Sig MPX?

[fatdog]

If you are a serious competitor, I think you want three MPX guns, so can practice with one, compete with another and have a third for back up or parts.

Reminds me of the CAS mantra on Win'97's and their reputation for breaking, if you run one of those you need three, one to start the match, one to finish the match, and one that is already away being fixed.

I have been tempted about getting one of these, but this whole report is not encouraging. I have enough stuff that breaks routinely. All evidence including your experience and the competitors who excel with it says it is one of the best shooting of the PCC platforms.

[JSGlock34]

All sorts of things around the firing pin, firing pin string, extractor and gas system. I am not even counting triggers which are tough in the MPX and blow back AR9 guns.

Thanks - that's interesting. Is it something particular to the design or 9mm gas system that's causing these problems? It doesn't seem like the MCX suffers from the same issues (not an apples to apples comparison but some shared design history).

[GJM]

Thanks - that's interesting. Is it something particular to the design or 9mm gas system that's causing these problems? It doesn't seem like the MCX suffers from the same issues (not an apples to apples comparison but some shared design history).

I asked the exact same question and was told that the MCX does not have a gas system issue because the rifle powder burns so clean, and the MPX has gas system issues because the pistol cartridges are quite dirty.

[HCM]

Sunday @JM Campbell and I got to shoot on a friends property and I took the opportunity to try a variety of loads in my 8' gen2 MPX before detail stripping and cleaning the gas piston. Each was a 25 round magazine:


1) Blazer 115 grain FMJ - multiple malfunctions
2) Speer Gold Dot 124 grain +P - No malfunctions
3) Speer Lawman 115 Grain +P FMJ - No malfunctions
4) Federal Synthtech 150 grain Coated Truncated Cone - Multiple malfunctions
5) Winchester Ranger 147 grain bonded JHP - Multiple malfunctions
6) Federal American Eagle 124 grain FMJ - No malfunctions
7) Federal White box (LE Contract) 147 grain TMJ (truncated cone) No malfunctions
8) Magtech 115 grain FMJ - No malfunctions

It seemed the hotter the ammo the better it ran and it seemed to work best with the +P stuff.

Anyone else had similar experiences with their MPX ?

I've got a few thousand rounds on the gun (Mostly Magtech 115) so I'll try and repeat this after cleaning the gas piston and compare results.

@Clusterfrack didn't you mention using anti-seize of the piston in one of the PDW threads ?

My agency has adopted the MPX and just issued a 9 page cleaning and maintenance procedure which includes cleaning the gas piston.

Another thought:

Has anyone seen differences in reliability between the 4', 8' and 16' barreled variants ?

I recently saw a MAC video (I know) about issues he had with a new MPX and the how using an MI taper adapter effected accuracy. He tried to buy a taper adapter from SIG but they stopped selling them and SIG CS could not tell him why. He speculated maybe SIG knew about the taper adapters causing issues and quietly discontinued them. This got me thinking about SIG discontinuing the 8' MPXs. In the recent TFB interview with a SIG executive, they asked why the 8' was discontinued. The reply was that " SBRs dont sell" which was curious as I'm sure most of the 8' MPX SIG sold were brace pistols. I'm curious as to whether SIG discontinued the 8" because the 4" guns ran better ?

If work hadn't adopted these I'm pretty sure I would have traded it in on an APC PRO by now.....

[Clusterfrack]

It seemed the hotter the ammo the better it ran and it seemed to work best with the +P stuff.

Anyone else had similar experiences with their MPX ?
@Clusterfrack didn't you mention using anti-seize of the piston in one of the PDW threads ?

It must have been someone else using anti-seize. @GJM? I don’t have an MPX, but my buddy has a troublesome one that does not work well with anything below 140 power factor.

[ranger]

I use antiseize on my MPX piston - I probably shared that on a post. Still no issues with mine using a variety of 115-124 FMJs. Mostly 115 FMJs over 5.1 WSF. Mine is a Gen 2 8 inch pistol (now SBR) and I also have an aftermarket 4.5 inch barrel.

[olstyn]

I asked the exact same question and was told that the MCX does not have a gas system issue because the rifle powder burns so clean, and the MPX has gas system issues because the pistol cartridges are quite dirty.

Sunday @JM Campbell and I got to shoot on a friends property and I took the opportunity to try a variety of loads in my 8' gen2 MPX before detail stripping and cleaning the gas piston. Each was a 25 round magazine:


1) Blazer 115 grain FMJ - multiple malfunctions
2) Speer Gold Dot 124 grain +P - No malfunctions
3) Speer Lawman 115 Grain +P FMJ - No malfunctions
4) Federal Synthtech 150 grain Coated Truncated Cone - Multiple malfunctions
5) Winchester Ranger 147 grain bonded JHP - Multiple malfunctions
6) Federal American Eagle 124 grain FMJ - No malfunctions
7) Federal White box (LE Contract) 147 grain TMJ (truncated cone) No malfunctions
8) Magtech 115 grain FMJ - No malfunctions

It seemed the hotter the ammo the better it ran and it seemed to work best with the +P stuff.

So then is the answer for competition 95 grain JHP bullets intended for .380 loaded into 9mm cases over enough CFE-Pistol to kick them along at 1400 FPS? (133 PF) Should be more than plenty of gas to run the system, loaded that hot CFE-P should burn pretty clean, and the MPX being gas-operated will tame down the recoil, plus it'll be way louder than any other PCC ever, so you won't have problems with shot timers picking up your shots. Win-win-win-win?

[HCM]

So then is the answer for competition 95 grain JHP bullets intended for .380 loaded into 9mm cases over enough CFE-Pistol to kick them along at 1400 FPS? (133 PF) Should be more than plenty of gas to run the system, loaded that hot CFE-P should burn pretty clean, and the MPX being gas-operated will tame down the recoil, plus it'll be way louder than any other PCC ever, so you won't have problems with shot timers picking up your shots. Win-win-win-win?

They seem to run fine on +P Gold Dot 124 grain and the Speer 115 +P. A Nato ball equivalent should do the trick.

Or SIG could release the 40 S&W and .357 SIG conversion kits they promised back in the day.

[HCM]

It must have been someone else using anti-seize. @GJM? I don’t have an MPX, but my buddy has a troublesome one that does not work well with anything below 140 power factor.

I use antiseize on my MPX piston - I probably shared that on a post. Still no issues with mine using a variety of 115-124 FMJs. Mostly 115 FMJs over 5.1 WSF. Mine is a Gen 2 8 inch pistol (now SBR) and I also have an aftermarket 4.5 inch barrel.

@ranger Thanks. Is it the ILWT barrel ? Also copper or silver/aluminum anti-seize ?

[Caballoflaco]

In 120 + years of automatically repeating firearm development there has yet to be a successful pistol caliber smg or carbine that uses a gas-driven piston operating system. I have my doubts that SIG is going to be the company that makes that happen,.