Galun

with sport pistol it can, each click in the powder drop bar is about 0.05. You may very well be right on the pcc barrel more friction. I was used to rifle longer barrel = higher velocity. But at pcc velocity maybe friction has more impact.

i think he is talking about the Jp scs replacement spring. The manual states that the stock scs has the 85% spring, and it’s indeed the clear / black spring. https://www.jprifles.com/buy.php?item=JPSCS-PACK15

Went to the range today and tried a few loads I had left from prior load development for my gmr-15 (glad I saved those rounds during all these years!). Hope this helps someone. 3.5gn sport pistol / 147gn Xtreme CPRN / 1.15 OAL => 910 fps ES 56 SD 16 PF 133 3.4gn sport pistol / 147gn Xtreme CPRN / 1.15 OAL => 870 fps ES 65 SD 20 PF 128 4.98gn sport pistol / 124gn PD JHP / 1.15 OAL => 1259 fps ES 44 SD 18 PF 156 4.79gn sport pistol / 124gn PD JHP / 1.15 OAL => 1244 fps ES 30 SD 13 PF 154 5.9gn long shot / 100gn Xtreme CPRN / 1.15 OAL => 1390 fps ES 38 SD 18 PF 139 3.76gn long shot / 147gn Xtreme CPRN / 1.15 OAL => 852 fps ES 65 SD 27 PF 125 4.08gn power pistol / 147gn Xtreme CPRN / 1.15 OAL => 896 fps ES 57 SD 23 PF 131 I didn’t like the recoil feel of power pistol. There was no perceptible difference between long shot and sport pistol. I am probably going to stick with 3.4gn sport pistol which is my carry optics load. It actually makes a higher power factor in my P320, 131PF. Maybe I split the difference and do 3.45gn and only have one load for carry ops and pcc. Normally the 16” barrel should lead to higher velocity, but I suspect the 147gn Xtreme being 0.356” diameter leads to more friction. It behaved the same way in my GMR-15, the same ammo makes a lower power factor in the pcc compared to the pistol. My precision delta 124gn (0.355” diameter) behave more normal, higher power factor in pcc than pistol.

I would probably leave the 70 in it and be done with it. But note that my experience is still limited. I shot my friend’s gun and I just got mine. looking at the brass ejection pattern of the 60 in shooting my 131pf ammo, i would not trust it to be reliable over an entire match. It worked for both of us in one stage but the brass ejection was very close, some seem to be almost like falling out. wasn’t really focused on recoil, it’s already very soft. Was more focused on dot movement and there was very little. the chrono was almost spot on compared to my gmr-15. I am going to load up some rounds with long shot and see how it feels compared to sport pistol. Recipe is 4.2 grains 147gn 1.15 oal for around 130pf out of a gmr-15.

We didn’t use the 80 during the match but it would have been even more reliable since the 70 worked with low power factor ammo the entire match. I personally didn’t try 60 vs 80 during this match, I only shot the stage for fun after the match with the 60 and 131pf ammo. Will have more feedback after the next match in 1.5 weeks. Overall between the match and the practice afterwards I’d say we did 3-400 rounds with over 100 rounds with the 60 degree locking piece with 131pf ammo, and not a single failure.

Shot a match recently with a friend. 3.5gn sport pistol, 147gn Xtreme CPRN, 1.15 OAL => 131 PF. 70 degree locking piece ran flawlessly entire match. After the match we ran one of the stages twice with the 60 degree locking piece and it was fine, but brass ejection was a little weak and sketchy. Has anyone tried a slower powder like long shot? (They called it far shot in the 2017 pcc load development article, so I assume that’s a potential powder choice). For people with better technical knowledge, what would a slower powder do to this mechanism? In the gmr-15 the slower powder would theoretically produce more has to work the comp I think.

I tested a bunch of loads today using recipes suggested by others here. 4.8gr sport pistol (proxy to n320) is indeed low 130s PF out of a 5 inch barrel (shrouded to 16 inches). with the ultralight barrel I seem to get better groups (measured by bill drill) with low PF. I got the best group with 147gr using 3.6gr sport pistol making low 130pf.

