looking for 9MM AR vs Sig MPX observations

[nate89]

I have built 2 9mm ARs. I also see quite a few of them at the local USPSA matches. I initially went with the glock lower, but have since changed to a QC10 colt lower. I had a load of problems with a palmetto 9mm AR (surprise!), and got rid of that after sending it back to them and still having the same problems. I then build a QC10 gun (QC upper, bolt, barrel, and lower) that runs like a champ, no issues at all. I am using a Vltor A5H4 buffer with an A2 spring in a carbine tube and it is about the perfect length for engaging the bolt catch without battering it unnecessarily. I then did a QC10 colt lower, JP bolt, Colt SMG upper, and Faxon barrel. Same result, no issues.

I also have a friend with an SBR'ed MPX with the Sandman Wolf suppressor. We shot that last weekend after a USPSA match with the Fiocci 158 grain subs and it was incredibly quiet. My 8.5" with my Omega 9k is not as quiet, but will comfortable to shoot indoors without ears.

I think the MPX is a pretty great option if you are looking for a 9mm rifle, and after you buy the higher-quality parts to put a 9mm AR together, the cost isn't as different as you might think. Plus I am seeing MPX mags coming down in price, as well as the availability of aftermarket triggers/charging handles/etc.

TL;DR: After building and buying a few 9mm ARs, if I had to do it again I would probably just buy the MPX and be done with it. One aftermarket part my friend said was almost required when suppressing the MPX was a new gas insert that eliminated gas to the face. I can't remember the make/model, but it wasn't very expensive and took all of 1-2 minutes to install.

I still find the only really use of a 9mm rifle is for fun, or for shooting PCC division in USPSA, or as a training gun that you can use on occasion instead of a real rifle. You can shoot steel closer, ammo is a bit cheaper, etc.

[indianalex01]

I politely disagree with you. I do agree with you on the 300 useless... that was a good one.

[ccosby]

I've shot 9mm ar's before as well as mp5's, the beretta cx4, and a few others. I've only played with the scorpion and wasn't impressed. It is cheap, I'll give it that but I'd rather spend a bit extra and get something I think it nicer. I really like the sig. Threw a larue trigger in it(Mr. Larue said on TOS he would warranty them early on) to get rid of the guns biggest issue which was the crap trigger. I went a little overboard on my gen 2 sig past that.



Had TSC machine cut the barrel to 5 inches and install a 3lug over it. He then refinished the gun in the burnt bronze and filled in some of the engraving(I didn't want it all filled in with black). They had the idea to leave the top rail black which I think worked well. I have the next level armament charging handle since that was the first with the lifter to stop the handle from scraping the back of the gun(a problem sig should fix). Running an octane 9(now with the shorter 3lug vs that picture), trijicon mro, bcm front grip, etc.

I don't think I've had the gun jam yet. It eats everything I've thrown at it. I will say I've found that some ammo is really gassy while other isn't. I mostly shoot 147's through mine. I haven't messed with the gas system on it, since it runs everything I don't want to mess with it. For what it is worth I've had the same issues with some ammo on my mac 10 and on full auto gassy ammo sucks.

Now the MPX is really coming into its own. Multiple charging handle options, aftermarket rails(which swap in seconds), more trigger options, aftermarket barrels(since sig sucks and hasn't supplied them like they should), etc.

[usmcvet]

I've shot 9mm ar's before as well as mp5's, the beretta cx4, and a few others. I've only played with the scorpion and wasn't impressed. It is cheap, I'll give it that but I'd rather spend a bit extra and get something I think it nicer. I really like the sig. Threw a larue trigger in it(Mr. Larue said on TOS he would warranty them early on) to get rid of the guns biggest issue which was the crap trigger. I went a little overboard on my gen 2 sig past that.



Had TSC machine cut the barrel to 5 inches and install a 3lug over it. He then refinished the gun in the burnt bronze and filled in some of the engraving(I didn't want it all filled in with black). They had the idea to leave the top rail black which I think worked well. I have the next level armament charging handle since that was the first with the lifter to stop the handle from scraping the back of the gun(a problem sig should fix). Running an octane 9(now with the shorter 3lug vs that picture), trijicon mro, bcm front grip, etc.

I don't think I've had the gun jam yet. It eats everything I've thrown at it. I will say I've found that some ammo is really gassy while other isn't. I mostly shoot 147's through mine. I haven't messed with the gas system on it, since it runs everything I don't want to mess with it. For what it is worth I've had the same issues with some ammo on my mac 10 and on full auto gassy ammo sucks.

Now the MPX is really coming into its own. Multiple charging handle options, aftermarket rails(which swap in seconds), more trigger options, aftermarket barrels(since sig sucks and hasn't supplied them like they should), etc.

I just ordered the new shorter three lug adapter from silencerco. It looks much smaller. What's the difference in length? I shot a KRISS VECTOR yesterday! Damn It now I want one.




Sent from my iPhone using Tapatalk

[ccosby]

The new one is almost flush, it's over an inch shorter.

For the kriss vector I've only shot them in rifle config and they are interesting. Charging handle sucks but other than that the are kinda cool. I actually bought a factory sbr in 10mm, paperwork went out like 6 months ago. Sadly I have a feeling it has another 3 or 4 left(still waiting on stuff that went out early January). I just wish they would get off their asses and make the extensions for the glock 20 mags.

[usmcvet]

The new one is almost flush, it's over an inch shorter.

For the kriss vector I've only shot them in rifle config and they are interesting. Charging handle sucks but other than that the are kinda cool. I actually bought a factory sbr in 10mm, paperwork went out like 6 months ago. Sadly I have a feeling it has another 3 or 4 left(still waiting on stuff that went out early January). I just wish they would get off their asses and make the extensions for the glock 20 mags.

I'm looking forward to the shorter 3 lug. The CH is strange. On the KRISS. A VFG is something I'd need to prevent malfunctions. None of us was able to charge the last weapon with 100% reliability. We would often have an empty chamber and failure to fire.


Sent from my iPhone using Tapatalk