2scoops Posted March 29, 2017 Share Posted March 29, 2017 Looking for advise on tuning the buffer setup on my jp13 with 147gr bullets. What have you done ? Appreciate any all comments Link to comment
Aircooled6racer Posted March 29, 2017 Share Posted March 29, 2017 Hello: Yes I have and yes it works a lot better with 134-137PF loads. Lighter springs and lighter weights works for me. Buy the 223 spring kit and 2 steel weights. Try the different springs with 2 steel weights and 2 tungsten weights. Then try 3 steel weights and 1 tungsten weight. I am using the green spring right now on one setup. The other setup I have 3 tungsten weights and 1 aluminum weight I made with the black spring. Note I have not tried this on a actual JP rifle yet but have on my JP bolt setup rifle. Anyone know where to get just the JP single springs from? Thanks, Eric Link to comment
wgj3 Posted March 29, 2017 Share Posted March 29, 2017 I have done something very similar to Eric. I replaced a couple of the heavy Tungsten weights with the lighter steel versions. I also got one of the "tuner" spring packs and went to a slightly lighter spring. I definitely like how it has turned out. I am running 135gr bullets at around 132-135PF. Link to comment
latenightlegend Posted March 30, 2017 Share Posted March 30, 2017 How does running lighter steel weights affect the recoil or dot movement?Sent from my iPad using Tapatalk Link to comment
2scoops Posted March 30, 2017 Author Share Posted March 30, 2017 Appreciate advise. Going to try the proposed options and will provide feedback Link to comment
Malarkey Posted March 31, 2017 Share Posted March 31, 2017 On 3/29/2017 at 11:04 PM, latenightlegend said: How does running lighter steel weights affect the recoil or dot movement? Sent from my iPad using Tapatalk I would say the reduction in moving mass would lower the felt recoil and dot movement. Link to comment
wgj3 Posted March 31, 2017 Share Posted March 31, 2017 On 3/29/2017 at 10:04 PM, latenightlegend said: How does running lighter steel weights affect the recoil or dot movement? Sent from my iPad using Tapatalk Lower total reciprocating mass... same reason we cut up slides on pistols and take weight(s) out of buffer in DI AR's, etc. Link to comment
bluesman2a Posted April 2, 2017 Share Posted April 2, 2017 On 3/29/2017 at 4:13 PM, Aircooled6racer said: Anyone know where to get just the JP single springs from? Thanks, Eric I dimly remember reading somewhere that these use 1911 recoil springs. Haven't checked validity, but you could compare. You might look look at something like this and compare color codes. http://nictaylor00.blogspot.com/2014/08/1911-recoil-springs.html?m=1 Link to comment
Aircooled6racer Posted April 2, 2017 Share Posted April 2, 2017 Hello: The springs are about twice as long as a regular 1911 spring. Spring rates are close to 1911 ones used for a limited pistol. Thanks, Eric Link to comment
Old3GNR Posted April 2, 2017 Share Posted April 2, 2017 I looked at the buffer in my GMR-13 today. Looking at the pictures on the JP website, the matt finished (3) are tungsten and the shiney one is steel. I checked with a magnet and the steel seemed less magnetic, perhaps stainless. The spring was marked with red paint which doesn't match up with any in the assorted spring kit. I have only shot about 500 rounds but many double taps, dot movement does seem related to the buffer. Link to comment
Aircooled6racer Posted April 2, 2017 Share Posted April 2, 2017 Hello: The stock spring on the JP 9mm buffer is yellow on one end a red on the other. Yes, the shinny silver one is stainless steel weight. Thanks, Eric Link to comment
A6Gator Posted September 15, 2017 Share Posted September 15, 2017 Resurrecting an old(er) thread, but I was wondering if anyone has tuned their JP buffer for lighter loads. I'm running a .380 bullet in a 9mm case for Steel Challenge and it shoots pretty softly (a bit disconcerting at first), but was thinking perhaps going to a lighter spring and maybe another steel vs tungsten weight might make it even faster. I was surprised at the broad range of loads that the GMR-13 buffer will cycle, but, in this case, I'm trying to cycle things around 85-90 PF. Thoughts? Link to comment
