Confirmed: Sig Sauer MPX will accept AR-15 Drop in triggers

So, as of 5/17/2015, I had yet to verify that the Sig Sauer MPX could actually take any AR-15 drop in trigger. Well, a buddy of mine just happens to have an MPX, and this is what he sent me this morning:


What you are looking at is an MPX lower receiver with the stock trigger removed (which actually maxed out his trigger gauge) and a CMC 3.5lb flat-face drop-in AR-15 Trigger installed. What is interesting to note is the setup of the whole system. Both the safety and rear take down detent springs are held in by the grip, which makes the whole process fairly simple. Removing the ambi safety involved driving a roll pin out (as seen in the picture on the right) and the right side safety lever comes off; then the whole safety can be removed like normal. My buddy does like the flat-face trigger on that CMC. I’m not much of a fan for the looks of it, but they apparently are superior to curved trigger faces. I beg to differ.

I suppose it’s official then; Sig wasn’t lying when they said it took a standard AR-15 Trigger group. I’ll post more pictures after I shoot the gun.

Now, if we can only find some magazines…


UPDATE: I finally got to handle the gun with the new trigger… My reaction:

Gives me a Chubby

I will admit, the trigger is nice now. Moreover, the flat-face trigger isn’t so bad on the hands after all. I still think it’s ugly, but it works well. It has a fairly crisp single stage release, but it seems to have a bit more overtravel in this gun than in standard AR-15s. It’s still an improvement by leaps and bounds, nonetheless. I highly recommend a new trigger for everyone who intends to buy an MPX.



Sig Sauer has apparently announced that changing the fire control group (well specifically removing the bridge from the fire control group) will void the warranty of the gun. More info here:

I think my buddy will stick with the CMC trigger, however, because he’d rather risk breaking the CMC than putting that shitty factory trigger back in the gun. The worst thing that can happen to the gun is the trigger might break or wear out prematurely. The bridge appears to just keep the disconnector from traveling too far while the trigger is pulled and seems to act as an overtravel stop for the hammer itself. That brings up the question: If you have a pre-calibrated trigger with a fairly low mass hammer (much like the CMC and other single piece trigger assemblies), does it need that bridge? I’ve put 200 rounds so far through the MPX with the CMC trigger in it now, and there were no stoppages and there doesn’t appear to be any excessive or unusual wear on the hammer so far. If someone is willing to donate a few thousand rounds of 9mm luger to me, I will happily torture test the CMC trigger for the good of mankind to find out if it will break!



 Over 1000 rounds of various 9mm (hot stuff and standard pressure) with no excessive wear, damage, cracking, or anything. The CMC trigger belongs in this gun and is a must buy.


6 thoughts on “Confirmed: Sig Sauer MPX will accept AR-15 Drop in triggers

  1. In my mpx booklet on my new gen 1 mpx I bought in April 2016. Sig says they will except the change of triggers without voiding warranty. Any other changes will void it.


    1. When my buddy got his last year, it didn’t actually mention anything about triggers in the user manual. The notice that it would void the warranty came out after the MPX was released, so they might have had a change of heart since then. This is good news!


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