Sig MPX or JP GMR for PCC?

[Chutist]

The nearest range to my new home is big on 3 gun and PCC.  Thinking about giving it a go, work is crazy and I won't have time to build one.  I'll be lucky to find time to shoot...maybe reload.  Going to get the old 1050 set up and should be able to crank out some ammo when the time comes.

 

So I'm going to push the "Easy" button and just buy a ready to go PCC rifle.  I looked at the Nats Equipment survey and these two seem to be dominate choices.

 

Anything that puts one in front of the other?  I'm leaning JP since I have a bunch of Glock mags,  but don't know if I can get one? 

I have a line on a lightly used MPX....

 

 

 

[phoenixsomd]

For everyone I've known shooting a JP/blow-back AR-9 there hasn't been any issues with reliability. For ~40% of the folks shooting an MPX they've had at least one issue affecting reliability. It seems earlier version of MPX was more trouble prone with 2nd Gen or Competition models performing better.

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[TeedOff]

Just get a gmr15. It works of the box.

[jnr88]

I had a GMR -15 and sold it. I now have a MPX Gen2 and couldn’t be happier.i shot today and reflected how much I love the gun on the drive home. Hiperfire Eclipse trigger , Isler handguard and Magpul stock. You’ll be glad you did.

[Stephen7942]

I can't speak too much to the MPX but as for JP - GMR-15 it is an awesome gun! Has ran flawlessly out of the box for me. Zero hiccups so far. And a blast to shoot. I bought mine from Stoeger Pro Shop. Went with the 14.5" pinned and welded model. The are very well built and high quality rifles. Happy Shooting!!

[fyr4efect]

Ive had a FX-9 for the past year and it has been very dependable and accurate. Just got my GMR-15. Amazing. I see why competition shooters like these.

No experience with MPX.

[Chutist]

10 hours ago, jnr88 said:

I had a GMR -15 and sold it. I now have a MPX Gen2 and couldn’t be happier.i shot today and reflected how much I love the gun on the drive home. Hiperfire Eclipse trigger , Isler handguard and Magpul stock. You’ll be glad you did.

Every system has pro's and con's.  Both those rifles have huge followings, you don't get that without all the "big stuff" being right.  I'd read that the MPX had teething pains but that everything is sorted out with the Gen 2 and later guns. 

 

What made you sell the GMR and buy an MPX?  Must have been something to cause you to change platforms? 

Just trying to go in with my eyes open to the trade-offs. 

[TeedOff]

I’ve had 3 MPXs and one GMR.  I’m running built guns now. 
 

I got tired of the maintenance and unreliability of the MPXs. I had too many major matches ruined by failures. 
 

I then got the GMR because I wanted something that was known to be reliable.  The JP simply ran out of the box. I added an optic and a magwell to make it race ready.  I ran it for about 8 monthes, maybe 8-10k rounds and had no failures. During that stretch I made GM in PCC. 
 

I always loved the weight/balance  (once the barrel and handguard are swapped out) and how the mpx felt shooting.  The JP felt sluggish in transition and felt clunky in recoil. IMO the JP was about 2 pounds overweight for my liking. 
 

So then I built a PCC on a iron city receiver set.  This gun is a mix of the best things that I liked about both the mpx and the JP.  Using a 5/16 barrel, light handguard I got the weight to where it transitions fast.  I used a jp both and blitz buffer...very reliable.  I’ll admit I’ve had to play with bullet weights and powder loads way more than I wanted to but once I got that dialed in it cycles fast and the dot movement is about zero.  
 

So, if you don’t want to mess around...just want to shoot. Buy a JP and go have fun. 

[mrd]

1 hour ago, TeedOff said:

 I’ll admit I’ve had to play with bullet weights and powder loads way more than I wanted to but once I got that dialed in it cycles fast and the dot movement is about zero.  

Would you mind sharing what load you settled on, what length barrel and what buffer setup you're running?

[zzt]

When I bought a PCC I struggled with the choice between a JP and a Leadstar Arms.  A shooting buddy shot A Leadstar Prime for 1.5 seasons with zero malfunctions.  So I bought the same gun.  I don't regret the decision.  My gun weighs 5.5 lbs. with C-More Railway installed.  It transitions like lightning.  The JP is just too heavy (for me anyway).

