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Nemesis Lead

JP GMR-13 vs Sig MPX for PCC

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Easy to put extensions (Dawson, TF, etc.) on the Glock mags for the JP too.

Now I just need Magpul to make a "D-69"...

(that's a 60rd 9mm Glock drum, or maybe even just 50)

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I did a bunch of research this week and ended up with the Mpx. I'm changing the stock, muzzle device, trigger, and adding a badger latch to the charge handle on it.

Sent from my iPhone using Tapatalk

Why the MPX over the JP?

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Man, I'd love to see what JP some of you guys have been shooting. My JP with every load I've tested has been as soft or even softer than the MPX I've shot. Plus mags are cheaper and it always runs, always.

Jon

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It was pretty cut and dry for me once I shot both of them AWLAZS.

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I have, the JP shoots everything you can feed it while the Sig requires more gas to make it run. You can reduce the loads in the JP, less recoil and still 100% reliable. A JP built rifle is $1600ish and Glock mags, no brainer after comparing side by side. And I love Sig's but this one doesn't make sense to me

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Im shooting 147gn Rainier Ballistics HP's with only 3.2gn of titegroup in the MPX with no issues. Out of a pistol with a 5" barrel those rounds are making 129 power factor.

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On March 23, 2016 at 11:25 AM, ctay said:

I've not shot the JP - or any 9mm AR for that matter but I recently purchased a MPX Carbine and shot the Zion Classic with it this weekend. My experience is that the MPX is very low recoil, accurate and fast. The experience is very similar to shooting a well tuned open gun. The MPX is a very dirty gun, which isn't really a big deal.

Overall it was a good experience. I'll start a new post to share my PCC experience.

Were you using the pistol lenth or carbine ?

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On 8/12/2016 at 10:34 AM, Snopczynski said:

Im shooting 147gn Rainier Ballistics HP's with only 3.2gn of titegroup in the MPX with no issues. Out of a pistol with a 5" barrel those rounds are making 129 power factor.

Seen issues with the MPX not running and being ammo finicky. I just took 1st place in open and tac optics at a local three gun last sunday using my JP 9mm It was a short range match on a 50 yard bay. Everyone else was using .223's except one AK. Ie the point is the recoil difference is not goign to cost you the match.


Pat

Edited by Alaskapopo

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4 hours ago, Alaskapopo said:

Seen issues with the MPX not running and being ammo finicky. I just took 1st place in open and tac optics at a local three gun last sunday using my JP 9mm It was a short range match on a 50 yard bay. Everyone else was using .223's except one AK. Ie the point is the recoil difference is not goign to cost you the match.


Pat

If that is a concern with the MPX then you can get the gas port opened up some, but as it was pointed out that hasn't been a problem for most. 

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On March 22, 2016 at 10:36 PM, Nemesis Lead said:

Anyone spend time on both guns who can comment on the recoil impulse difference? Gas gun would seem to be softer, but JP has been known to work miracles....

I recently built a 9mm AR on a quarter circle 10 glock mag lower. I went with a heavybuffers.com 8.5ounce carbine buffer and the extra buffer weight brought the recoil impulse down to very light and manageable. Also, something that made a big difference in my decision on which platform was the availability and cost of magazines. I run the ETS Glock 31 rd mags and can easily and relatively inexpensivly add an extension and have 35 round mags that will run in 5 guns I have. Unfortunately I haven't had any experience behind the MPX but some of these pros and the cost made my decision easy for the AR platform.  

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To each his own. You have a narrower window of operation on a gas system for a 9mm than you do on a blow back. You do have lighter recoil. Pick your poison. For me I will take reliability over a large spectrum of ammo and reloads.

 

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I definitely trust the JP Platform for an AR9, I would have bought the JP if I hadn't bought the MPX. However, I have found if you keep the MPX lubed, it runs, runs, and runs like a swiss clock (all while providing less recoil). Mine runs my USPSA/3Gun 9mm reloads. 147gn Rainier Ballistics bullet with 3.2gn titegroup on a federal primer at 1.135" OAL.

Edited by Snopczynski

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Well, now I'm in for a *mostly* JP GMR-13. JP lower with JP trigger installed, JP bolt and JP SCS built out with various other parts I had available. After match testing a full JP GMR-13, a JP internals gun and franken-AR9 in addition to the CZ and Sig I decided on an AR apttern with all JP moving parts. Since I had essentially all the other parts ready intended for another build that got delayed, it was an easy choice to go JP internals vs full JP. So now my PCC will have identical handguard, grip and stock as my 3-Gun AR and I'm beyond excited. 

