To mpx or not?

[Shooter212]

I was looking at building another Ar type pcc, but I found a decent deal on a used mpx. I have always kinda wanted one just a little leery have seen some not run. Just wondering if anyone has gone from Ar type to mpx and thought it was the greatest thing and wouldn’t go back. Or has anyone gone from mpx to Ar type and thought not dealing with that anymore. Are mags an issue getting them to work with extensions.   

[Underwood]

i went from AR9 to MPX.. afterwards i sold both AR9's .  If you clean it, it wont let ya down.

I have installed the TF and TT basepads and have never had a problem. After i let my friends shoot the MPX several of them went and bought there own.. 

 Its the softest shooting 9mm carbine you can buy. 

Edited September 17, 2018 by Underwood
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[Shooter116]

I have shot my Gen1 MPX in competitions for three years without it ever letting me down. You do have to clean them well before every match but they are very reliable. It’s short (mine is an SBR) and lightish so very fast on bay stages. 

[Smithcity]

Guys at the club and I have experience with several gen 2 mpx's, both title I and title II. Probably a combined 24k rounds through 5 guns. Only one has been reliable, various different problems with them, have had to send items back to sig.

 

If I was doing it again, I would just get a JP. If you reload, you can tune the AR9 tk be just as soft shooting as an MPX, it will be more reliable. Had another catastrophic jam the other week in a match, couldn't clear it, zeroed the stage. Infuriating. 

[Underwood]

 

28 minutes ago, Smithcity said:

Guys at the club and I have experience with several gen 2 mpx's, both title I and title II. Probably a combined 24k rounds through 5 guns. Only one has been reliable, various different problems with them, have had to send items back to sig.

 

If I was doing it again, I would just get a JP. If you reload, you can tune the AR9 tk be just as soft shooting as an MPX, it will be more reliable. Had another catastrophic jam the other week in a match, couldn't clear it, zeroed the stage. Infuriating. 

The problems i have seen with others is when they load their ammo too long. The Sig likes them short..... Are yall using reloads in the 5 MPX you are talking about ? 

I agree you can hand load low PF ammo to make an AR9 recoil like a MPX does with full power stuff.

 For steel challenge i load 115 grain Blue Bullets with 3.2 titegroup  1.10 OAL.... shoots like a .22

 

[fbzero]

In my experience, the MPX shoots lighter, and seems reliable *if you keep it clean* based on my buddy who has one.  My CK Arms AR-type PCC is lighter even though it doesn't shoot as light and seems to be reliable no matter how dirty I let it get.  My wife and I shared it at the Lucas Oil PCC match, and with both of us shooting all 12 stages, never had a single failure or malfunction of any kind.  We also shot Friday when it was pouring rain for over half of the time.  That certainly wasn't the norm in our squad.

IMHO, it's a trade-off and you need to choose which attributes are the most ideal to you.  Whether 3gun or USPSA, I have at tendency to not clean match firearms very often, so the level of reliability that mine offers without having to worry about cleaning it before a match comes in pretty handy.

Edited September 18, 2018 by fbzero

[Smithcity]

4 hours ago, Underwood said:

 

The problems i have seen with others is when they load their ammo too long. The Sig likes them short..... Are yall using reloads in the 5 MPX you are talking about ? 

I agree you can hand load low PF ammo to make an AR9 recoil like a MPX does with full power stuff.

 For steel challenge i load 115 grain Blue Bullets with 3.2 titegroup  1.10 OAL.... shoots like a .22

 

Oh yes, used all sorts of factory ammo and reloads, bullet shapes and lengths. It likes a slower burning powder, it can feed 1.13" oak just fine, one of them will not feed HPs well at all. They seem to do better when hotter ammo. 

[GregJ]

I have a Gen2 MPX carbine that has been solid with same reloads I use for CO.  124gr Zero RN @ 1.100.   From what I have read, those that have issues with the MPX has mostly been due to the gas port size. Seems the later Gen2s like to be a little over gassed due to a smaller gas port than earlier Gen1, though mine has not had that issue.  In Lead We Trust has a lot of spare parts for the MPX, and will also enlarge the gas port for a very reasonable fee. 

 

The 30rnd mags work best with stock springs and Springer +10 base pad, or the enhanced power spring with the +10 and the extenion, giving 47 rounds.  This has been very reliable.  