Hi, can you share the recipe for the 115 gr? What powder and charge got you to 133 - 135PF? I got tuned ammo 147gr 130PF for the 14.5” pin and weld and there was minimal dot bounce. Switched to the ultra lite and there was a lot of dot bounce. Would love to try some 115gr loads. Thank you.

Thanks for this - makes sense. I had a good load at 147gr 3.5gr sport pistol pushing 890fps with a jp 14.5 inch barrel with the new vertical comp, and dot bounce was minimal. Then I switched to the ultralight barrel and dot bounce was quite bad. If the prvi load works for you then I will try to load some 147gr for almost 1000 FPS and see how it goes. Thanks!

Would you mind sharing your recipe for 147gr? Are you using 5.5” and 16” barrels? I am trying to tune out my dot bounce for 147gr but I only got it to 900 FPS for low 130s PF. Maybe that’s the problem, too low of a PF. Thank you.

I think shroud barrel and side charger will be available later. Gotta see the market reception of a $3350 pcc. If it is a meaningful improvement and people are willing to pay for it, then they introduce the $400 barrel add on and $600 side charger upgrade. If the launch fall flat then they wouldn't have spent money developing those options. It’s prudent market testing.

Surprised to see nobody talking about this yet. Preorder is available and pricing is out. $3269 for the competition version with their tube handguard and pcc compensator. $3349 for the steel challenge version with their mlok handguard and titanium compensator. Looks like net weight savings of around 7oz (0.4lbs). I had been told that the roller delay mechanism makes this shoot like a 22 with very little recoil, and thus the compensator really isn’t necessary. Even if I shoot USPSA, I should go for the steel challenge version due to the weight savings. https://jprifles.com/1.2.18_JP-5.php?menu_select=rif_buy_menu

Mine is 45 degrees but it doesn’t go out sideways far enough then bend 45 degrees, so it’s a little to the left of the barrel after I have a cheek weld. you just reminded me that jp makes one. I will order from them. Thanks!

Hi, I recently tried an offset mount and I like it. However the mount I have does not have the correct height over bore. Can anyone recommend one that works well with the jp gmr-15? Thanks! Thanks!

I just developed a load that I really liked out of my gmr-15 with 14.5 inch barrel and pinned new style compensator (the one with port on top). 5.9 grains of long shot, Hornady 0.355 100gr FMJ, 1.08 OAL. Makes around 140-145 PF. Great snappy feel, dot bounced back quickly and felt like it barely moved, flat and accurate.

I don’t have the ability to trap bullets. But yes, now I do suspect that the plating is falling apart with some powder. When I made that post I haven’t done accuracy testing yet, only chrono. This was accuracy testing at 50 yards. SP = sport pistol, PP = power pistol, LS = long shot. Heavy left to right crosswind. I just had a non magnified holosun 510c so I am sure there is some user induced error here. But it does give me a good idea on comparative accuracy of the projectile and powder combination. The optic was zeroed for 147gn velocity so all 115gn groups were ~3 inch high. The 147gn with sport pistol grouped surprisingly well - 8 shots with 3MOA, and 2 shots which I think is user error. It does make me think the higher diameter of the 147gn isn’t the issue. Power pistol, which was slower burning, drifted to the right due to wind (POA was at the top right target). Long shot, which was the slowest burning, drifted to the right even worse (POA was at the top left target). I suspect the plating with these two powders had fallen apart by the time it left the barrel, leading to an unstable projectile. The 115gn with the slower powder were fine. JP suggested 3MOA is achievable with their barrel, and I got 4 - 5 with a non magnified dot sight for all loads. With the 115gn I got the best grouping with long shot which was the slowest burning powder. The 147gn sport pistol had the best grouping, but it still drifted to the right a bit due to wind (POA was at center target). The 115gn generally didn’t drift at all, it stayed in the middle in line with my POA. Maybe the slower muzzle velocity made the 147gn more susceptible to wind? It’s a difference of around 250fps, only out to 50 yards... but whatever. Maybe I wasn’t accounting for wind until later. I just plugged the 147gn into ballistic calculator, at 880 muzzle velocity 10mph crosswind will cause 3.1 inch drift to the right at 50 yards. It’s the first time I’ve done pcc accuracy test, at my normal AR-15 load the same crosswind will cause only 0.1 inch drift. Next time I will make sure to feel no wind before I make the shot.

