Anyone tried this combo? I'm assembling the parts to register a SBR, and wanted to hear people's thoughts.

Any stripped AR 15 lower should work. It takes a SIG MCX stock adapter and an MCX lower parts kit which are both available on SIG's web site.

Bill

That's what I thought as well, but I talked to a guy yesterday who said Aero Precision lowers were finicky with other companies' uppers. I hadn't heard that, and am skeptical, so I thought I'd reach out and see if others had tried this combo.

If the lower is finicky, I'm fine going with an Aero upper, but it seems their method of adjusting the gas, which requires an Allen wrench, is a little awkward. But the lower is excellent quality.

This message has been edited. Last edited by: AUTiger89,

MCX upper require an adapter to fit on any AR lower. Brand or quality isn’t an issue, they are designed differently.

The only things that are different with an MCX lower are that the recoil bumper is integral and the MCX uses 6061 billet aluminum. If memory serves, the Aero lower uses 7075 aluminum forgings.

The 7075 is stronger, but corrodes a bit more easily than 6061 aluminum. The two parts that the SIG MCX lower parts kit does not contain are the right side magazine release button to fit a standard lower and the closure for the trigger guard.

The MCX upper has a firing pin safety on the bolt carrier. Hence the fire control group's hammer must be able to move the safety out of the way with enough force to fire the round.

SIG offers the Match Lite Duo two stage trigger to get the job done.

I don't recommend the Aero upper. The SIG barrel and bolt carrier are designed to work with the SIG upper only. I've never heard of an MCX with any upper other than SIG. SIG's stripped uppers are expensive, but they work.

Bill

I'm looking at an MCX upper with an Aero lower. I have the adapter kit to make the MCX upper work with normal AR lowers.

If that combination doesn't work, I'll pair an Aero upper with the Aero lower.