JP GMR-15 UL - PCC pointers and mods?

[falconpilot]

Recently picked up a GMR-15 ultralite - It's my understanding that the gun is already short stroked(from factory with JPSCS2-9SS-5). I'm assuming the 9SS-5 stands off 5 stainless steel. It's running the polished stainless JP 9mm Enhancedbolt.  Worked up a load with sport pistol under a 124MG running about 133pf...unless I'm really locking the gun in hard, I'm getting more movement than I was expecting. I'm new to the PCC game, so I'm looking for some tips and mods to get this rifle running the best it will...only thing I've done is add a Taylor Free mag well and bought a couple of TT plus 10 base pads-if I can ever get the damn pads off the 33 round glock mags I have...

 

Thanks in advanced!!

[ltdmstr]

I dunno.  I have a JP upper/lower/bolt/short stroke SPS with a 10.5 Faxon barrel and SLR linear comp and it's pretty much like a 22 with 130 pf loads.  I'd guess you're seeing/feeling the recoil more because it's an ultralite.  Not much you can do about that.

[Darqusoull13]

19 hours ago, falconpilot said:

Recently picked up a GMR-15 ultralite - It's my understanding that the gun is already short stroked(from factory with JPSCS2-9SS-5). I'm assuming the 9SS-5 stands off 5 stainless steel. It's running the polished stainless JP 9mm Enhancedbolt.  Worked up a load with sport pistol under a 124MG running about 133pf...unless I'm really locking the gun in hard, I'm getting more movement than I was expecting. I'm new to the PCC game, so I'm looking for some tips and mods to get this rifle running the best it will...only thing I've done is add a Taylor Free mag well and bought a couple of TT plus 10 base pads-if I can ever get the damn pads off the 33 round glock mags I have...

 

Thanks in advanced!!

Hey Jim, 

124's were always an odd recoil impulse for me in any of my PCC's. For whatever reason they seemed to be the anti-Goldilocks area of just too much recoil no matter where I loaded them. Sport Pistol will get them about as soft as you can for powder so if you're locked into the 124's due to supply constraints best advice I can give is to actually run around 140 PF. Running a bit above normal "safe" PF's did smooth things out for me at least. 

115's and 130's ended up being objectively less dot movement and recoil with the Ultralight barrel compared to 124's and 147's. The 115's ended up being light enough with enough gas to actually run the "comp" cut into the barrel but you do get a bit more dot bounce than the 130's. They 130's are my preferred load as they just seemed to be the perfect load with the 5S-SS, all 5 weights stainless and short stroked, SCS buffer. The dot objectively moved the least so for whatever reason, those are I ended up running. 

I also lock rifles into my shoulder hard. I don't necessarily do it 100% for recoil but it does mitigate recoil to an extent. Actually I found I was much more consistent over multiple rounds of aggregate scoring on drills shooting with a strong shoulder and frame. 

[falconpilot]

Darqusoull13,

 

Thank you for reply! That's the kind of info I'm looking for. I'm bump the power factor up some as 124's is all I got at the moment. Did you leave trigger stock?

 

Thanks again

 

Jim

[Boomstick303]

2 hours ago, Darqusoull13 said:

115's and 130's ended up being objectively less dot movement and recoil with the Ultralight barrel compared to 124's and 147's.

 

Are these coated bullets?

[Darqusoull13]

20 hours ago, falconpilot said:

Darqusoull13,

 

Thank you for reply! That's the kind of info I'm looking for. I'm bump the power factor up some as 124's is all I got at the moment. Did you leave trigger stock?

 

Thanks again

 

Jim

Yes, 100% factory install. 

 

19 hours ago, Boomstick303 said:

 

Are these coated bullets?

Coated, plated and FMJ in some cases. 

[falconpilot]

Well I ended up really liking PCC class, so I bought two more JP's - one comp ready from Shooters with vertical comp and another comp ready with 3-port side comp. I bought a spare JP 5H Short Stroke SCS as well to play with between the 3 guns since they come with the SCS but with 5 Stainless instead of the 5 Tungstens. While I love the JP15 Ultralite weight, for me, the comp ready guns with the14.5 barrels are the ticket - I settled on 4SS and 1T weight in each system. Loading 124MG to 133PF keeps boths bullets within inches apart double tapping fast as I can out to 15 yards or so. The Ultralite is alot hard for me to tune the dot bounce out. I'm waiting a JP's special barrel nut to into my 12" Smoke carbon tube. I've got their stock installed and its awesome..

[egd5]

I have the 14.5 barrel and use 124 at about 133 pf. I find that holding the gun tight to my shoulder is what works best for me too. And I too have the 5 steel, but I really would like to try with one T like Falcon pilot has. I'm just too lazy to mess with changing out the weights- don't want to mess things up.

[LowSpeedHighDrag]

FWIW I have a GMR-13, and I prefer the feel of 115 gr. bullets with it at around 135-140 pf.  (14.5” barrel + comp)

 

[rowdyb]

There is a reason you can buy different springs and weights for the JP system, to tune it. BTW, do you shoot the Benton gun club uspsa matches? There are guys there running JP guns who have made changes can help you in person.