I saw that JP PCC load development article... and at first I had no idea what the powder were. When I finally saw someone said JP tested longshot, all those names finally clicked for me. I actually had some of their every single powder! I was able to replicate almost the exact results, off by 0.1 gn here and there. It’s an awesome starting point for PCC load development... if I had known earlier I would have saved quite a few laddered loads to find the sweet spot. I didn’t use Titegroup because I read that they run hot and burn up the bullet. I never liked titegroup in my 5” pistol anyways and I imagine in a 14.5” rifle it will be worse. I really like the feel of sport pistol with a 147gn bullet. Recoil impulse was almost non existent. But it makes very little sound, and I think cross wind will have an effect on far shots. I did compare power pistol and long shot with 115 gn plated bullet. With power pistol I got sub 5MOA, with long shot I got sub 4 MOA, all at 50 yards. That’s why I chose long shot. The recoil impulse of long shot also felt a bit better, like it’s more dragged out? It would make sense since long shot is the slowest burning powder. But it could also just be in my head. A PCC GM told me to pick the load that gives me the fastest splits at 25 yards with tight A zone hits. That’s really the ultimate test since everything at shorter distance will only be easier. This test takes all factors into account... accuracy of the load, recoil impulse, bolt cycle speed, dot movement, etc. Just pick the load that feels best at 25 yards and go with it.

I've got some successful loads with the JP GMR-15 with 14.5" barrel. All at least 5 shots. Hopefully this will help others. 1. 2.9 gn Sport Pistol / Blue Bullets FP 147 gn / 1.135 OAL => 869 FPS / ES 61 / SD 22 / 128 PF 2. 2.9 gn Sport Pistol / Bear Creek Supply Moly Coated 147 gn / 1.135 OAL => 878 FPS / ES 23 / SD 8 / 129 PF 3. 3.5 gn Sport Pistol / Xtreme CPRN (plated) 147 gn / 1.135 OAL => 889 FPS / ES 54 / SD 20 / 131 PF 4. 4.1 gn Sport Pistol / Xtreme CPRN (plated) 115 gn / 1.135 OAL => 1124 FPS / ES 52 / SD 19 / 129 PF 5. 5.0 gn Power Pistol / Xtreme CPRN (plated) 115 gn / 1.135 OAL => 1114 FPS / ES 74 / SD 24 / 128 PF 6. 5.1 gn Long Shot / Xtreme CPRN (plated) 115 gn / 1.135 OAL => 1142 FPS / ES 88 / SD 30 / 131 PF Going for either faster powder heavy bullet to reduce felt recoil, or slower powder light bullet to work the comp. Don't know which one I like more yet. My preference is to use the 3.5 gn sport pistol 147gn plated, and the 5.1 gn long shot 115 gn plated. Shot timer with sensitivity at 13 failed to pick up my 147 gn rounds. Had to boost sensitivity to over 20. Will likely have reshoot problems. Om a windy day I had some terrible accuracy problems with my 147 gn loads... like a 10 inch group at 50 yards all to the right of POA. I think the 147 gn lost too much velocity at 50 yards out. Probably fine for USPSA but not as a PCC in a multigun match.

I figured it out. It’s the bullets, 147 gr 0.356 copper plated Xtreme bullets. Sport pistol, power pistol, long shot, doesn’t matter what powder. Huge variance in velocity, extreme spread was 150-200fps. With long shot powder I even got some at 500fps. Using blue bullets 147gr 0.355, I got expected results. 2.9 gr sport pistol at 1.135oal gave 130PF with 2.3 MOA accuracy. Using bear creek moly coated 147gr 0.356, I also got expected results. 2.9 gr sport pistol at 1.135oal gave 130PF with 1.46 MOA accuracy. I think non plated bullets are ok with 0.356 since they are softer than plated. Just for fun, I shot the Xtreme 147gr 0.356 at 50 yards. Around 7 MOA. Fliers galore.

