide additional information, but a magazine won't cause the type problem you described.

My 'guess' is you had a head separation of the round, a slam-fire, a double charged load, or something of that nature, and it just so happened to occur when loaded from the orlite.

What type ammo? What did the brass look like? Any damage to the bolt/carrier/firing pin?

Pardon me. That doesn't make sense. If firing the last round in the mag blew the mag apart and burned his arm, I can only assume that the shell casing leaked gas back into the action from a split case head? blown primer?

What do you think would have happened if an aluminum mag was in the rifle.  Pieces of metal in his arm?

I don't own any stock in Orlite, or any other mag manufacturer, so it's OK with me whatever mags you use. It just seems a little strange to blame the mag for an ammo failure; unless I misunderstood what you were relating. I just don't see how you can get burns on your arm from anything but an ammo failure, or premature unlocking of the action.

What They said...  Honest truth...