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Thoughts on Potential JP GMR15 Build


JD23

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I am considering my first PCC and have mostly settled on the GMR15 after conducting research.  I have played around with the configurator and am hoping those experienced with the platform have some feedback regarding some of the options I am unsure about.

 

Thermal dissipator: Based on my searches, there seems to be a roughly 60/40 no/yes split on this option.  Obviously, the main downside is the additional 5 oz of weight added around the barrel to a gun that is already front heavy.  Under what conditions would the increased cooling become noticeable?  I am located in TX, so I would be shooting in hot temperatures for ~1/3 of the year.

 

Trigger: Roller trigger or flat trigger?  I generally like flat triggers and have no experience with a roller trigger.  I understand the potential benefit of the roller trigger, but I wonder whether the constant lateral movement along the trigger could be distracting, even if it doesn't cause shots to be pushed laterally.  Anyone with the roller trigger regret it?

 

Trigger spring:  Any reason not to go with the yellow 3 - 3.5 lb springs?

 

SCS: I'm looking at the short stroke SCS with the two tungsten and three steel weights, which is the mid weight option.  I shoot factory ammo, generally 124 gr, though also some 147 gr. 

Edited by JD23
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The thermal doesn't do anything on 9mm in my opinion, but it increases weight and reduces recoil. I run the standard JP trigger and love it. Tried all JP buffer settings (not all, many...) and finally settled on Blitzkrieg with the red Spring spring, short stroked. This with 124 plated RN bullets and RS12 powder (just a bit slower then VV N 320..) gives me least dot bounce off all I tried and the fastest splits. I love my JP!!

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I have several JPs, and while I use thermal dissipators on all of my big rifles, I don’t think they are necessary on 9mm. I don’t have one on mine, and don’t miss it. For fast shooting like uspsa, I don’t think the roller trigger is the right option.  I would also go with a 14.5” barrel with a pinned comp, and the lightest hand guard that is full length.  Also GET the extended mag release.  I can’t say that enough! This is one of the weak links compared to something like a Lead Star.  The standard mag release is very flat, stretched across a flat receiver, and you just can’t tell if your finger is on the flat button or not. If it’s half on and off, (and it’s really hard to tell without looking) you will not drop a mag to do a mag change.  I actually took jb weld and built up a ridge along the top and bottom of the button to cradle my finger and let me know where I was in the mag release.  You will love the rifle.  I have #2 on order.

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Unless you are shooting a thousand rounds an hour you wont need the thermal dissipator. I'm also in Texas and thats about where things get too toasty in July / August. 

 

Roller is an acquired taste to some. I like it but still prefer flat or curved. Go flat if you know you like flat. 

 

2 tungsten 3 steel is a nice middle ground, especially for factory 124s but that will run most everything. 

 

I use the competition / recreation on my GMRs and they light off small rifle magnum primers just fine. 

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If your going to put a party switch in it and go full auto get the thermal dissipater. Otherwise it would just be for looks. I've shot a gun with the roller trigger. It wasn't for me. I have a standard 3.5 lb JP trigger in mine and it breaks just over 3 lbs. I love it. I have the short stroke kit in mine. I'm not sure if I'm even good enough to tell the difference, but it's what all the cool kids have. 

 

I bought a ready rifle and added a short stroke kit, extended mag release, TF mag well and a Cmore railway. 

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Thanks for the feedback.  I'll scratch off the thermal dissipator and the roller trigger.  Now I have a question about the hand guard.  I was planning to get the standard rapid configuration handguard, but it appears JP recently made an M-Lok handguard available.  What is the consensus on the rapid configuration handguard?

 

I originally began considering the CZ Scorpion and then decided to move on to the GMR15 once I realized I would likely make quite a few changes to the Scorpion.  I am looking for something that is reliable and shoots well out of the box and the GMR15 seems to fit the bill based on what I've read.

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Ditto on the posts above re the dissipator, etc.

At the time I ordered mine they didn't have the m-lock handguard. I thought my gun was too front heavy so I splurged and bought a Smoke Composites carbon fiber handguard. It is WAY lighter than the JP one and makes my rifle feel much more balanced.

I have the 5 steel in mine but I shoot my reloads at about 133 PF. If you're shooting factory ammo I think the 3T 2S would be a good choice.

And I just have the standard competition trigger and it works great.

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fedupflyer--I used to have a Colt 6951 pcc before my JP. I would highly recommend going with glock mags. The colt mags are just a PITA to reload, finicky to get good working ones, and expensive. IMO, anyway.

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1 hour ago, egd5 said:

fedupflyer--I used to have a Colt 6951 pcc before my JP. I would highly recommend going with glock mags. The colt mags are just a PITA to reload, finicky to get good working ones, and expensive. IMO, anyway.

 

 

I am currently using a Colt pattern lower (QC10) and yes, the 32+ rnds are a pain to reload quickly, even with the magwell funnel. I think it may be costing me the difference between being a B to an M.

I just ordered a 20 rnd mag and hopefully that will help. So far, I have had zero problems with the Metalform mags. Other that if they hit the ground at the right angle they will puke up rnds.

I am on my third iteration of this PCC and it all started out as being a range toy.

If I get to shoot more, I may try the Glock pattern lower or maybe just a MPX....who knows

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The M-Lok handguard is 2.0 oz lighter than the MKIII Rapid Configuration handguard, so there is a benefit in weight, but not dramatic.  Another advantage is that attachments will be cheaper.  The thermal dissipator won't fit under the M-Lok, but that should be a moot point. 

