JP GMR 15 Load, Changing Bullets

[IVC]

Playing with Hornady HAP 115's and N320, I got a load that worked really well for JP PCC - touching holes at 50 yards, limitation of the dot itself. The three loads I tried were N320 at 3.6, 4.0 and 4.2 grains, 115 HAPs at 1.143 nominal OAL. Only the 4.2 made minor, barely. I'll probably up it 0.1 grains and call it good. I'm not a fan of tinkering too much with something that works. I used the Vihtavuori load data on their page, which calls for 4.0 - 4.5 N320 @1.142 for XTPs, guessing that I should stay towards the lower end, just to be safe. 

 

The question is: If I replace HAP 115 with MG JHP 115, do I need to tinker with the load, or are they close enough so I keep the charge and the OAL the same? (The OAL is almost certainly going to change because of different bullet shape, but I can adjust it easily on the micrometer if there is need.) I have many more MGs than HAPs, so just looking for some first hand experience on where to start. I'll measure it and confirm, no matter what.

 

Today was a huge relief because when I last tinkered with this PCC, it had a nice *pattern* at 25 yards and it wasn't even a full choke. Lol. Those were fat, heavy, slow(ish) coated blue bullets. I'm guessing they were touching the comp baffles just enough to get all messed up. I was worried I might have gotten a lemon of a rifle, but now I know... 

[Tunachaser]

I would always run a ladder with different bullets even if very similar.  IMHO.  It's quick, easy and why not.  You could then go up the the 4.3 grs. you are considering. 

 

One thing to consider when changing bullets is the seating depth, which is not the same as OAL.  If the bullets are different lengths  then the heel of the bullet of the longer one will be further in the case, which means a smaller combustion area and, probably, higher pressures.

 

 

[Darqusoull13]

On 8/24/2023 at 5:32 PM, IVC said:

Playing with Hornady HAP 115's and N320, I got a load that worked really well for JP PCC - touching holes at 50 yards, limitation of the dot itself. The three loads I tried were N320 at 3.6, 4.0 and 4.2 grains, 115 HAPs at 1.143 nominal OAL. Only the 4.2 made minor, barely. I'll probably up it 0.1 grains and call it good. I'm not a fan of tinkering too much with something that works. I used the Vihtavuori load data on their page, which calls for 4.0 - 4.5 N320 @1.142 for XTPs, guessing that I should stay towards the lower end, just to be safe. 

 

The question is: If I replace HAP 115 with MG JHP 115, do I need to tinker with the load, or are they close enough so I keep the charge and the OAL the same? (The OAL is almost certainly going to change because of different bullet shape, but I can adjust it easily on the micrometer if there is need.) I have many more MGs than HAPs, so just looking for some first hand experience on where to start. I'll measure it and confirm, no matter what.

 

Today was a huge relief because when I last tinkered with this PCC, it had a nice *pattern* at 25 yards and it wasn't even a full choke. Lol. Those were fat, heavy, slow(ish) coated blue bullets. I'm guessing they were touching the comp baffles just enough to get all messed up. I was worried I might have gotten a lemon of a rifle, but now I know... 

Wouldn't bother changing too much except keeping the OAL within the acceptable range for any mag extensions you're using. IIRC the HAP and XTP were meant to be the same but who knows on the MG. 

Some coated bullets are better than others. 320 isn't terribly hot, but if you're running HiTek coated you'll get crud all in the comp. It's way worse with Titegroup. Reloading JHP's will avoid that whole mess. 

The Syntech poly coated are much better and don't leave crud all in the comp, but that's also probably partly due to the powder they are loaded with. I doubt you'll be able to find those to reload so unless you want to run factory JHP's are your best option. 

[Boomstick303]

9 minutes ago, Darqusoull13 said:

except keeping the OAL within the acceptable range for any mag extensions you're using.

 

Definitely make sure you do not skip over @Darqusoull13 comment regrading OAL. 

 

TTI mag extensions do not play well with OAL over 1.125.  I load to 1.120 to make sure if there is any variation I will not have any loading issues due to the magazines.  

 

I am loading a bit on the heavy end with the N320 because I am trying to get up around the 140 PF to run the 70 degree lock piece.  I cannot remember the exact load off the top of my head.  If you are interested message me and I will get you the load data for my current load with N320.

 

 

[IVC]

5 minutes ago, Boomstick303 said:

TTI mag extensions do not play well with OAL over 1.125.  I load to 1.120 to make sure if there is any variation I will not have any loading issues due to the magazines.  

Ugh, I'll check it out. I have several different magazines and extensions. Don't like the idea of loading to the magazine dimensions, especially if it's just the extension. Messing with the OAL will change the internal pressure and, in case of a PCC, might affect accuracy by changing the bullet jump. But if there is a feeding problem, I'll have to address it.

 

The magazine I'm using for testing is a BMX all metal magazine. That one will likely feed everything, much like their .40 magazines easily feed my 1.200" Limited major loads. But the stock Glock magazines, and especially the extensions... ugh again. 

 

Thanks for the heads up, I'll check it out. 