I verified al the “slow” cartridges out of the gmr15 with my Glock and they chronoed as expected. My practice round was 3.3 grains of sport pistol pushing 147gr bullet and it was 130pf. My load development ladder was 2.8 to 3.2 grains in 0.1 increments. The pf drop off of these rounds out of my Glock was as expected at around 4 pf per 0.1 grain. So I know the rounds were not mislabeled and had the correct charge as intended. However, with all the posts, I have a good idea what the culprit was. I was using xtreme 147gr copper plated round nose which apparently is 0.356 diameter. Out of the two rounds that chrono as expected in the gmr15, my friends reload was 3.2 grains n320 pushing a 147gr lipstick bullet, and the other was Winchester factory 115gr, both of which I suspect are 0.355. Billchunn posted his data on a working 147gr load, sure enough blues is 0.355. I am going to do the same ladder (2.8-3.2) with some blue 147gr RN I have, and I suspect they will act normal as expected. I had also pressed a ladder with Xtreme 147gr 0.356 using sport pistol, power pistol, and long shot, just to see how they work. I was amazed with the accuracy of the rifle despite the inconsistent chrono. It literally made one hole after 8 Shots at 10 yards. I think it’s probably the 0.356 diameter grabbing the rifling better.

Humm, so it works in the Glock because there is only 5 inches of match barrelZ. It works in the ruger pcc because it’s a cheap loose barrel and the projectile never really slowed down. It doesn’t work in the jp because it is a high quality tight match barrel so the projectile got slowed down. That actually make sense. Whew. Should I up the charge or use a slower powder? The powder is sport pistol which a lot of pcc shooters seem to use. But I have some power pistols and long shot that I can try. Maybe load them all to 130pf and find the one with the best recoil impulse / es / sd.

My first suspect was chrono issue. So I took my production match round and chrono it out of my match Glock 34, that I have done many times. Sure enough it was right at 130PF with good es and sd. It’s not the chrono. My next suspect was somehow the bullet was not accurate out of the barrel, going over the chrono inconsistently leading to poor readings. If this was the case there would be large groupings. Put up a brand new target behind the chrono at around 10 yards. It was like a tack driver making almost one hole. Rifle was very accurate. The other observation was very large variance in speed. In a 5 shot sample, the Glock was 885fps / es 18 / sd 5. The ruger pcc was 984fps / es 13 / sd 5. The jp was 753fps / es 167 / sd 65. PF out of the jp was as low as 91, for a round that made 130PF in my Glock. I suspect it’s something with pressure development vs timing of the bolt. Gas / pressure must have been lost from the back somehow. Hoping someone who really know how the jp system works might have a better explanation to help troubleshoot.

Got a head scratcher here, want to see if anyone have an idea. Load development for my new JP GMR-15 with 14.5 inch barrel. Using 3.3gr sport pistol pushing a 147gr bullet, I get 130PF out of my Glock 34, 139PF out of my ruger pcc (16 inch barrel), but only 110PF out of the JP gmr15. I had 4 loads of sport pistol to try in 0.1gr increments, and consistently see 10 higher pf in my 16 inch ruger (expected) and 20 lower PF in my jp (????) than my 5 inch Glock. Like, if the Glock makes 125PF, I’d see around 135PF in the ruger pcc, and 105PF out of the JP. Another person at the range gave me some reloads with n320 powder pushing 147gr and factory Winchester pushing 115gr. With both of these I get 10- 15 higher pf in both the jp and ruger than the Glock, as expected with the longer barrels. Somehow it seems it seems like sport pistol powder is the culprit. How on earth can a 14.5 inch barrel shooting my production rounds designed for Glock 34 at 130PF somehow make 20 lower PF in the JP 14.5 inch, but the same round makes 10 higher PF as expected in the ruger 16 inch?