Form 1 Sig MPX

[Madcap_Magician]

Damn! That's fast!! Hope they get the Form 4 eForms up and running soon. I just sent the Form 4 paperwork (trust) in for a friend's factory DD SBR, and his suppressor shows up tomorrow so another Form 4 will be going out this week. He's probably looking at 8 months.

Yeah, that's why I bought the pistol and went with the Form 1 path instead of just buying a factory SBR and transferring by Form 4. I'm hoping that e-File Form 4 is active by the time I have the money to buy the shorter barrel and a suppressor.

 

[Madcap_Magician]

my cousin has a SBR mpx with a 4.5" barrel and a can. It is GASSY. we shot it next to my cmmg guard upper I built, and the guard was more pleasant. The 4.5" barrel was also not accurate for us at 50yds. It was missing the 8" gong about half the time, while we were pinging away with the 16" scorpion carbine and the 8" guard. The scorpion was the least gassy, but had the most recoil. The mpx and the guard were a tossup as far as recoil went.

There was a thread over on ar15.com that referenced the owner of bowers suppressors talking about the 5" vs 8" guard, and he said the 8" suppressed better. But I was unable to find the scource of that comment, or the context that went with it.

All 3 guns were better than a blowback ar9 in terms of recoil, gas, and suppression.

I have only shot a 9mm Colt SMG and the MPX, but the Colt had an oddly sharp and unpleasant recoil impulse to me. It wasn't powerful recoil... but it was kind of a sharp, swift jab to the shoulder, if that makes sense. A better recoil pad than the base M4 stock would probably have helped.

But the MPX has basically zero recoil to me. It's like shooting a rimfire rifle and easier than shooting a 5.56mm M4, which is of course itself practically recoilless.

I've heard a lot about the Scorpion being the best for suppression, but I may never get around to suppressing my MPX, so I'm OK with it the way it is with the better shootability getting the nod for me over potentially better and less gassy sound suppression in the future.

 

[Gtscotty]

It is GASSY. we shot it next to my cmmg guard upper I built, and the guard was more pleasant.

Did you buy the barrel and BCG kit? I've really been wanting one of their delayed blowback setups for a suppressor host, but assumed they didn't sell the special bolts and barrels separate. I didn't think to look on their site until I read your post, now I need one.

How does yours work?

 

[greyling22]

I did. 8" kit from opticsplanet. https://www.opticsplanet.com/cmmg-inc-mkg-guard-9mm-barrel-and-bolt-carrier-group-kit.html it was roughly 350 after the 10% off code. though I see they are now OOS.

I added a cheap ebay handguard and I'm running it on an sbr lower using the endomags from mean arms. https://www.meanarms.com/products/detail/endomag-9mm
it works great. I did have to modify the endomags to fit the guard bolt since I bought them from aimsurplus, along with my upper https://aimsurplus.com/anderson-manufacturing-lightweight-sport-ar-upper-receiver again, now OOS, and if you decide to go that route, I have some pictures posted here https://imgur.com/a/1M8rsJE and as far as I can tell, those are the only pictures on the internet showing you how to mod your endomags.