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General | More on the JPSCS | FAQ

JP Custom Buffer Springs and Silent Captured Springs

The “spoon over a cheese grater” sound emitted by modern sporting rifles whenever they’re charged or fired has always been one of the AR platform’s ugly blemishes and one we’ve worked ardently to eliminate.  After years of specially selecting buffer tube manufacturers based on the quality of their tubes’ interior finish, we opted to design and produce our own action springs with a perfect centerless-ground and precision-polished outside diameter.  These JP Custom Buffer Springs are an inexpensive way to see exactly why we have a reputation for having the quietest, smoothest rifles on the market.

Our pursuit of perfection didn’t stop with springs though and led ultimately to the creation of the JPSCS™ Silent Captured Spring (patented) in 2012. Maintaining all the benefits of our polished buffer springs and proprietary LMOS™ buffer, this combination buffer-spring assembly eliminates the friction of standard buffer components resulting in outstanding smoothness and sound abatement. What’s more, the spring is removable from the assembly for custom tuning, and both the AR-15 and AR-10 versions of the JP Silent Captured Springs are functional in rifle- and carbine-length operating systems. The AR-15 version fits and functions in any gas-operated AR-15 variant, regardless of caliber and the AR-10 version should fit and function in any large-frame AR-10-type platform. The JPSCS is not compatible with any 9mm AR variant or any blowback system using a solid (weighted) carrier.

Silent Captured Spring Selection Guide

Silent Captured Springs
JPSCS-15AR-15 Silent Captured Spring
Standard Version
JPSCS-15HAR-15 Silent Captured Spring
Heavy Version
JPSCS-15KJP Silent Captured Spring Builder Kit with Alternative Spring Pack (AR-15)
Standard Version
JPSCS-15K-HJP Silent Captured Spring Builder Kit with Alternative Spring Pack (AR-15)
Heavy Version
JPSCS-10AR-10 Silent Captured Spring
Standard Version
JPSCS-10HAR-10 Silent Captured Spring
Heavy Version
JPSCS-10KJP Silent Captured Spring Builder Kit with Alternative Spring Pack (AR-10)
Standard Version
JPSCS-10K-HJP Silent Captured Spring Builder Kit with Alternative Spring Pack (AR-10)
Heavy Version
JPSCS-9MM9mm Silent Captured Spring$149.95
JPSCS-SMSteel Weight for JP Silent Captured Spring$7.95

SCS Auxiliary Spring Rate Kits
JPSCS-PACK15Alternate spring pack for JPSCS-15
5 Alternate Spring Weights
JPSCS-PACK10Alternate spring pack for JPSCS-10
3 Alternate Spring Weights

Buffer Springs
JPS-OSCCustom Centerless Ground and Polished Operating Spring
Platform: Small-Frame
Length: Carbine Length
JPS-OSRCustom Centerless Ground and Polished Operating Spring
Platform: Small-Frame
Length: Rifle Length
JPS-OSC.308Custom Centerless Ground and Polished Operating Spring
Platform: Large-Frame
Length: Carbine Length
JPS-OSR.308Custom Centerless Ground and Polished Operating Spring
Platform: Large-Frame
Length: Rifle Length
JPLMBJP Low Mass Buffer
for AR-15-type rifles

Silent Captured Spring

One of my pet peeves is the sound of a wood rasp coming from my rifle. I find it totally intolerable, even though it is the normal sound of rifles from every other manufacturer. Over the years, we have spent a great deal of time hand prepping our action springs and extension tubes to get that near-silent, glass-smooth feel to our actions. Anyone who owns a JP rifle knows exactly what I mean since it's the most pronounced and immediately noticeable difference the first time someone handles and cycles one of our rifles; the operating system honestly feels like it's running on roller bearings. It's this obsession that we've taken to its natural conclusion after a couple years of thought, design, prototyping and testing our JP Silent Captured Springs (patented).

The best way to describe the results of this innovative system is the complete absence of mechanical feedback from the operating system under live fire and a smooth, silent feel to the rifle when you charge or manually cycle it. No rough, raspy sound or feel. No twang or vibration from the spring during live fire, just the beautiful sound of silence. Even in a very rough extension tube, the rifle runs smooth since the spring never contacts the tube, running instead on a guide rod similar to a 1911 guide rod system.

If you've followed the history of ARs, you probably remember the craze for pneumatic AR-15 action systems several years ago. Those pneumatic systems also made for a silent, smooth running rifle, but they had some fatal flaws that the new JPSCS effectively avoids. First, they stop working in the cold due to a little thing called Boyle's Law. The new JPSCS uses an old-fashioned, reliable spring system that works under any conditions and has an innovative buffer system that rides the guide rod with the carrier.

