JP GMR-15 or Sig MPX PCC final considerations

[Kwontanamo]

12 hours ago, RWV100 said:

I have a blowback style with all the brekke customs stuff and criterion barrel so very comparable to the JP and the newest model MPX and I have shot the JP and even the newest model not released had a chance to shoot.  
 

to me blow back guns all feel pretty similar the MPX is considerably softer I can shoot faster splits and move and shoot easier in matches.   
 

if I would have shot one before I got the blow back on I would have never bought it.  I like my blowback gun it runs great but the MPX seems like cheating after using it lol.  

Do you have the 4 or 6" compxtension? i'm looking to get the 6" myself

[mstamper]

I have owned 2 MPX's. if you do not do VERY regular maintenance on the gas system you will find yourself throwing the guns across the range because you just lost a match due to feed issues from the gas system not properly cycling the BCG.

I can tell you from first hand experience that it is very frustrating to have that happen to you. IF you have the time and effort to keep up with the maintenance then the MPX is a great platform.

 

I sold both of my MPX's and went and bought two JP GMR-15's, changed out the 5 stainless weights to 3 tungsten and 2 stainless and the guns shoot very flat and group way better than the MPX's ever did. People asked why I did not wait for the JP-5. I did not want to wait and only be able to afford one gun. I prefer to live by the mindset of 2 is 1 and 1 is none. I know the JP's are very reliable and are very forgiving maintenance wise but even with that, I prefer to have a complete back up. This allows me to shoot them both and they each behave identical and that also extends the maintenance cycle.

 

I have owned a DB9R that I heavily modified and also a PSA PCC. sold them both to get the sigs. I wish I had bought the JP's earlier.

[Fasthenk65]

18 hours ago, mstamper said:

I have owned 2 MPX's. if you do not do VERY regular maintenance on the gas system you will find yourself throwing the guns across the range because you just lost a match due to feed issues from the gas system not properly cycling the BCG.

I can tell you from first hand experience that it is very frustrating to have that happen to you. IF you have the time and effort to keep up with the maintenance then the MPX is a great platform.

 

I sold both of my MPX's and went and bought two JP GMR-15's, changed out the 5 stainless weights to 3 tungsten and 2 stainless and the guns shoot very flat and group way better than the MPX's ever did. People asked why I did not wait for the JP-5. I did not want to wait and only be able to afford one gun. I prefer to live by the mindset of 2 is 1 and 1 is none. I know the JP's are very reliable and are very forgiving maintenance wise but even with that, I prefer to have a complete back up. This allows me to shoot them both and they each behave identical and that also extends the maintenance cycle.

 

I have owned a DB9R that I heavily modified and also a PSA PCC. sold them both to get the sigs. I wish I had bought the JP's earlier.

sooooo true!!! I did the same but tried the Sigs twice.. still regret it

[Bdh821]

I still love my MPX. At PCC nats, the JPs had more malfunctions than my MPX on the super squad…. But I do agree it’s a maintenance whore

Edited December 26, 2021 by Bdh821

[2011BLDR]

MPX's are not hard to maintain, just different than Blowback:

• ultrasonic tank every 500-600 rounds
• under stand the system gas requirements (med burn rate powders (CFE pistol,N330,N340, 3N37) @145-160PF
• under stand the EXTRACTOR system requirements ( tension on the retaining pin is my indicator) and rebuild it ( Sig factory parts only for the insert, spring and O ring) before it fails
• understand that gas port erosion is a issue, starts to effect gas system  reliability at around 10,000-15,000 rounds, you can drop down to a .0520 restricted gas plug and keep going, and then down to a .0469 and keep going some more.

[egd5]

Sounds like a big PITA to me.

[Bdh821]

On 12/30/2021 at 9:35 PM, 2011BLDR said:

 

• understand that gas port erosion is a issue, starts to effect gas system  reliability at around 10,000-15,000 rounds, you can drop down to a .0520 restricted gas plug and keep going, and then down to a .0469 and keep going some more.