As far as the different PCC options go, they are all fun as hell to shoot. The CZ needs either a CZC trigger or the HBI spring kit and some polish to be competitive, still the least expensive option with $20 mags. The CZ also ran every ammo I could fit in the mags, sub minor to major 9mm. My PCC will pull double duty as a first time shooter match gun though. A few of the smaller female shooters that shot the CZ didn't like the recoil of the CZ, but I'm a little heavier and it still felt like less recoil than a non-compensated 223. Oh well, the CZ is still insanely fun. The CZ also has the intangible cool factor of being charged like an 80's villain. 

The JP vs Sig "recoil" discussion is splitting hairs with minor PF pistol loads in a rifle. Could I feel a difference? Not with my minor production loads. Factory ammo, maybe? The MPX might have shot factory loads softer but I don't see any need to load a PCC tuned round AND a production minor PF round. GLOCK mags alone would have swayed me to the JP over the Sig but there is a bigger issue with the MPX. The deciding factor for me was the trigger and long term durability of the JP system. I know a couple of guys that have insane round counts on their JP triggers with no issues. The Sig stock trigger is heavy to the point that it needs to be replaced but may or may not compatible with drop in AR trigger packs. 

So in the end I'm going to with a JP for USPSA PCC and I'm incredibly excited! Build price for me was just under $1300 with 4 ETS 31 round mags and some fancier furniture.

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So like most people, I choice was between these 2 guns and I ended up going with the JP with a 14.5" barrel. I have a RMR that I dont use so that is going to be the optic I use for now. My reasons behind my decision.

1) The JP seemed ready to go out of the box. Comes with a pretty good trigger, no need to form 1 to get a comfortable stock, and overall less things need to be changed to fit my needs

2) Glock mags. I used to shoot a limited g17 so I dont need to by a bunch more mags

3) I run a similar set up for 3 gun (which im more passionate about) will help improve my 3 run skills 

4) Overall the JP is cheaper for me. I found a good deal on Gun Broker so all in I'm under $1500 for gun, shipping, and transfer and since I dont need mags, new trigger, stock etc thats all ill need to put into it. buy once, cry once. 

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On 3/22/2016 at 10:36 PM, Nemesis Lead said:

Anyone spend time on both guns who can comment on the recoil impulse difference? Gas gun would seem to be softer, but JP has been known to work miracles....

I have the JP 9mm carbine, and while it'd good, I wouldn't say they worked miracles.  The blowback system has more recoil than I was expecting.  Still experimenting trying to get the lightest load that will function in the gun.

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6 hours ago, STIboy said:

I have the JP 9mm carbine, and while it'd good, I wouldn't say they worked miracles.  The blowback system has more recoil than I was expecting.  Still experimenting trying to get the lightest load that will function in the gun.

Rather than changing the load, I changed the spring in the SCS.  I grabbed one of my extra 308 springs (red one I believe), cut it so it wouldn't bind and dropped it in the gun.  It still runs everything from 110 PF to 170 PF, is easier to manipulate, feels flatter and the dot definitely seems to move less.

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I love everything about the MPX but I ordered a JP. Having a few glocks and tons of magazines it made most sense. 

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1 hour ago, gnhowell1 said:

Rather than changing the load, I changed the spring in the SCS.  I grabbed one of my extra 308 springs (red one I believe), cut it so it wouldn't bind and dropped it in the gun.  It still runs everything from 110 PF to 170 PF, is easier to manipulate, feels flatter and the dot definitely seems to move less.

Interesting.  So you're saying that putting in a heavier spring will help with smoothing out the cycling?

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Very interesting! Will the spring kit from the 5.56 work? Or do you need to use the 308?

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My 14.5 GMR13 shoots super soft with Freedom 147s. Very reliable. Ive shot it side by side to a friends MPX shooting factory Fiocchi 124s. Not much difference in recoil. Its a none issue in my opinion.

 

Both are super fun guns. For PCC i'd rock a GMR. For range plinking cool factor the MPX.

Get both!

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On 10/25/2016 at 0:08 PM, Jmob50 said:

Very interesting! Will the spring kit from the 5.56 work? Or do you need to use the 308?

Based on the stiffness of the 9mm spring I felt that jumping to the 223 was a little too much so I went with the 308.  It could work but I'd use the strongest 5.56 spring.

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