You should let me get a mess of brass and link jammed up in it and beat it shut with multiple hammer fist strikes and tons of profanity. It would be the most authentic test for both of us. We're they originally aluminum? I've beat the shit out of them, and seen everyone else do it too.
They've always been AL near as I can tell. Most have so much rattle can paint stuck to them that it's hard to tell.
As for how they run... (bolts, carriers, extractors...)
The learning curve has been interesting to say the least. As I have mentioned, I don't get prints or models with this stuff. A part shows up, and the party starts from there. Once I have the first article and send it off to the client, the phone begins to ring.
"Hey, it's missing this chamfer. . ." - "The part you sent me doesn't have it."
From there, we take a forensic look at the entire inventory and realize they are all basically "cousins." -probably the kissing kind. Lol. -just different enough to make things interesting. It largely boils down to who was making what at a given time.
A lot of contract stuff works like this, unfortunately. Things evolve, and when they migrate to the next low bidder, the tribal knowledge and natural evolution get stopped dead in its tracks. What it's done is start to provide me with a comprehensive view of this system's natural migration/evolution. We're now attempting to take the best features from the legacy items and consolidate them. It's a big job but very rewarding as it forces me to nitpick at the documentation on my end. Tool selection, material conditions, and ensuring that what I'm making actually follows the original intent and doesn't end up as something with my "spin" on it.
