I recently purchased a very nice 6.9M hand stamped Inland, with a 2-45 Inland barrel. The gun is correct throughout. Since at the time of production, Inland had both a M1 & M2 production contract, and any given barrel or receiver could end up being an M2, were the late production Inland receivers and barrels manufactured more robust to handle the effects of sustained full auto fire?
I realize that many carbine components were improved/updated during production, such as slides, extractors, ejectors, flat to round bolts, etc., but I don't recall ever reading whether there were any improvements in the metallurgy or upgrades of the barrel or receiver. Seems like the little carbine would take a beating in M2 form, when utilized in combat.