Below is a comparision of the wall thickness of the Colt/Surplus Ammo & Arms/Rock River/Aero recievers. References of left and right are of the reciever with the front facing away from you. I was curious of the wall thickness due to the fact that I had read the Surplus Ammo and Arms recievers were lighter than others.  From visual inspection, It appeared that one reciever might be thinner than the other, but on second inspection, I noticed there were bevels on one of the recievers that made it appear thinner.

Colt (6450 9MM)               Left .095         Right .098
RRA                                  Left .095         Right .095
Aero                                 Left .102         Right .087
SA&A                               Left .098         Right .089

Left to Right   Aero, Surplus Ammo & Arms, Rock River    Colt is not in the picture (it was not a stripped reciever)

I have 2 RRA lowers and they're different.

Did you weigh the 3 lowers there and see how they compare?  There is a lot of different places to remove "weight"/material on a lower.

The front of the mag well, the inside the trigger area, the back under the receiver extension threads, and two of those lowers have the sear block area in them.

Ill take the Colt lower ...oh its not the EEjust joking thanks for the measurements its good to see between the manufacturers tolerances on machining..anyone no what the spec is in the TDP for comparison im sure Colts would be the closest to that just curious what the +s and -s are on the TDP for thickness?

Haven't weighed them, don't have a scale that is precise enough.. The SA&A does feel lighter though. I was originally concerned with the wall thickness and durability of the pin holes. I just measured a Colt M4. The other Colt I measured earlier was a AR 15 6940 (9MM). This is a select fire M4 RO933.

Colt             Left .095                 Right .099

high shelf vs low shelf

eta: nvm, wouldnt correlate with your findings

The SSA is made by Aero, so really it just shows that there is variation between lowers of the same make.

Also lots of companies might get lowers from different manufacturers.

Topic Moved

That is cute, but it doesn't really mean or prove anything.

My interest is in the fact that a thicker side wall would give more support for the hammer and trigger pins. I've noticed that there appears to have more wear at these points when we use cans or on the 9mm fa lowers. Not trying to prove anything, just a FYI on the walls of the recievers.