[TeedOff]

16 minutes ago, mrd said:

Would you mind sharing what load you settled on, what length barrel and what buffer setup you're running?

 

Sure...your mileage may vary, objects in mirror are closer than they appear, etc.

 

Here is what I am loading for my “major match load”: 115gr RMR FMJ bullet, 1.125” COAL, 3.6 gr of titegroup. This gives me 1186 FPS/136.5 power factor.

 

I’ve tried bullets from 95 gr up to 150. I feel like in my guns the lighter bullets feel like they cycle faster with less dot movement.  I liked the feel of the 95 gr bullets but it requires a lot more powder. It felt good but was quite obnoxious (loud).

 

I’ve tested bullseye, clean shot and sport pistol in addition to titegroup. Clean shot and sport pistol both meter great and run clean. I happen to have a lot of titegroup on hand, so I’m just trying to use that up. Yes it runs a little dirty but on a blowback gun that is easy to clean up.

 

My main match gun has a very fast barrel, so I loaded a little hotter to make sure my backup gun would make chrono in case I had to use it in a major match.

 

Specifically on the match gun, I'm now running the Maxamundi barrel/comp and handguard setup.  That is a 10" Criterion barrel with a pinned and welded 4" comp.  The smoke composites handguard is low weight and slim...I like how it feels in hand and how the gun transitions.  Running the Blitzkrieg buffer...not short stroked (I had a problems with trigger reset when running it short stroked and haven't spent the time to mess with that).

 

The other thing that I should mention is that along with playing around with the gun and load I also paid attention to one of Max's videos on the lead up to PCC Nats where he talked about adjusting your stance and grip to make the gun return to zero more quickly...these minor technique changes along with the hardware changes have certainly helped my accuracy at speed in local matches.  Looking forward to major match season as the final test.

[jnr88]

Hi Chris, I sold the JP after deciding to stay with open. After that I developed familial tremors. I was forced to go to PCC. I figured I would try the MPX. As mentioned I’m extremely happy with this choice. Very low recoil and with the upgrades I made a joy to shoot. 

[biggulp]

If you want to mess around with swapping weights and working up specific loads and all the other "tuning" get the JP.

 

If you want to load mags and shoot and have basically zero dot movement, get the MPX.

 

I had a really well tuned QC10 build.  It was nice and accurate, but no amount of tuning made it "soft shooting" because that's just the nature of direct blowback. 

 

 

    

[Underwood]

My gen2 sig MPX is all factory with the exception of a handguard. Keep  the gas system clean and the bolt oiled, you will be fine.

I also had a built QC10 with all the bad a$$ stuff and it ran great, but nothing is as soft shooting as the sig MPX

[Chutist]

Reading all the replies.  Thanks for all the input. 

 

[Underwood]

[ck1]

I haven't shot my MPX in USPSA for a while now (concentrating more on pistol these days), but PCC brought me back to competition shooting after putting it down for a few years due to how fun it is! And IMHO, the MPX just takes what's already fun about PCC and makes it a total blast!

 

I put together a couple different AR9 builds before I bought the MPX, one going very budget-minded with Foxtrot Mike stuff (still the best stuff out there for the money IMO) and then one a bit more high-dollar running mostly QC10 stuff with JP guts, and beyond that I've put a bunch of rounds through buddies' fully Gucci'd-out GMR-15's and nearly bought one... 

But (and I know I might catch heat for saying this because I know guys are fond of them), IMHO the JP's are nice, but they're just another AR9, albeit a well put together one with "the name", there is nothing really special about them as compared to any other good blowback PCC that takes Glock mags. 

 

After shooting pretty much all of the PCC's out there, there's the MPX, and then there's everything else, full stop.

 

With how things are these days, and what MPX's are currently going for, I know I could sell my MPX and get every cent back I put into it and then some (and maybe/probably should due to accidently getting into PRS rifles lol), but I still pull it out for UML matches, steel sometimes, and just for laughs, and it's so much damn fun to shred with it that I just can't do it. 

 

 

[rowdyb]

Owned both, shoot with people who have both. Plug and play just get the JP.

 

The MPX is far to great a gamble for a match gun to offset how nice it is when it does work.