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11 hours ago, fedupflyer said:

 

 

I am currently using a Colt pattern lower (QC10) and yes, the 32+ rnds are a pain to reload quickly, even with the magwell funnel. I think it may be costing me the difference between being a B to an M.

I just ordered a 20 rnd mag and hopefully that will help. So far, I have had zero problems with the Metalform mags. Other that if they hit the ground at the right angle they will puke up rnds.

I am on my third iteration of this PCC and it all started out as being a range toy.

If I get to shoot more, I may try the Glock pattern lower or maybe just a MPX....who knows

Haha, B to M, yeah, I used to think that too. Funny how that didn't work out like I thought. Yeah, I've picked up a few rounds too.

I'm guessing you have an investment in Colt mags by now, but I'd still recommend glock.

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GMR-15 16" Barrel, 18" w/ brake.

 

No Thermal Disipator - extra weight, not needed

 

Roller trigger or Flat Trigger - like the feel, personal preference.

 

SCS - Short Stroke

3T/2S - PF 140-155 pretty flat 

- 147 gr @ 922 fps NC Shooters

- 115 gr @ 1350 fps Fiocchi

Note: Waiting on another Tungsten weight to go 4T/1S.

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  • 2 weeks later...

My opinion:

I went with the drop in trigger, sounds like you are going with the separate components.  I wanted to be able to change trigger shoes, not sure you can do that easily with component trigger.  I orderd the flat trigger and love it but just ordered the roller trigger to give it a try.   The 2 Tungsten, 3 steel buffer is perfect for factory ammo, I use Fed 124gr most of the time, but it functions perfectly with everything I throw at it.  Zero malfunctions.  I didn't do the thermal dissipater, although the cool factor alone is probably worth it.  I fellow shooter with one doesn't think it does a whole lot.  I also went with the 14.5 barrel and a welded comp, saved some weight where it counts most.  I would have upgraded to the titanium comp if I had it to do over again.

 

Good luck. 

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I don't own a JP.  I decided against it, so take this with a grain of salt.  I didn't buy the JP because it was too heavy.  It was like swinging a log.  If you add the thermal fins it will be even heavier and swing like a longer log.  I like things balanced.  I went with a Leadstar Prime because it shot great, was super reliable and it balanced in my hands.  I went with the lightweight 16" SS barrel, because I intended to change it out for a Wiland LLW 5.5" barrel with shroud.

 

With the 16" and the carbon fiber handguard the balance is right between my hands.  It is slower in transition than the Wiland.  With the Wiland the balance point is just behind the trigge5.  It took a while to get used to this, but it transitions like lightning on steel challenge stages.  It is superb out to 50 yards, but I have trouble hitting 8" round plates at 100 yards.  The 16" barrel is slower to swing, but steadier.

 

I'm not trying to talk you out of a JP.  Before you plunk down your money based on reading and other people's opinions, go out a handle/shoot some.  The people I shoot with have everything from a basic Keltec to really expensive guns.  I handled a lot of guns and asked the owner why they chose what they did and what they would change.  Most shooters will let you try their gun.  Bring some factory ammo and try them.  Their gun might be set up for something else, but you still get a feel for how the gun handles and shoots.  You also get to check out the ergonomics.  Some things are not going to be comfortable, and some feel just right.  It's handy to know that going in, because swapping out parts later can get expensive.

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I own several JPs.  I saw some Sig working pretty well.  Simple questions and answers: would I recommend JP -- Yes; would I buy another--definitely thinking about it.

 

We just finished the AZ PCC match.

My observation from being on a stage for 8 squads or so is:

Colt mags are inferior to Glock.

I saw more issues with Colt mags than any other brand.  

 

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15 hours ago, pjb45 said:

I own several JPs.  I saw some Sig working pretty well.  Simple questions and answers: would I recommend JP -- Yes; would I buy another--definitely thinking about it.

 

We just finished the AZ PCC match.

My observation from being on a stage for 8 squads or so is:

Colt mags are inferior to Glock.

I saw more issues with Colt mags than any other brand.  

 

I'm jealous you guys have PCC matches!  I wanna move to AZ so bad and get away from this miserable New England weather and laws..  I've had a few friends move out there and say they wish they did 10 years ago.  Maybe ill get into A2 and get some nice weather shooting in a month

Edited by Bdh821
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On 10/7/2020 at 9:06 AM, Bdh821 said:

I'm jealous you guys have PCC matches!  I wanna move to AZ so bad and get away from this miserable New England weather and laws..  I've had a few friends move out there and say they wish they did 10 years ago.  Maybe ill get into A2 and get some nice weather shooting in a month

Brian, A2 is being held at the Prescott range. It will be cooler than down in Mesa.  The PCC match was a good time, much better than a pistol match with a carbine. :)

 

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I thought about going thru the build process when I bought my GMR-15 but decide the model from Ben Stoeger Pro Shop had all that i wanted on it. I got the 14.5" P&W and love it. YMMV but that option had everything i "needed" in a PCC. I am fine with the existing hand guard on mine. Fits my hand perfectly. Happy Shooting!

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On 10/9/2020 at 10:33 PM, Dan Sierpina said:

Brian, A2 is being held at the Prescott range. It will be cooler than down in Mesa.  The PCC match was a good time, much better than a pistol match with a carbine. :)

 

Still no word on getting in A2..  I look forward to next season and doing some PCC matches.  I hope you're enjoying the weather out there, Dan! I'd be lying if I said I wasn't jealous

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  • 2 months later...

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