Care to elaborate more as I don’t understand restricted gas plugs for the MPX. What exactly does it do?  I have 50-60k thru one of my MPXs and has the original gas plug.. 

[TRUBL]

coming from a guy that literally HATES to clean guns.......I know that I've run 2000 rounds thru my MPX between total cleanings. I've taken the piston out every now and then to lube it but that is about it. Also......with my MPX, I have never run anything but factory ammo thru it.....it is flawless....period.

[2011BLDR]

On 1/1/2022 at 9:16 PM, Bdh821 said:

Care to elaborate more as I don’t understand restricted gas plugs for the MPX. What exactly does it do?  I have 50-60k thru one of my MPXs and has the original gas plug.. 

Gas port in the barrel is just forward of the chamber about ¼” in to the rifling, location was chosen for the 4” barrel to work, all of the lounger barrel lengths are adding dwell time and increasing port pressure that leads to port erosion over time.  The gas plug has an expansion chamber that fills with gas to delay extraction before the piston moves.  When that expansion chamber fills up with Carbon/Lead/Poly Coating you are reducing the volume and delay to extraction. I.E you are attempting to extract while the case is still expanded against the chamber walls. As the barrel port erodes you are in effect pushing more gas in to the expansion chamber faster and reducing the delay to extraction causing the same issues.

 

The slot in the gas plug is .117” that is intended to work with a new barrel gas port on a 4” barrel dwell time. ILWT has gas plugs with .0520” and .0469” holes in place of the .117” slot.

 

[Boomstick303]

I have heard using coated bullets in MPXs is one of the major causes for the malufunctions you see with them.  Fouling of the gas port. 

 

@Bdh821while you have had great success with your MPX many have not. I was an RO for the 2021 USPSA 2 Gun Nationals on a stage that was a PCC only stage. Of the 25-30 MPXs that ran through that stage for the competition only 5 did not have issues. The other 20-25 had at least one malfunction with many of them having more than one. From my observation many seem to be using the available match ammo, purchased on site which I believe was the 150gr Federal Syntactic with the flat nose.  Was it the ammo profile of the fact they were coated bullets I do not know.  I just saw a lot of malfunctioning MPXs. 

 

In in my opinion the MPX is far too unreliable especially for the casual shooter. Maybe Sig will fix those issues but for now I have zero desire to buy one. 

Edited January 3, 2022 by Boomstick303

[Bdh821]

I've had issues.  My MPX malf'ed yesterday which cost me a local club match win.  it was a pcc match too.  I'd say 150gr federal syntec ammo is the incorrect ammo for a MPX.  They're gas guns and 150gr ammo doesnt make much gas...

 

regardless, ive had good luck with my MPX', but I've had issues too, like all PCCs.  I have 3 MPXs tho.  1 practice gun, 1 match gun, 1 match backup gun. 

[Shootingaggie]

The syntech 150 is the only ammo that I have had issues with. N=1, but wanted to add to the conversation. 

[2011BLDR]

11 minutes ago, Bdh821 said:

I've had issues.  My MPX malf'ed yesterday which cost me a local club match win.  it was a pcc match too.  I'd say 150gr federal syntec ammo is the incorrect ammo for a MPX.  They're gas guns and 150gr ammo doesnt make much gas...

 

regardless, ive had good luck with my MPX', but I've had issues too, like all PCCs.  I have 3 MPXs tho.  1 practice gun, 1 match gun, 1 match backup gun. 

That 150gr  syntec is like 3gr of super fast powder designed for Production/Carry Optics  870FPS 4.5-5 " barrel (130.5 PF) ... when I tested it in a 16" MPX it only did 960FPS (90 FPS gain), most factory ammo gains 185-225 +FPS in the 16" barrel.