[Chutist]

So I'm getting the impression that the Sig is "nicer" shooting but has some reliability issues depending on Gen.  It also requires care to keep it running.

 

The JP is a simpler system, well sorted and understood.  Might be a touch less "comfortable" to shoot.  I was surprised to see a discussion of "recoil management" for a 9mm rifle. Interesting reading about the "short stroke" system.  Cheap Glock mags is a plus....and I might have one or two around.  LOL!!!

 

No "bad" choice just different.  

Part of it is going to depend on what pops up for sale, market is crazy right now. 

[grsdoug]

Over 15,000 trouble free rounds though my Gen II MPX. I have shot nothing but 124 PD JHP and 4.0 grain Titegroup. runs like a sewing machine. I have observed most troubles are with people running super lite loads, coated bullets, or messed with the springs/ports. I ran with the original extractor/spring for the first 12,000 rounds. I run a BCM spring/insert. The donut added too much tension. 

[Bdh821]

All my issues with the MPX Competition have been self induced.  The gun from my experience gets finicky when you put triggers in it that it doesn't like.  The only 2 that have been problem free are the factory Timney Trigger that was in the Competition model, or the Hiperfire Eclipse.  

 

I did have to make some changes to my ammo to get the gun to stay reliable.  Such as, switched from coated bullets to plated bullets.  Switched from Titegroup to HP38 which was recommended by Rob from ILWT.  I still think it's kinda dirty but not nearly as bad as TG.  I ran into extraction issues after about 15000 thru it, but it was because I had never cleaned behind the extractor...  I also replaced the factory recoil springs with new factory weight recoil springs.  

 

Overall, the MPX is an amazing PCC.  It just needs substantially more maintenance.  But I feel it's worth it.  

 

Also, I'll be honest....  The only reason I won A8 PCC is because I used the MPX 

[Underwood]

i also agree, most SIG issues are from owners users trying to run too light of loads or messing with the springs.  I also have 15k plus rounds through mine with zero issues.. What you should do is go to a match try a SIg MPX and JP and decide for yourself..  There is a night and day difference between the two..  The Sig MPX i can only describe is like shooting a M&P 15/22.. 

[MemphisMechanic]

2 hours ago, Chutist said:

I was surprised to see a discussion of "recoil management" for a 9mm rifle. Interesting reading about the "short stroke" system.

 

Recoil: First, on amount of recoil? Know that a 9mm blowback AR has more recoil than a gun chambered in a rifle caliber. 5.56 guns use a light bolt carrier which is unlocked by the gas tube acting on a mechanism after the pressure has dropped. A 9mm AR9 somply blows back, so it relies on a much heavier bolt and the resulting inertia. It takes tuning to prevent that reciprocating weight resulting in a significant jolt.

 

(The MPX is also gas operated, and therefore hilariously soft shooting compared to an AR9 like the JP. This is also the source of much of the tuning/reliability headache they can generate.)

 

For the second half? Sure the blowback guns have a sharper recoil, but it’s still a rifle shooting 130-150 powerfactor. The thing is, to win in PCC you need to rack up As really really fast given that you’re shooting as fast as Open guys... but are scored Minor.

 

PCC shooters strive to make the gun shoot with as little dot bounce as possible. Mine is pretty well dialed in, and with proper stance and grip I can shoot a doubletap out to 15-20 yards and expect a pair of holes well inside the A. One sight picture, rip the trigger twice while driving the gun hard, repeat.

 

THAT is why you hear discussions of recoil control from grown men firing 9mm through a gun which is three times the weight of a shadow 2... and braced against their shoulder.

 

 

Edited September 10, 2020 by MemphisMechanic

[MemphisMechanic]

(oops double post!)

Edited September 10, 2020 by MemphisMechanic

[Bdh821]

MemphisMech, you'd probably understand this more than the average PCC'er....  I picked the MPX because it was off the shelf ready for a LEFTY to shoot PCC.  I did some very minor modifications, Odin works mag buttons, buffer tube conversion and Magpul K2 grip.   The trigger isn't required but I switched it out anyway....    I have a SBR AR9 colt mag PCC and would rather use my MPX Comp.

Edited September 10, 2020 by Bdh821