 

The MPX likes to be run wet, but not the gas piston or tappet - put them back together dry. 

 

I have only shot a few rounds through a JP once, but the recoil was significantly more noticeable.  But it is much lighter I believe. 

[Underwood]

We took two gen2 sig mpx to Lucas oil pcc match.  Both shot 12 stages some of it while raining . 

Zero malfunctions . Both are stock with upgraded hyperfire triggers 

 

[TeedOff]

Happy enough with mine that I sold off an AR9 so I could get a backup MPX just in case.  I shoot 147 gr Blue Bullets primarily thru it, some plated reloads.  I let it get dirty as hell and it still runs.  Hiperfire or other upgraded trigger is a must.  I've added on a few other bits to make it to my liking...Isler carbon fiber hand guard and a std AR15 buffer tube and stock are the most important changes to me.  Mine has ran great thru the JP PCC match in the spring, in one level 2 (Iowa sectional) and 15 level 1 matches this year. 

 

As far as mags go I have everything from 20 round mags to a 58 round Taccom splice setup.  I've had no problems with Gen 2 mags in my Gen 2 gun, however I've been a bit leery about using the Gen 1 mags in a match.  They always seem to work fine in practice but I've not been willing to take that leap in a match.  I use both Taylor Freelance and Springer Precision 10 round extensions and also have a couple of the Springer 10 round extensions that built up to a 47 round mag.  Works great.  I find my classifier mandatory reloads seem way slicker with the MPX compared to any of the Glock based AR9's I had.

[Shooter212]

You guys are not making this a cut and dry decision. The reliability issues scare me I have never had issues with my ar types they just run. I feel like I can split pretty fast with the ar types so I don’t know if I’ll gain anything there. Spending a bunch of extra money to lighten them up sucks too. But they still look so cool when people shoot them and they just don’t move. 

[Smithcity]

4 hours ago, Shooter212 said:

You guys are not making this a cut and dry decision. The reliability issues scare me I have never had issues with my ar types they just run. I feel like I can split pretty fast with the ar types so I don’t know if I’ll gain anything there. Spending a bunch of extra money to lighten them up sucks too. But they still look so cool when people shoot them and they just don’t move. 

There are less things that can go wrong with a blow back AR9 than say a short stroke gas piston. If you go the AR9 route, you need to watch out for the upper, lower, and chamber, i.e. the angle / depth that the magazine is presented to the chamber is critical. Many franken-build AR9's are hit or miss when it comes to feeding. If you go that route, you might consider an upper, lower, and barrel from the same manufacturer. 

 

I have two gen 2 Sig MPX's, when they run, they are a blast. They get dirty quick, and probability of malfunctions go up past 300-500 rounds. As others mentioned, the gun likes to run wet, NEVER oil the gas system (tappet / plug). Seriously, if you are reloading, you can tune an AR9 to be equal to the MPX in recoil. I've done it myself. If you go the MPX route, I do recommend opening your gas port to 0.065", gives you the ability to more reliably run ~130PF ammo.

Edited September 19, 2018 by Smithcity

[rowdyb]

shot a friends gmr 13 and 15. shot a friends psa gun. my only experience with glock mag guns. left me just going "eh ok".

 

i've owned three 9mm, colt mag guns. two dedicated and one with a mag block. cmmg and rock river armory between all three.

 

i now have a mpx and no colt mag guns. love the mpx. butttt..... full disclosure i had to do stuff to it and get it to work with my load.

[troupe]

I had both. I miss my Sig. I sold it because of college money. My AR is flawless, but the Sig was much better.  I think the problems that you see about Sigs are from people pushing the limits to gain every advantage, which makes sense because it is racing. The Sigs were designed for factory ammo. Folks are running mouse fart loads, running the guns to dry. Keep it lubed and run ammo that is hot enough and it will be flawless. Mine shot factory Federal American 115 so soft that when I got it, I moved up in places in matches just because of the confidence that I had on hard or longer shots.  It is that soft of a shooter. I only wish that Sig had better customer service for the shooters that help support them. I know that Sig is so big, that a few competition shooters does not mean a lot. I am looking forward to the new MPX "competition" that has been shown at the shot show.

