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Tuning JP SCS system for least dot bounce?

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I'm getting ready to order a GMR 15 with the short stroke standard SCS. I looks like that comes with 5 steel weights from the pics on their site. I currently reload my own ammo using a 124 fmj bullet at about 130 PF.  I know you can use combinations of steel and tungston weights and I have even seen different springs shown on their site also. Man, that's a lot of combinations to try to sort out.

Can anyone give me some guidance on how these variables work together? A good starting point would be a big help. Also, should I order any tungston weights to have for experimenting? Any other springs? Thanks

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Posted (edited)

FWIW, I have a GMR-13, and when I tried swapping out a couple of the tungsten weights for steel I found that I preferred it the way it was originally.  Used a 115 gr bullet with VV N320 powder at around a 130 PF.

Not saying that you may not come to a different conclusion...

Edited by LowSpeedHighDrag

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I'm gonna watch this thread closely. I'm using that setup and ammo and haven't swapped out weights yet but its on my radar though I have very little dot bounce.

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I’ve been playing with mine on the timer and my fastest splits with close hits on the target is with 4 steel and 1 tungsten. I would try 5 steel if I had a fifth one. This is with 130pf 124gr JHP using N320. 

 

I believe the short stroke kit I purchased to go from 4 to 5 mass was a 3 tungsten and 2 steel combination. I think it was softer shooting with that setup but not as fast grouping my double taps. In a match I haven’t noticed the gun recoiling any harder. 

 

I will probably play around more with it later but as of right now I’m happy with the setup. 

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Humm, I thought there'd be a lot of responses by now. Maybe most people don't play with the weights like I thought.

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I prefer SCS 5H5 Heavy (Short Stroke) and I use 115 gr bullet from Sellier & Bellot factory ammo. 

 

 

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On 4/7/2019 at 5:28 PM, egd5 said:

I'm getting ready to order a GMR 15 with the short stroke standard SCS. I looks like that comes with 5 steel weights from the pics on their site. I currently reload my own ammo using a 124 fmj bullet at about 130 PF.  I know you can use combinations of steel and tungston weights and I have even seen different springs shown on their site also. Man, that's a lot of combinations to try to sort out.

Can anyone give me some guidance on how these variables work together? A good starting point would be a big help. Also, should I order any tungston weights to have for experimenting? Any other springs? Thanks

My testing with various weight bullet and power factor combinations led me to 2 nodes. 5 steel is the fastest cycle with the least dot bounce, 5 tungsten is the softest cycle with very little dot bounce. If you want a compromise I'd do 2 tungsten and 3 steel. 

Any short stroke SCS will have less dot bounce than the standard 9mm. Every SCS has been 100% reliable with any ammo either I or others have put through it. Let me know if you have any specific questions. Always happy to help out. 

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On 4/8/2019 at 10:09 AM, Cowboy1629 said:

I’ve been playing with mine on the timer and my fastest splits with close hits on the target is with 4 steel and 1 tungsten. I would try 5 steel if I had a fifth one. This is with 130pf 124gr JHP using N320. 

 

I believe the short stroke kit I purchased to go from 4 to 5 mass was a 3 tungsten and 2 steel combination. I think it was softer shooting with that setup but not as fast grouping my double taps. In a match I haven’t noticed the gun recoiling any harder. 

 

I will probably play around more with it later but as of right now I’m happy with the setup. 

 

Hmmm.  I've been running 5 tungsten, but it would be worth retesting it with a few steel weights in the mix now that I've switched which powder I use.  I imagine different powders and bullets may give different results when tested, so, as always, YMMV.

 

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Yeah Lowspeed. some idea of which weights with which bullet/power factor set-up was what I was hoping for. Something like with X bullet at x PF 3 steel and 2 tungston work better, but with Y bullet at Y PF 4 steel and 1 T work better. ETC. ETC. Maybe people just haven't done that much testing with several weight combos.

 

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43 minutes ago, egd5 said:

Yeah Lowspeed. some idea of which weights with which bullet/power factor set-up was what I was hoping for. Something like with X bullet at x PF 3 steel and 2 tungston work better, but with Y bullet at Y PF 4 steel and 1 T work better. ETC. ETC. Maybe people just haven't done that much testing with several weight combos.

 

 

I'll report back after I do the testing...

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I think part of that is like most things its subjective, some will notice the recoil more than the dot movement and not everyone holds the rifle the same.

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Well, I ordered a JP today. I'll report back in a couple of months.

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Posted (edited)

Congrats I’m sure you will like it. 

Edited by Cowboy1629

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After shooting a few matches with the stock stroke buffer, I swapped it out for the short stroke.  The stock stroke was three steel and two tungsten, so I left it at that weight to compare.  With the stock stroke and my new 147 load, it was soft with no dot bounce but it was slow.  Same weight with the short stroke, it was definitely faster with a considerable impulse that didn't necessarily show up in the dot.  I increased the number of tungsten to four and will test tomorrow and report back.

 

MB

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On 4/10/2019 at 4:47 PM, LowSpeedHighDrag said:

 

I'll report back after I do the testing...

 

I've just decided to leave the short stroke SCS buffer alone, with the stock 5 tungsten weights.  Whatever the effect on dot bounce, I think it will reduce the wear and tear on the lower over the long run.

 

Correct or not?

 

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I have mine set up with two tungsten and three steel, I haven’t tested it with split times but it’s 100% reliable and stays in target and I know the follow up shots are quick. Before I upgraded with the short stroke kit I ran two tungsten and two steel so the set up is pretty close as it was stock but with way less felt recoil with the short stroke.

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I ordered the standard SS system with 5 steel. I plan on shooting light loads, about 130 PF.

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I think 5 steel would work fine with light loads. I have 4 steel and 1 tungsten running 130 pf. My next order I will pick up another steel mass just to see.

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Has anyone ran a box or so of factory ammo through their new gun first or just started in with their reloads?

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Mine has never seen a factory round.

 

Over 2500 rounds so far and not the first hiccup with the gun or ammo. 

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14 hours ago, egd5 said:

Has anyone ran a box or so of factory ammo through their new gun first or just started in with their reloads?

Feed it whatever you can. They will run damn near any load you like. 

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Tested four tungsten and one steel, the snappiness was reduced, still no perceived dot bounce and splits mostly at .16.  Went to five tungsten and this is where I'll stay.  No snappy impulse, no dot movement, same splits and runs great.

 

MB

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On 4/14/2019 at 9:26 PM, egd5 said:

I ordered the standard SS system with 5 steel. I plan on shooting light loads, about 130 PF.

 

Why?

 

IMO there’s a reason a 115 to 124 running around 140pf is really really common among verteran AR9 guys in USPSA.

 

It’s flat, accurate, and it runs the gun quickly with heavy & shortstroked actions.

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1 hour ago, RAVAGE88 said:

Tested four tungsten and one steel, the snappiness was reduced, still no perceived dot bounce and splits mostly at .16.  Went to five tungsten and this is where I'll stay.  No snappy impulse, no dot movement, same splits and runs great.

 

MB

This is also my experience and that’s why I stay with 5 tungsten. My best splits are .12/.13. when I use HIPERTOUCH ELITE.

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