Aircooled6racer Posted September 15, 2017 Share Posted September 15, 2017 Hello: Yes, I have played around with a lot of setups on the JP buffer. I would use 3 steel weights and one tungsten weight. Use the white or black spring but the green may work just fine. These are the 223 springs in the JP 223 kit. You will have to check if it feeds from the magazines ok and ejects the brass. You may want to up the power factor a little also. They get to the target faster that way. Thanks, Eric Link to comment
L9X25 Posted September 15, 2017 Share Posted September 15, 2017 When I first received my GMR-13, I looked specifically for a thread like this one but could not find one. I called JP and ordered the (3) spring pack, along with one steel weight and one tungsten weight. The guy seem puzzled why I would want another tungsten weight, but I ordered it anyway. After receiving the package from JP, I found the thread where Maximundo was commenting on his preferred set-up, but I did not have the springs that he recommended so I went with what I had. I felt the stock set-up was over-sprung so I went with the lightest of the 3 springs and replaced a tungsten weight with a steel weight (for 2T + 2S) for the lightest combination of weight and pressure that I could produce with what I had. That was a significant improvement over stock. There was far less dot movement and I did not feel any impact of the buffer bottoming out. After that success, I ordered the 5 spring pack so that I could go even lighter on the springs. I plan to go lighter until I feel the "hit" and then move back up to the sweet spot. I also hope to test out Maximundo's recommendations where he goes with a full tungsten buffer and the lightest springs of the 5 pack. While I would assume that having the lightest reciprocating mass would lead to the least dot movement, we have to remember that these are strictly blow-back actions and we need to keep the bolt closed until the bullet clears the barrel. I have been told that my gun released pressure from the ejection port in stock configuration, and reducing the buffer and spring weight too far would only make that worse. I will post my observations once I can get to the range. Link to comment
L9X25 Posted September 16, 2017 Share Posted September 16, 2017 Another observation, the heaviest of the 5 spring (223) pack is roughly equivalent to the lightest of the 3 spring (308) pack at ~13lbs, as JP claims. The 5 spring pack measured out at ~9-10-11-12-13 lbs at full compression with stock stroke. The 3 spring (308) pack is roughly 13-14-15 lbs and the gun is shipped with a ~15lb spring equipped. . Link to comment
mahamoti Posted September 17, 2017 Share Posted September 17, 2017 How are you guys going about judging which spring functions best? Ejection pattern? Timer? Felt recoil? Dot movement? I've got the stock SCS setup, and the dot barely budges with ~132pf ammo. But I also have the 223 spring pack and a desire to never leave well enough alone. I feel like with a lighter spring, something needs to be in place to slow down the bolt movement at the end of the stroke, like the wavespring setups. Link to comment
Aircooled6racer Posted September 17, 2017 Share Posted September 17, 2017 Hello: I use a timer and hits on target as fast as I can shoot at 7 yards. I shot a friends stock JP today and then tried my buffer setup in his JP. Same ammo for both and shots at 15 yards or so. His stock buffer gave me two shots about 8" apart and my JP buffer setup gave me 2" apart. recoil felt about the same with his 147 grain loads. I think with a stock JP PCC with the heavy hand guard a 124 grain bullet maybe better. My PCC shoots softer with my loads and buffer setup and also flatter. I will try his JP again tomorrow with some of my 145 grain loads and see. All this testing really depends on what works best for you. The timer doesn't lie and the hits on paper confirm if it works for you. Thanks, Eric Link to comment
