Yet Another JP GMR15 or MPX thread.

[Underwood]

 Keep it clean and it wont let ya down                          

[LowBoost]

I need to re-read a couple of threads. I recall reading to run some parts wet and some others dry.

[Acer2428]

Also look around, there are mag deals to be found out there. Less so for Gen 2 mags, but I've found Gen 1 30 rd'ers for $30 shipped new and 20 rd'ers for $12.95 + shipping. Might see if your MPX will play nice w/ Gen 1 mags. Some do, some don't apparently. 

[Underwood]

7 minutes ago, LowBoost said:

I need to re-read a couple of threads. I recall reading to run some parts wet and some others dry.

Bolt went

Pistons dry 

[10cup]

11 hours ago, Smithcity said:

I compete with an MPX gen 2, I have a backup MPX, the JP is light on recoil if you reload and tune the gun.

 

I've been plagued by issues with the mpx.

 

I take delivery of my JP in a few weeks. I promise it is far more expensive to start with the MPX.

100% agree!  My experience exactly

[10cup]

22 hours ago, Aircooled6racer said:

I don't own a JP but have shot quite a few and they shoot well but need upgrades to make them better

Eric,

I find your comment about the JP misleading, can you explain.  If you were referring the MPX then I totally understand.  The JP does not need upgrades to make them better unless you just want to remove some weight.  The MPX needs a lot of upgrades and also is very front heavy in stock form so would like to hear your comments.  Thanks.

[Akkid17]

This seems to be a common argument, and it all comes down to a lot of opinions and anecdotal evidence. Patterns emerge over a long enough sample size and with that said the pattern seems to be:

-JP is a go getter right out of the box, if you don’t want/need/like to modify guns and just have them be reliable this is the route to go. 

-MPX has what most people consider to be 2 mandatory upgrades (trigger and stock, charging handle is debatable), however, it is pretty well agreed by the majority of shooters that have shot or owned both that the MPX is the softer/flatter option with very little dicking around with finding the “perfectly tuned load” and buffer set up. There have been complaints about reliability and some are probably user induced others are possibly the gun/gas system design. 

 

My experience is that I spent close to $2500 doing the full meal deal on a blowback gun with qc10 bones and all the go-fast cool guy upgraded parts then shot a MPX and proceeded to spend close to $3000 to get that fully set up with all the go-fast cool guy upgrades. If I were to do it again I’d skip the blowback gun and just go straight to the MPX and be much happier about my PCC life. 

[Akkid17]

Also, 2 other PCC shooters up here did close to the same thing. They bought the JP, then shot an MPX and proceeded to buy an MPX as well. 

[LowBoost]

@Akkid17:

 

Funny you mentioned it because even though I have the MPX K PSB version, I also threw some money at it with SBR tax stamp, stock, charge handle, trigger, Odin parts. I just haven't shot it much as I am not allowed to shoot it in 4.5" configuration at matches and with a suppressor, the shot timers usually don't pick up the shots.

 

I just thought why spend another $475 in a barrel + $300 in a handguard, when for some more I can have a complete rifle? I'll just shoot my MPX some more, clean it, shoot some more and see what I end up doing. FWIW, I have not had a single issue (yet) with factory 115, 124, 147 and my 124 Bayou reloads.

Edited October 8, 2018 by LowBoost

[Acer2428]

Why can't you shoot it in 4.5" config if it's a legal SBR with stock? Muzzle tucked under the HG?

[Aircooled6racer]

1 hour ago, 10cup said:

Eric,

I find your comment about the JP misleading, can you explain.  If you were referring the MPX then I totally understand.  The JP does not need upgrades to make them better unless you just want to remove some weight.  The MPX needs a lot of upgrades and also is very front heavy in stock form so would like to hear your comments.  Thanks.

Hello: The stock JP handguard is very heavy making transitions slower for most people. The buffer setup is too heavy and the spring is over sprung for 131-134PF reloads. I also think the comp is heavy as well. I run JP bolts and their 4 weight buffer that is lightened for my reloads. Hope this helps. Thanks, Eric

[Underwood]

I remeber the first time I shot a MPX.. I was running my JP equipped AR9 with my super soft hand loads at a match in South Texas.. After the match a fellow competitor and I were talking . She asked if she could try my PCC. I was like hell yeah..expecting her to say how smooth and soft it ran.. She was like it's got some kick. I'm thinking to myself you have to be kidding .. these loads barely make power factor. She said try my MPX.. wow.. full power loads = less felt recoil than my AR9 with my reloads. I bought a MPX after that.

Edited October 8, 2018 by Underwood
edit

[10cup]

1 hour ago, Aircooled6racer said:

Hello: The stock JP handguard is very heavy making transitions slower for most people. The buffer setup is too heavy and the spring is over sprung for 131-134PF reloads. I also think the comp is heavy as well. I run JP bolts and their 4 weight buffer that is lightened for my reloads. Hope this helps. Thanks, Eric

Thanks!  

[Akkid17]

1 hour ago, Underwood said:

I remeber the first time I shot a MPX.. I was running my JP equipped AR9 with my super soft hand loads at a match in South Texas.. After the match a fellow competitor and I were talking . She asked if she could try my PCC. I was like hell yeah..expecting her to say how smooth and soft it ran.. She was like it's got some kick. I'm thinking to myself you have to be kidding .. these loads barely make power factor. She said try my MPX.. wow.. full power loads = less felt recoil than my AR9 with my reloads. I bought a MPX after that.

