JP Silent Captured Spring Problem

[kschwan]

I had the issue, but for me it turns out that it was the BAD lever I had on the AR. I took it off and it locked backed on my mags. I was able to actually turn the gas down. Nortic barrel, JP gas block, jp captured spring, lighted carrier.

[Todd7446]

Hmm - just getting ready to install one of the captured springs. Hopefully won't have these problems. Going to start off with it in a Magpul CTR and decide whether to switch to the ARFX stock.

[hpnewby]

Hmm - just getting ready to install one of the captured springs. Hopefully won't have these problems. Going to start off with it in a Magpul CTR and decide whether to switch to the ARFX stock.

Best of luck to you. The spring should suit you fine no matter if it's in a carbine or rifle length buffer tube since it's a fixed length. I cleaned out the gas tube and moved the gas block about 0.020" to try and get the port alignment perfect. Can't shoot til Monday, so we'll see what happens then.

[Todd7446]

Best of luck to you. The spring should suit you fine no matter if it's in a carbine or rifle length buffer tube since it's a fixed length. I cleaned out the gas tube and moved the gas block about 0.020" to try and get the port alignment perfect. Can't shoot til Monday, so we'll see what happens then.

Thanks. It's a brand-new Spike's Tactical that I've had on order for over 8 months. Shoots nice out of the box, but looking forward to experimenting. I'm thinking the next change will be an adjustable gas block since it came with a fixed block. Make sense? As far as recoil/lift management the other change I made was ditching the birdcage and replacing with a Seekins comp. It got the attention of the guys a couple stations away on Sunday.

[Brine0]

IMHO it seems that the JP spring system is not helping but instead introducing new variables to troubleshoot in the future. I get it and now there is zero advantage but i have introduced a new point of possible failure. If you have a variable gas block and the LMOS you are good to go those two are all you would need. At the most just use a light buffer in the receiver extension.

[latech15]

I hate that you guys are having all of these problems. I have built 4-5 rifles with Jp lmos bcg's, syrac gas blocks, and the Jp captured springs and never had any of these issues. As a matter of fact, I've never had any issues to speak of. I just start off with the gas block closed and open it up until it locks back on an empty mag and then go 1/2 turn more and rock in from there. I've used Nordic barrels, JP barrels, and black hole barrels all worked flawlessly.

[hpnewby]

i never posted an update, mostly because it didn't work. i had already checked gas port alignment before to no avail. The thing for me is that the gun cycles perfectly, just won't lock back unless i'm shooting commercial ammo. it doesn't work with CFE223 loads of any bullet weight or charge.

[dukduk]

i never posted an update, mostly because it didn't work. i had already checked gas port alignment before to no avail. The thing for me is that the gun cycles perfectly, just won't lock back unless i'm shooting commercial ammo. it doesn't work with CFE223 loads of any bullet weight or charge.

try different springs

[hpnewby]

try different springs

I would, but I haven't gotten around to trying, and no one has really reported that it fixed the problem.

[Mike Bell]

Got my JP recoil system yesterday installed it on my 16" Rock River upper and shot 60 rounds tonight with out any problems.

[apriav]

I two am interested in the fix....I have a CTR02 built by JP, Lmas bolt carrier and buffer, that has run great and runs great but it won't lock back on an empty mag with the recoil system. Gas block opened all the way. Just took it out and will wait for a fix.

[latech15]

The fix is more powder if it works with commercial ammo. The loads you are running chrono right? Meaning, are they significantly slower that commercial ammo? If you are going for super light loads, it may not work. Up the powder charge for more gas.

[Anthony Lombardo]

I am having the opposite issue with the LMOS Spring system. I built a 20" MATEN with a Brownells barrel and 7.62 Industries bolt. I can get the bolt to reliably lock back but after 250 rounds the spring on the LMOS was so weak it wouldn't reliably close the action 20% of the time. Any thoughts? I am considering switching to a Tubbs spring and heavy buffer,

[apriav]

I am shooting 69 gr SMK's @ 2800 fps?

[TitoR]

I had a similar situation with my JP Low mass buffer, BC, GB and tuned spring, combined with Carbon Arms 18" barrel and rifle gas system. With full gas, bolt will not stay open with an empty chamber and occasionally will have double feeds.

Fix - changed JP's tuned buffer spring for a regular DPMS buffer spring and avoided TULAMMO, use only brass cartridges. Not a perfect fix in IMO, but now I have a functional rifle. Gas block adjusted to 3/4 open.

Hope this helps.

[PursuitSS]

I am having the opposite issue with the LMOS Spring system. I built a 20" MATEN with a Brownells barrel and 7.62 Industries bolt. I can get the bolt to reliably lock back but after 250 rounds the spring on the LMOS was so weak it wouldn't reliably close the action 20% of the time. Any thoughts? I am considering switching to a Tubbs spring and heavy buffer,

Here's what works for me, LMOS Carrier, full gas, Wolff XP Action Spring.

When the carrier goes forward I wouldn't want a finger in the way!

[Anthony Lombardo]

On two separate Maten .308 builds my JP silent spring assembly doesn't have enough mass/energy to close the bolt reliably when shooting off a bench.

I basically have to turn the gas all the way open which negates the whole point of the adjustable gas block.

I changed it out for a Heavy Buffers buffer in one of my guns and it automatically started to work. 100% reliable now and able to tune the gas down which was my goal to begin with.