HerdThinner Posted September 17, 2017 Share Posted September 17, 2017 On 9/15/2017 at 3:23 PM, L9X25 said: When I first received my GMR-13, I looked specifically for a thread like this one but could not find one. I called JP and ordered the (3) spring pack, along with one steel weight and one tungsten weight. The guy seem puzzled why I would want another tungsten weight, but I ordered it anyway. After receiving the package from JP, I found the thread where Maximundo was commenting on his preferred set-up, but I did not have the springs that he recommended so I went with what I had. I felt the stock set-up was over-sprung so I went with the lightest of the 3 springs and replaced a tungsten weight with a steel weight (for 2T + 2S) for the lightest combination of weight and pressure that I could produce with what I had. That was a significant improvement over stock. There was far less dot movement and I did not feel any impact of the buffer bottoming out. After that success, I ordered the 5 spring pack so that I could go even lighter on the springs. I plan to go lighter until I feel the "hit" and then move back up to the sweet spot. I also hope to test out Maximundo's recommendations where he goes with a full tungsten buffer and the lightest springs of the 5 pack. While I would assume that having the lightest reciprocating mass would lead to the least dot movement, we have to remember that these are strictly blow-back actions and we need to keep the bolt closed until the bullet clears the barrel. I have been told that my gun released pressure from the ejection port in stock configuration, and reducing the buffer and spring weight too far would only make that worse. I will post my observations once I can get to the range. Where is Maximundo's thread located. Link to comment
L9X25 Posted September 18, 2017 Share Posted September 18, 2017 3 hours ago, HerdThinner said: Where is Maximundo's thread located. http://forums.brianenos.com/topic/250677-which-recoil-system-jp-scs-gen-2-vs-mbx-pcc-buffer-system/ Link to comment
gnhowell1 Posted September 19, 2017 Share Posted September 19, 2017 I followed Max's recommendation and went with 4 tungsten weights, the lightest 223 spring (white), and then inserted CS100-M11 wave spring in between the white buffer and the back of the SCS. That had the best recoil impulse IMO and runs everything including 115gr subsonic steel challenge ammo. Link to comment
L9X25 Posted September 19, 2017 Share Posted September 19, 2017 45 minutes ago, gnhowell1 said: I followed Max's recommendation and went with 4 tungsten weights, the lightest 223 spring (white), and then inserted CS100-M11 wave spring in between the white buffer and the back of the SCS. That had the best recoil impulse IMO and runs everything including 115gr subsonic steel challenge ammo. How does that feel? Did that significantly reduce your dot movement? Link to comment
gnhowell1 Posted September 19, 2017 Share Posted September 19, 2017 9 hours ago, L9X25 said: How does that feel? Did that significantly reduce your dot movement? Best recoil impulse, most trackable reduced dot movement from all the combinations we tried. The blitzkrieg hydraulic buffer with a 308 carbine spring, a spacer and a wave spring was the only other combination we felt was as good or better. No doubt Max did his homework. Link to comment
SeattleDude Posted September 19, 2017 Share Posted September 19, 2017 (edited) 18 hours ago, gnhowell1 said: I followed Max's recommendation and went with 4 tungsten weights, the lightest 223 spring (white), and then inserted CS100-M11 wave spring in between the white buffer and the back of the SCS. That had the best recoil impulse IMO and runs everything including 115gr subsonic steel challenge ammo. I will have to try that! I have wave spring coming and have some jp springs laying around.... but need one Tungsten weight. Anyone have a spare you can sell me? =) Edited September 19, 2017 by SeattleDude Link to comment
2scoops Posted September 19, 2017 Author Share Posted September 19, 2017 Where did you buy the CS100 spring ? Do you have a photo of the setup ? cheers 20 hours ago, gnhowell1 said: I followed Max's recommendation and went with 4 tungsten weights, the lightest 223 spring (white), and then inserted CS100-M11 wave spring in between the white buffer and the back of the SCS. That had the best recoil impulse IMO and runs everything including 115gr subsonic steel challenge ammo. Link to comment
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