[Boomstick303]

Whatever you go with practice with a couple hundred rounds with all of the magazines you intend to use to vet them before going to a competition.  

 

Something else I noted with Glock magazines is I cannot fill the completely up when using extensions (TTI or Taylor Freelance).  I download 2 rounds if I am using bullets with a flat front profile, just like JHPs have.  The bullet dives into the front of the mage causing a malfunction.  Took me a bit to figure out what was going on.  It does not seem to be as much of a problem with bullets that have a round front profile like FMJ style bullets.  

 

I have never messed with the BMX magazines, so I do not know what issues those have if any.  

 

 

Edited September 14, 2023 by Boomstick303

[Darqusoull13]

18 hours ago, IVC said:

Ugh, I'll check it out. I have several different magazines and extensions. Don't like the idea of loading to the magazine dimensions, especially if it's just the extension. Messing with the OAL will change the internal pressure and, in case of a PCC, might affect accuracy by changing the bullet jump. But if there is a feeding problem, I'll have to address it.

It's a 9mm, not a 6 Dasher (even in a Dasher jump is over rated). Don't over complicate it. TF lists 1.125" OAL on their site if I recall correctly. Just be under that and you're fine. 

FYI bullet jump is basically irrelevant in the PCC. Without extensions, if you can fit in a GLOCK mag it will chamber in the JP. The difference in jump between 1.160" loads and 1.110" loads didn't have any appreciable affect on accuracy when I wanted to prove it the first time. It's likely because the relative change is minimal and again, you're going to need to run over 50 rounds of each load to tease any differences out of 9mm seating depth. Not worth the time. 

Reliability > all. Accuracy is important but if you're going from 1" at 50 yards to 1.5" at 50 yards to ensure 100% feeding at the mag body / extension transition it's worth it. Then again, I doubt many folks are using a Vortex 6-36 Gen3 for accuracy testing with bipod and rear bag like I am. 

[IVC]

21 hours ago, Boomstick303 said:

TTI mag extensions do not play well with OAL over 1.125.

So I checked some TTI magazine extensions and there was no issue feeding at 1.14x. But I only tested the basic 17 rounders with +5 extensions. I wanted to make sure first that the stock Glock tubes don't snag and to check the extensions where I can better see and feel if there is an issue.

 

Time to test some mega-zines, I'll post results in this thread so others can be warned if there are issues. 

 

[IVC]

3 hours ago, Darqusoull13 said:

TF lists 1.125" OAL on their site if I recall correctly. Just be under that and you're fine. 

The problem is that manufacturers change design and specs and I have some older ones. I'll test them and post results. 

 

3 hours ago, Darqusoull13 said:

FYI bullet jump is basically irrelevant in the PCC. Without extensions, if you can fit in a GLOCK mag it will chamber in the JP. The difference in jump between 1.160" loads and 1.110" loads didn't have any appreciable affect on accuracy when I wanted to prove it the first time. It's likely because the relative change is minimal and again, you're going to need to run over 50 rounds of each load to tease any differences out of 9mm seating depth. Not worth the time. 

Perfect - thanks. It's good to know that it's not sensitive because I really dislike tinkering with "combat" setups. They should work quite reliably within the combat parameters of reliability and accuracy. 

 

3 hours ago, Darqusoull13 said:

Reliability > all. Accuracy is important but if you're going from 1" at 50 yards to 1.5" at 50 yards to ensure 100% feeding at the mag body / extension transition it's worth it. Then again, I doubt many folks are using a Vortex 6-36 Gen3 for accuracy testing with bipod and rear bag like I am. 

Completely agree on all points - not only is reliability much more important, but even 1" at 50 yards with a red dot that is a couple MOA fits into the old fallacy of "measure with micrometer, mark with chalk, cut with an ax."

 

And if you mounted that Vortex on a PCC just to test loads, hats off to you - you have way more patience and OCD than me :-). 

[IVC]

Here's the verdict - it ALL worked! Phew. 

 

The external properties of the load are HAP 115 at 1.143" (varies up to 1.145" or so), trying steel MBX magazines and stock Glock polymer magazines, with MBX and TTI extensions. Turns out I don't have any TF extensions, so at least that limit doesn't affect me at the moment. 

 

From top to bottom: MBX 170 (or so) tube w/MBX extension, Glock 30/TTI extension, Glock 17/TTI extension, Glock 17/TTI base plate, stock MBX magazine.

 

The capacity was as expected, 56, 30+11, 17+5, 17, 23. I felt a slight snag when loading 30+11, but it fed without any issues or perceptible snag. 

 

Turns out I have a few more MBX tubes and extensions, but I expect them to all work the same as the largest one. Here's a photo of the stacked rounds: 

[IVC]

(wouldn't let me post two photos in a single post)...

 

[Wanna_Go_Fast]

On 9/13/2023 at 4:43 PM, Boomstick303 said:

TTI mag extensions do not play well with OAL over 1.125.  I load to 1.120 to make sure if there is any variation I will not have any loading issues due to the magazines.  

This is good to know.  Thank you