JP GMR-15 Which Bullet

[IVC]

Just prior to the lockdowns I managed to get a nice JP GMR-15 (their older, blowback model, not the new JP-5) and take it to the range to sight it in. But soon after, before I got to playing with different loads, first the lockdowns started, then the great component shortage. As I'm getting back into reloading and setting up various gear, I'm back facing the problem I had with the GMR-15.

 

The initial range trip was to sight in the red dot, off of sandbags on the bench. Can't remember whether I decided to sight it in at 25 yards (my usual for pistols) or 50, but I do remember that the accuracy was horrible. Think 12 gauge (and not even full choke). In all fairness, this was expected since I shot some 147 Blue Bullet reloads. They were not only slow (minor), but coated bullets and comps don't mix well. Before I had a chance to try different things, the ranges closed so it was all on hold for a couple years. As things are slowly getting back to normal, it's time to revisit the PCC and get a good load that will work reliably and have good accuracy.

 

So, here are the choices that I currently have, excluding coated handgun fodder, from lightest to heaviest:

 

• 115 Precision Delta JHP .356
• 115 X-Treme RN .356
• 124 Montana Gold JHP .355 (standard bullet for Open handguns)
• 124 Montana Gold CMJ .355 (base is covered in addition to having jacket, got them because they were available at MG)
• 124 X-Treme RN .356
• 125 HAP .354 (some overrun sold by Midway during pandemic, Hornady doesn't list .354s)
• 147 Montana Gold CMJ .355 (were in stock, bought them in case I need heavier non-coated bullet)

 

Which of these are likely to work well in the PCC? Note that HAPs are undersized for some reason, not sure if they were factory seconds or some special run sold through Midway. 

 

As for powders, I have a stash of N310 (for Limited major .40), 3N38 (for Open 38SC), N320 (for generic 9mm) and CFE Pistol  (will try for 9 Major Open). I'm thinking that N320 would be the most obvious choice, but I'm wondering if faster/slower works well with some types of bullets in PCC. 

 

[DwightSchrute]

Everything you listed will work, but if I were in your shoes, I would load the 124 grn. MG CMJs, starting with 4.0 grns. of the N320 at 1.120”.  I’m not big on thinly-plated bullets, and some people report feeding issues with hollow points in PCCs.  The heavier bullets can also be problematic if you’re not careful.

 

In general, I think PCCs are better off with lighter bullets and slower powders, and non-hollow point FMJs are preferable to hollow points and plated or coated bullets.  Opinions will vary; these are just mine.

Edited January 15, 2023 by DwightSchrute

[dtuns]

I have a GMR-15and I started with x-treme plated and my comp was full of the copper plating.

[old558]

I used 124gr X-treme plated with no problems. Very accurate for my needs.

[zzt]

If you want to use plated, use heavy plate.  I run Berry's and RMR heavy plate in my PCC with no problems at all.

 

N320 is the slowest powder I would use.  I'm not a big fan of the Precision Delta JHPs.  I'd use the 124 CMJs at around 132PF in general and the 147 CMJs at 144PF for all falling steel matches.  

[Dirty_J]

None of the top PCC shooters that are reloading are using slow powders. 
 

N320/Sport Pistol/Cleanshot/AA2 or even Titegroup  are the prevalent powders. 

[DwightSchrute]

OP, this is worth watching, and I would recommend listening to the whole thing.  It will give you some things to think about.  
 

 

[Dirty_J]

JP barrels are notoriously slow. 30-40fps slower than other brands of similar length. So I can see why they might recommend a medium burn powder… because they’ve gotta provide info that’ll keep their dumbest owner/reloader from having squibs. Larger volumes of slower burning powders gives a larger margin of error before you might get in to trouble. 
 

John Paul is right tho… heavy bullets and fast powders can get an inexperienced person in trouble fast. 

 

I suspect a bit of that video is damage control for JP customer service issues.  

I’ll reiterate … few (if any) top competitors are relaoding over a 124gr projectile and not one is using HS6 or CFE pistol. Max is the biggest exception… but he’s sponsored by a company that doesn’t make a PCC specific load… so the SuperVel 147 works okay in his JP5… because it’s not a direct blowback like the GMR15. 

Light bullets and fast powders is the way. 
 

 

[1911flyr]

My go to load for my GMR15, with short, was a 115 JHP PD with 4.6 WSF at 1.1. About 135-138 PF. Very accurate. This is also my load for the JP5. It is slower in the JP5 at 131-133 PF. No leading up the comp.

[IVC]

10 hours ago, DwightSchrute said:

OP, this is worth watching, and I would recommend listening to the whole thing.  It will give you some things to think about.  
 

Thanks, it's funny that he's looking at exactly the same bullets that I happen to have. My impression is that heavier bullets and coated-through-compensator are not the best choices, even though he talks about them. The video is about making power factor and not getting into trouble, more than it's about the best performance, but some good general information. 

[IVC]

22 hours ago, dtuns said:

I have a GMR-15and I started with x-treme plated and my comp was full of the copper plating.

 

12 hours ago, old558 said:

I used 124gr X-treme plated with no problems. Very accurate for my needs.

 

Interesting that it's two completely different outcomes. I haven't loaded anything with X-treme yet (just got them when they were in stock during shortage), to the point I didn't even realize they were plated and not FMJs. Doh! But I'll start with jacketed bullets to see what kind of performance I can get in general, then I might try to "downsize" to something cheaper if it doesn't sacrifice performance too much. 

[IVC]

9 hours ago, Dirty_J said:

I’ll reiterate … few (if any) top competitors are relaoding over a 124gr projectile and not one is using HS6 or CFE pistol. Max is the biggest exception… but he’s sponsored by a company that doesn’t make a PCC specific load… so the SuperVel 147 works okay in his JP5… because it’s not a direct blowback like the GMR15. 

Light bullets and fast powders is the way. 

 

2 hours ago, 1911flyr said:

My go to load for my GMR15, with short, was a 115 JHP PD with 4.6 WSF at 1.1. About 135-138 PF. Very accurate. This is also my load for the JP5. It is slower in the JP5 at 131-133 PF. No leading up the comp.

 

So both of you suggest 115s, and that is what I'm thinking about as a good start - 115 jacketed (PD JHP). Depending on results, I might try some 124s later, then try plated 115s just because I have them already. 

 

I've never used WSF, primarily use Vihtavuori and now got a batch of CFE Pistol, but it seems not to be the choice at the top, so likely not optimal for PCC. Since we are talking "fast powders," any opinion on N310 (the fastest I have, I love it for my Limited major in SVI - 4.3gn under 180 FP red coated SNS, getting about 171-172 PF)? Or should I stick to N320 and just find the load that gets me what I'm looking for? I reload on 1050 so once calibrated, it's pretty consistent and I check powder measure calibration before every session by pouring 10 charges together, then spot-checking from time to time a single charge. 

[Dirty_J]

I think n320 will be a mighty fine powder to fun for PCC. 
 

I’ve not personally played with anything much faster… but if you’ve got some n310… load some test rounds up and let us know! 
 

I load on an RL1100 and I get single digit SD/ES with my Cleanshot PCC loads. I have a similar process for QC checks on my powder measure as well. I think you’ll be fine. 

[MaX_1]

X-treme Bullets 135 grn JHP with N320, I get  950 - 970 fps. that keep it flat.