The second problem with the pneumatics is that they didn't have the dead blow hammer effect of a true buffer system. An AR-15 without a buffer is a malfunction waiting to happen. The dead blow hammer effect of the buffer is essential to preventing bolt carrier bounce resulting in ignition failure on account of the hammer impacting the firing pin while the bolt is not fully in battery during rapid fire or full auto fire. The buffer also increases the reliability of a rifle by "hammering" the carrier forward to press the action fully into battery even when the chamber is fouled. In the JPSCS, the buffer itself is "captured" in the assembly providing all the mechanical functionality of a standard buffer retainer plunger but with the fringe benefit of greater ease in cleaning and service that comes with a simple drop-in part like the JPSCS.

The JPSCS system is available for both AR-15 and LR-308/AR-10 systems equipped with carbine-length stocks and includes a spacer to allow fit and function in rifles with full-length stocks and extension tubes. Thanks to ease of assembly/disassembly, we also be offering substitute spring kits with a variety of spring rates to let you experiment to find the rate best suited for your particular setup.

I'm already switching every rifle I own over to JP Silent Captured Springs, so don't be surprised if you do the same once you've tried one.


Will the JPSCS function in a select-fire rifle?

As configured, the JPSCS doesn't work well in full-auto applications but we do offer heavy versions of both models that use heavier tungsten weights instead of stainless steel. The standard JPSCS is designed as a low-mass system, which doesn't have enough anti-bounce buffering for a full-auto platform like the M16. Bolt bounce is more critical on full-auto because the bounce interrupts the falling hammer, a problem which is compensated for by the heavy mass versions of the JPSCS. These can be purchased alone or in complete builder kits, and if you already own an SCS, we also sell the weights themselves with instructions on replacing them. For more on compatibility, see our SCS Selection Guide.

Will the JPSCS be compatible with my bolt carrier?

The only compatibility problem that we've encountered with the Silent Captured Spring is with the PWS carrier group. This is because the guide rod of the SCS needs to pass into the carrier during cycling, and the PWS doesn't have adequate space. Mil-spec bore for the rear channel of a bolt carrier is .625, but the SCS will work with carriers down to .530". For more on compatibility, see our SCS Selection Guide.

Do I need the heavy (-H) version of the JPSCS?

The extra weight of the heavy version translates into more reciprocating mass (i.e., deadblow effect) against the carrier, which aids reliability since it enlarges the operational window but also makes it harder to mitigate the movement impulse. The standard SCS with lighter springs will yield more dramatic improvements, but on some particular setups, it may lead to occasional failures such as the carrier not always going into battery. Every rifle is different, but we typically recommend the heavy SCS for short-barreled rifles (SBRs), suppressed setups and any rifle where the original manufacturer recommends a heavy buffer. Also, select-fire rifles will almost certainly require the heavy SCS. As a point of reference, having all three masses of the JPSCS-15 in tungsten yields about the same total buffer as an H2 buffer. For more on compatibility, see our SCS Selection Guide.

Which spring does the JPSCS come with standard?

The JPSCS-15 comes with a 15-85 spring, and the JPSCS-10 comes with a 10-110 spring.

Why does my JPSCS make a rattling sound?

In some cases, the movement of the sliding weights will make noise during cycling. The free movement of these parts serves to increase the dead blow or anti-bounce effect of the buffer. If the noise is bothersome, we can furnish an additional O-ring, which will eliminate the extra movement. The remaining dead blow effect should be sufficient for most rifles.

Does the JPSCS work with the Law Tactical folding stock adapter?

No, not as of the Gen. 3-M model.

How can I fix bolt bounce while running the JPSCS?

The best fix for bolt bounce is to change out the standard weights of the JPSCS for tungsten weights. While swapping the operating spring for a heavier one will help close the action after bouncing, it will actually slam the bolt harder and cause the bolt to bounce more rather than less.

Before doing anything, make sure to check the JPSCS protrusion. The JPSCS should have good tension against the bolt carrier when the bolt is closed so that it doesn't slide back and forth with the bolt fully closed. With the action open, the JPSCS should protrude from the buffer tube very slightly, 1/16" or less. If it's below flush then it won't reliably push the bolt carrier all the way to closed.

What size hex bit do I need to disassemble the JPSCS?

The screws on the JPSCS are metric (M5) and take a 3mm hex key. A standard pattern hex might fit very closely but will start to strip out the screw. The JPSCS is assembled with thread locker, so the screws will require a fair amount of heat to remove. If you can't get the screws out, contact us for assistance.

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