Similar experience here, had my blowback gun fully decked out and loaded super soft with 135 gr black Bullets, then shot a MPX back to back using herters 115 gr that made 153 PF and the MPX with damn near major PF Ammo was softer and faster recovering than my baby loaded ar9. In fact I posted 2 personal records in steel challenge using the MPX that I was shooting for the first time that day. 

[BartCarter]

23 hours ago, Aircooled6racer said:

Hello: So for IDPA you can load to 30 rounds for stages that are only 18 rounds max? Why not just use Magpul 21 round mags or Glock 17 round mags with base pads. No need to have that extra mag length sticking out the bottom if you don'y have to. I find reloads are easier with the shorter mags also. Thanks, Eric

Actually, I have been using the Maglpul 21 round mags since you recommended them a long time ago.    They are easy to manipulate. 

 

I don't use extensions, I just reload.  So, depending on the round count, I usually start with a 33 Glock mag and have the 21 round for reloads on my AR9 Guard.  On my AR9 Colt I use 20 rounders when appropriate.  For me, the extra 10 rounds or so does not matter for the start or bother me with movement and I like to have "extra" just in case.  

[BartCarter]

On 10/7/2018 at 12:27 PM, BartCarter said:

...Of course you could run into IDPA match directors that hate PCC and find ways to cripple the division. 

 

We have two IDPA clubs in Las Vegas.  One doesn't allow PCC because they feel that IDPA is a pistol only sport.  The other doesn't hate PCC, but now (changed as of last match) runs  PCC with 10 round mags plus one chambered for start.  Looks like low capacity mags and a bunch of mag changes for me.  

[Shadyscott999]

I had a JP.  I now have 2 MPXs.  The biggest problem people have with MPXs is they think they are ar9s.  You can shoot 150 pf ammo through an MPX and it is  softer than 125 pf  through a JP.  

[Aircooled6racer]

Hello: The Magpul 21 round mags reload very nice for me. I actually did a couple of classifiers with master class hit factors with a PCC. I would use them for IDPA if you are limited to 10 rounds. Put some lead wheel weights inside the mags so they drop faster. Thanks, Eric

[BartCarter]

2 minutes ago, Aircooled6racer said:

... Put some lead wheel weights inside the mags so they drop faster. Thanks, Eric

 

Now that is something I never would have thought of.  

 

Time to experiment. 

[Smithcity]

Something to consider with all the advice people are providing, how many rounds do people have through said gun.

 

I have ~10k through one of my mpx's, started having a lot of problems around 5k rounds

 

Only ~3k through my second mpx, not many issues with it

 

Of those with higher round count JPs I've not heard of any issues.

[LowBoost]

Can you please elaborate on what issues are you having? How often do you clean your MPX, after everytime you shoot it?

[Smithcity]

5 minutes ago, LowBoost said:

Can you please elaborate on what issues are you having? How often do you clean your MPX, after everytime you shoot it?

I've had various issues:

1. The top half of My gen 2 bolt carrier separated from the bottom half and tore up the inside of the upper. Had to go back to sig. 

2. I clean my mpx every 200-400 rounds, oil it before every use, it will not run reliably past 400rnds without cleaning. Complete cleaning sucks as the gun breaks down into 20+ pieces

3. With reloads and factory ammo, the gun regularly fails to fully strip a round off the mag. Natural way to clear a malfunction is to charge the gun, with this particular situation, if you charge the gun you get a nasty double feed. Last time this happened I couldn't fix the issue during a match and zeroed the stage. Had to remove the upper to clear the jam

4. Right now I'm getting new grooves dug into my upper from the cam pin, something is wrong with the timing of the rotation of the bolt in the BCG, I'm sure it's the root cause of my malfunctions right now, itll be going back to sig.

 

I've had failures to eject, failure to go into battery, I've had the bolt lock up and needed a bore rod to clear the round. I've tried the normal gas hole size, opened gas port, reduced gas plug, different recipes for reloads (it likes slower powder), factory rounds, etc...

 

One guys experience. Others at the club run the mpx and are plagued with issues. One has an mpx that runs flawless but it had a low round count.

[Underwood]

I was told its a good idea to change all the springs in your MPX after 5,000 rounds. All the parts are available at   https://www.inleadwetrust.com/collections/mpx-parts?page=1

I am past that round count and haven't had an issue with mine ever. But i plan on changing all the springs this year 

[Smithcity]

26 minutes ago, Underwood said:

I was told its a good idea to change all the springs in your MPX after 5,000 rounds. All the parts are available at   https://www.inleadwetrust.com/collections/mpx-parts?page=1

I am past that round count and haven't had an issue with mine ever. But i plan on changing all the springs this year 

Sig disagrees, regardless, I've done exactly that, solved 0 problems for me.

[Akkid17]

Damn! Sounds like you got a lemon,

 

 

There are 5 of us running the mpx here, all in the 5k to 16k round count range, and the first issue someone had was breaking a trigger after 14k and the company replaced the trigger for free. I suppose we had another problem with a leading issue from one guy running bare lead Bullets and it gummed up his gas system pretty bad. Came back to life after he cleaned it out though.