[Chillywig]

I have a gen 2 carbine that has always ran factory wolf steel cased ammo 100%. I did put a Hyperfire trigger in it, changed the hand guard to an Isler, replaced the charging handle, added a mag well, replace the collapsible wire stock with a minimalist, and ceracoked it white. Now granted it ran fine before changing all this stuff but I like to tinker. It never did like my low PF reloads. Once I tried the wolf and it ate it up I decided that was all I was going to feed it. 

 

Couple side notes. I also have a gen 2 pistol with a brace. It is set up basically the same way minus the cerakote job. When pulling the charging handle on the pistol next to the cerakoted carbine the pistol feels like junk. It just feels gritty and takes almost twice the force to rack it. The cerakote made the carbine so slick when I first got it back I shot a match with out lubing it. The the inside of the receiver was dry - 0 lube. I had cleaned the bolt and carrier while the gun was getting painted and it was only lightly oiled.

[Underwood]

18 hours ago, Chillywig said:

I have a gen 2 carbine that has always ran factory wolf steel cased ammo 100%. I did put a Hyperfire trigger in it, changed the hand guard to an Isler, replaced the charging handle, added a mag well, replace the collapsible wire stock with a minimalist, and ceracoked it white. Now granted it ran fine before changing all this stuff but I like to tinker. It never did like my low PF reloads. Once I tried the wolf and it ate it up I decided that was all I was going to feed it. 

 

Couple side notes. I also have a gen 2 pistol with a brace. It is set up basically the same way minus the cerakote job. When pulling the charging handle on the pistol next to the cerakoted carbine the pistol feels like junk. It just feels gritty and takes almost twice the force to rack it. The cerakote made the carbine so slick when I first got it back I shot a match with out lubing it. The the inside of the receiver was dry - 0 lube. I had cleaned the bolt and carrier while the gun was getting painted and it was only lightly oiled.

I agree i found that Blazer 155 runs perfect and groups good at 100 yards.. its my go to white box ammo.. 

I also dislike the factory sig hand guard very much.  I had the rail milled off the top so i can get a better grip for now... But I have a Taccom carbon fiber one on the way that we are gonna install on the factory barrel.. Ill be sure and post some installed pics when finished.

 

[v1911]

After 400+ rounds of WWB through my MPX, it has run flawlessly. Not even a single hiccup. I lube it before each match but I've yet to clean it. It's heavily modified, but the barrel, gas port and internals are still factory.

[hgr2]

My Mpx has been great, replaced the collapsible stock and installed a Timney MPX trigger. Runs great with 140+ PF ammo. I'm not a gamer so I shoot the same ammo I would carry. Really accurate too.

[chase214]

What is the diff from gen1 and gen 2

[Chillywig]

hand guard, gas port size, and mags don't interchange easy so I assume there's some internal stuff too

[Gregg K]

I spent a bunch of money on my AR9 changing and experimenting with different buffers, weights and springs and finally thought it felt pretty good and ran flat. Then I got an MPX and the difference is amazing. When I shoot one on a day and then the other another day it's hard to compare but when I take them both out and run them side by side there is no contest, my MPX is softer and flatter shooting. I have had no issues running a range of different power factor rounds. I have run about 2500 133PF rounds through the MPX without a malfunction. At this point I would dump the AR in a second except I have too much tied up in it. The MPX ran right out of the box, that has value right there. I did dump the crappy factory trigger and installed an Eclipse. I'm waiting to see if any of the terrible stories about the Hyperfire trigger failing come true but so far so good but I'm still pretty low mileage on it with just 2500 rounds so I'll have to wait and see how it holds up. I have cleaned the MPX twice just to check it out but nothing to note. I guess I should run it till it starts to fail just to see how long you can go in between cleanings. I think everyone has to figure out their own cleaning schedule since the cleanliness of your ammunition is a big factor.

[chase214]

I want to get into pcc just unsure if I should go mpx or build ar 

[rowdyb]

I know it's idpa, but here is me shooting mine just so you can see it in action

 

[Acer2428]

IMO Just buy the MPX. I'm on like my 5th itteration of AR9. From Colt mags, to Colt mags + ULW barrel to Glock Mags to Glock mags + guard, etc.

 

My advice at this point is either buy an MPX or a Guard whole and call it good, with the edge going to MPX. The mags are absolutely fantastic. 

[NumberTwo]

MPX