Different M10 Upper Receiver Lock?

[Jack007]

Going through boxes of MAC stuff the other day I ran across this M10 barreled upper with a 9mm bbl. Wondered if anyone had seen one like this?
Maybe this was a one off done by someone as a repair? The cotter pin idea is definitely easier than driving out the long roll pin. Given the lack of relief for reinforcement tabs I suspect this is not later RPB, but you never know with this stuff. The finish is definitely older salty parked and not blued, and it was done after everything was milled and drilled. Note the electropencil number 1448 on the weld plate. There's also a letter F stamped on the front of the block just below the barrel. That seems much more of an earlier MAC thing.

 

[timkel]

The lever latch and F stamp says Powder Springs upper to me. The rest is owner operator mods.

 

[SecondAmend]

There were a few SOTs who put together Ingram pattern subguns from parts, and there were also some individuals who made Form 1 Ingram pattern subguns from parts. IIRC, Shotgun News had ads for all the parts one would need, but that was about 40 years ago so I can't be too sure.

IMHO, YMMV, etc.

 

[MitchWerbellsGhost87]

Looks like an aftermarket modification, or someone else built the upper with parts from the MAC auction, receiver shell and a front trunnion. What kind of barrel is in it? That can be a huge indicator as to who built it and when… it’s not usually necessary to remove the front takedown latch, so this seems like it was done out of necessity when first installing the latch, it may have been built from parts and this is just how they ended up having to do it. I should add, RPB did use the receivers with no tabs, there were a bunch of early open bolt SAPs that used the Marietta M10 upper (large front trunnion for no tabs, no latch). I think they switched over to the receiver tabs at some point in 79-80. they were using up leftover Marietta M10 uppers/trunnions, eventually they started using the Marietta M10A1 uppers and incorporated the receiver tabs into the SAPs. That said, this one clearly has the latch, which is a feature that was not used by RPB on the guns they built up from MAC parts. The latch is exclusively powder springs MAC.