I am not sure the silent spring system is GTG on a standard bolt/carrier yet. At least thats my experience with 2 guns and 3 different BCG's

[Ming the Merciless]

I am having the opposite issue with the LMOS Spring system. I built a 20" MATEN with a Brownells barrel and 7.62 Industries bolt. I can get the bolt to reliably lock back but after 250 rounds the spring on the LMOS was so weak it wouldn't reliably close the action 20% of the time. Any thoughts? I am considering switching to a Tubbs spring and heavy buffer,

Check to see if the buttonhead screw on the captured guide rod has created a burr on the inside of the front weight causing it to drag on the guide rod.

[Brine0]

I have bought the JP LMOS and the JP captured spring unit since my last post.

I had problems with failure to lock back with 223 Rem. and 5.56 mm at first. I always start one shot at a time for safety. This in my opinion is park of the breaking in process for these parts.

The bolt carrier would not lock however it did eject. Tried a dozen shots or so.

Then I hooked up my 300 Blackout upper to this lower and fired one shot at a time and within 5 rounds it was locking back with no more problems.

The extra recoil from the 300 BLK upper with pistol gas system did it. Plus this 300 BLK upper had no muzzle brake only the AAC BLACKOUT 3 prong suppressor mount FLASH HIDER, thus more kick.

Switched uppers back to 5.56 mm upper and no more problems.

This worked on my buddies JP silent captured spring on his problem lower as well.

These were all new AR-15 units and bought at the same time. Shot in guns with with and without JP muzzle brakes it made no difference.

He had zero problems with the AR-10 unit.

So an alternative method if you experience any problems might be to take out the scs and cycle the unit with your hands several times before shooting any more shots then Lube it with KG4 or tetra gun oil. Reassemble.

Or shoot it with a 300 BLK upper one shot at a time till it starts locking back.

[dmshozer1]

I have bought the JP LMOS and the JP captured spring unit since my last post. I had problems with failure to lock back with 223 Rem. and 5.56 mm at first. I always start one shot at a time for safety. This in my opinion is park of the breaking in process for these parts. The bolt carrier would not lock however it did eject. Tried a dozen shots or so. Then I hooked up my 300 Blackout upper to this lower and fired one shot at a time and within 5 rounds it was locking back with no more problems. The extra recoil from the 300 BLK upper with pistol gas system did it. Plus this 300 BLK upper had no muzzle brake only the AAC BLACKOUT 3 prong suppressor mount FLASH HIDER, thus more kick. Switched uppers back to 5.56 mm upper and no more problems. This worked on my buddies JP silent captured spring on his problem lower as well. These were all new AR-15 units and bought at the same time. Shot in guns with with and without JP muzzle brakes it made no difference. He had zero problems with the AR-10 unit. So an alternative method if you experience any problems might be to take out the scs and cycle the unit with your hands several times before shooting any more shots then Lube it with KG4 or tetra gun oil. Reassemble. Or shoot it with a 300 BLK upper one shot at a time till it starts locking back.

Why are people dealing with this problem when all it does is do away with the recoil spring noise?

[MILDOTS]

I would not buy it for spring noise. The spring could be as loud as a jet and I would not hear it.

I have bought the JP LMOS and the JP captured spring unit since my last post. I had problems with failure to lock back with 223 Rem. and 5.56 mm at first. I always start one shot at a time for safety. This in my opinion is park of the breaking in process for these parts. The bolt carrier would not lock however it did eject. Tried a dozen shots or so. Then I hooked up my 300 Blackout upper to this lower and fired one shot at a time and within 5 rounds it was locking back with no more problems. The extra recoil from the 300 BLK upper with pistol gas system did it. Plus this 300 BLK upper had no muzzle brake only the AAC BLACKOUT 3 prong suppressor mount FLASH HIDER, thus more kick. Switched uppers back to 5.56 mm upper and no more problems. This worked on my buddies JP silent captured spring on his problem lower as well. These were all new AR-15 units and bought at the same time. Shot in guns with with and without JP muzzle brakes it made no difference. He had zero problems with the AR-10 unit. So an alternative method if you experience any problems might be to take out the scs and cycle the unit with your hands several times before shooting any more shots then Lube it with KG4 or tetra gun oil. Reassemble. Or shoot it with a 300 BLK upper one shot at a time till it starts locking back.

Why are people dealing with this problem when all it does is do away with the recoil spring noise?

I would not buy it for noise control. I could not hear the spring if it sounded like a Jet!!!!!!!

[Ogydog]

I have the JP buffer system installed in my DD. In the instructions they say you don't need the buffer detent and spring... However, went I took it apart to clean it I noticed that my detent and spring popped off and my JP was not staying in the tube...

I know why the detent popped out probably because the tube backed out.. but wasn't the JP supposed to stay in place since they say you don't need it....?

[Pfiddy]

The SCS will fall out with just gravity. It doesn’t need anything to retain it, the buffer retain8 g pin is to contain the buffer spring.  The JP is self contained. It might seem weird but you’ll get used to it. I’ve run SCS systems for years. They work great for me in many guns. 

[inertia]

Looking at this old thread was funny the problems these folks were having 10 years ago, we seem to have a much better understanding of these guns today than they did then. Also yes the SCS just floats in there, bolt carrier keeps it in place when assembled. Hope your spring and detent didn't end up in your reciever somewhere. 

[kurtm]

What's funny is that all these folks 10 years ago were figuring out these things so people 10 years latter could say they understand them better when they really don't. They are just repeating the stuff that they heard from those guys that really figured it out.