 

I have been running MPX's since the start of PCC in 2016.  give it the correct ammo ( correct burn rate to generate gas, no coated bullets), maintain the gas plug expansion chamber and the extractor( insert spring & O ring) and they run soft fast and flat like an Open gun with a stock..

 

I have 4 paired up 2 for major / travel matches that rotate every other match as primary and backup ( originally Gen 2's re-barreled to PCC's last year). 2 for locals run one primary other is a back up ( one originally Gen 2 re-barreled to PCC last year) other one was bought as a PCC.

[Bdh821]

52 minutes ago, 2011BLDR said:

That 150gr  syntec is like 3gr of super fast powder designed for Production/Carry Optics  870FPS 4.5-5 " barrel (130.5 PF) ... when I tested it in a 16" MPX it only did 960FPS (90 FPS gain), most factory ammo gains 185-225 +FPS in the 16" barrel.

 

I have been running MPX's since the start of PCC in 2016.  give it the correct ammo ( correct burn rate to generate gas, no coated bullets), maintain the gas plug expansion chamber and the extractor( insert spring & O ring) and they run soft fast and flat like an Open gun with a stock..

 

I have 4 paired up 2 for major / travel matches that rotate every other match as primary and backup ( originally Gen 2's re-barreled to PCC's last year). 2 for locals run one primary other is a back up ( one originally Gen 2 re-barreled to PCC last year) other one was bought as a PCC.

 

Thanks for the input.  I appreciate any info to be gained about the platform.   Did you shoot A2?   I would have loved to run into you if so..

[2011BLDR]

1 hour ago, Bdh821 said:

 

Thanks for the input.  I appreciate any info to be gained about the platform.   Did you shoot A2?   I would have loved to run into you if so..

Yea I did... I shoot Rio about ounce a month when a Tucson Match is Canx for whatever reason ( MD's are DOD and go TAD or the other range doesn't have the required #'s  to hold the Match)

[2011BLDR]

expansion chamber

Depth should be

 

[2011BLDR]

Depth should be

[usmc1974]

On 3/16/2019 at 10:04 AM, gose said:

I'd say that the JP isnt really more reliable, but more likely to work out of the box. If you get an MPX that runs, it will be just as reliable as a JP.

Doesn't that right there make it more reliable?

[Boomstick303]

43 minutes ago, usmc1974 said:

Doesn't that right there make it more reliable?

 

It makes sense if you don’t think about it..........

[usmc1974]

49 minutes ago, Boomstick303 said:

 

It makes sense if you don’t think about it..........

Yeah, OK but then what if 

[pjb45]

I have several JP and I am very happy with them.  

I brag about their reliability and accuracy.

During a large PCC match, a certain brand of 147s failed to feed properly.  Strange since all other brands and bullet combinations worked well in previous matches.  Lesson learned for me.  So 3 stoppages on about 4,000 rounds fired is fine.

 

I have RO'd several PCC matches and matches with PCC, my limited observations are JPs are more reliable.  My friends shoot the Sig and like it.

 

 

 

 

[Bdh821]

One of my MPX’, the gas plug hole was filled with carbon up to the notch for the barrel gas port. It would malf maybe once every 2-300 rounds. I may know a lot about these guns but still learn new crap all the time. Point being, I cleaned it out and so far I haven’t had any issues. It’s my practice MPX with the highest round count.  I’ll report back once I get more round count. It may be a while since it’s winter and essentially shooting comes to a hard stop where I live

[Sfisch0311]

I've owned AR-9s and an MPX. I am going to go back to the MPX here very soon due to how flat it shoots. I only shot JHPs out of it due to trying to reduce carbon build up. I never had a real issue with it at that point. It also was a Gen 1, so I upgraded the extractor pin and spring with an O-ring and it ran like a top at that point. I plan on purchasing a Competition model soon.

[rbx]

Checkout Leadstar.....I love mine!

[Bdh821]

14 hours ago, rbx said:

Checkout Leadstar.....I love mine!

Can you please tell us why it’s a better choice than a JP5 or MPX?