JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review

JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review Quick, easy AR upgrade that won’t break the bank An adjustable gas block might be the best AR15 upgrade, especially […]

JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review - packageJP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review

Quick, easy AR upgrade that won’t break the bank

An adjustable gas block might be the best AR15 upgrade, especially if you plan to run a difficult to tune setup like a suppressed AR. In this review we will share the good, the bad, and the ugly of the JP Enterprises JPGS-5BC Adjustable Gas System for AR15 and AR10 firearms.

The Problem – Your AR is too gassy!

Whether you hunt, are a tactical operator, a competitive shooter or have an AR for personal defense or recreation the biggest opportunity in most ARs to improve speed and accuracy is in reducing and balancing the forces which operate the semi-automatic rifle platform. So said the namesake of JP Enterprises, J.P. Gangl, a few months ago as we talked about the JP Armageddon Gear Roller Trigger in a JP-15 AR lower receiver (review) that was to be used in our Big AR Trigger Test (review). JP suggested that the ideal AR operating scenario is when the the buffer has just enough force to barely kiss the back of the buffer tube, but no more. While this is possible, almost no one sells a rifle that is configured this way, and for good reasons.

So many options, so many chances to over-gas your AR

JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review - Jeff shooting closeThe AR15 and AR10 rifles and pistols are like Legos with all of the different combinations of parts that can be assembled to give the operator any number of different functional and/or aesthetic weapons profiles. This flexibility comes at a price, as most AR builders prioritize reliable, consistent operation over little things like minimizing the recoil impulse. Not knowing what sort of ammo the operator will use, most builders opt to configure the AR to eat any and all possible ammo variants reliably. This makes sense, since the semi-automatic AR platform depends on a Direct Impingement gas system which requires a minimum gas port pressure in order to cycle. For any given cartridge some ammo varieties are much high pressure, while others are much lower pressure. Since this pressure is what cycles the BCG, ensuring that an AR will operate reliably on the lowest pressure rounds often means that when the same AR is shot with average or higher pressure rounds, the bolt velocity will be in excess of what is required to cycle reliably. Sometimes FAR in excess resulting in the dreaded “bolt slamming”. We call this condition “Over Gassed”. The additional energy sent aft in the BCG translates into additional recoil impulse which can be uncomfortable for the operator and generally moves the whole AR such that it is not possible to keep a clear sight picture while firing. Over-gassing an AR also subjects the internal parts to additional stresses which may contribute to premature failures.

Conversely, reducing the recoil impulse can make shooting more comfortable, cause less movement of the AR so the sight picture can be maintained while firing, and reduce wear on internal parts. In short, dialing down the pressure can make it easier to put multiple shots on target more rapidly and reliable.

How Direct Impingement gas system worksWhat the Gas Block does in a Direct Impingement gas system

As the name implies, the Gas Block often starts as a block of metal. It is machined to fit snuggly over the barrel and align it’s bottom hole with the gas port hole on the top of the barrel of the AR15, M16, M4 and similar rifles. In these rifles the Bolt Carrier Group (BCG) slides forward, strips a fresh round from the magazine, pushes it into the chamber as the locking lugs cause the bolt to cam against lugs in the barrel extension and rotate into battery. When the shot is fired and the bullet passes the gas port in the barrel a wave of high pressure gas travels up into the gas block where it is redirected aft through the gas tube to the upper receiver where the pressurized gas pushes the gas key on the BCG aft. The cam pin in the BCG causes the bolt to rotate off of the lugs and allows the bolt itself to slide aft in the upper receiver, taking the spent ammo case with it and ejecting it along the way. When the BCG has traveled fully aft the buffer spring pushes the BCG forward, starting the process over.
JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review - under JP MKIII handguardThat is a rather watered down, high level description that does not address a host of subtleties in the design and function of the Direct Impingement gas system. However, it should be easy to see that the gas block:

  • must pass sufficient pressurized gas to cause the BCG to move fully aft
  • must be strong enough to handle the quick blast of pressurized gas
  • must be machined to close enough tolerances to ensure that the barrel and gas tube connections do not leak

It might also be nice if the gas block:

  • is sized such that it can have a handguard installed over it
  • is easy to install
  • is adjustable

JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review - diagramWait… what? An ADJUSTABLE gas block?

In a standard gas block the diameter of the internal gas passages allows a certain amount of gas to pass through on each shot. In many cases, the passageway that the gas flows is over-sized to be sure that enough gas can pass, as too little gas will short stroke the BCG causing operational failures. One of the worst things that can happen in an AR is that the BCG fails to fully cycle. Remember, the AR design is designed as a battle rifle. Malfunctions are never good, but are especially bad when the operator is being shot at.

An adjustable gas block lets the operator fine tune for their specific ammo how much gas passes through the gas block, making it shoot more smoothly and extending the life of the parts.

  • Less gas: Make the hole smaller and the less gas passes. Less gas means the BCG is pushed aft with less speed and force.
  • More gas: Make the hole bigger and more gas passes, BCG velocity and energy are higher.

How we tested

UniqueARs GibbzArms G4 side charge upper review Lucid Optics M7 Newtown Firearms Bear Creek Arsenal R&J Firearms JP Enterprises - assembly handguardAR-15 build:

The entire Gear Report team have shot the Gibbz Arms G4 Side Charging upper build using the JP Enterprises JPGS-5BC Adjustable Gas System hidden under the JP MK III Hand Guard with Rapid Configuration Tube, most in a broad range of scenarios using various optics, ammunition types and other accessories (benches, rests, bipod, etc.). We shot standing, sitting and prone, still and moving, with magnified and unmagnified optics, with heavy and light projectiles, in warm and cool weather, rain and shine, rapid and slow – controlled fire… and even at night, specifically so we could see what kind of fireball the R&J Firearms Muzzle Brake produced.

Build details:

*Video* Here is a quick look at both of our Gibbz Arms G4 based builds and some dusk shooting we did shortly after completing the builds. Gotta love the fireballs shooting out of the R&JFirearms muzzle brakes!

JP Enterprises JP MK III Hand Guard Rapid Configuration Tube JPHG3-1M-RC Review shootingHow did the JP Enterprises JP Adjustable Gas System (JPGS-5B) low profile gas block perform?

Just as advertised. We have shot several hundred rounds since the initial adjustment of the JP gas block. After the first 20 rounds or so to break-in this new build we and have had no issues. The idea is to allow the operator to adjust the port pressure of the operating system for the specific ammo being used, and the JP Adjustable Gas System makes this rather simple.

Anything we don’t like?

  • JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review - unboxEase of adjustment:

    • While the adjustment screw is easily accessible through the JP Enterprises JP MK III 12.5″ Rapid Configuration Tube handguard (JPHG3-1M-RC), the tensioning set screw that prevents the adjustment screw from moving under fire is much harder to get to with the handguard in place. Technically, with a bit of allen wrench gymnastics it is probably possible to loosen the tensioning set screw, make any needed adjustments, then tighten the tensioning set screw with the handguard on. We found it far less frustrating to remove the handguard.
    • I would love to see JP offer a gas block that can be adjusted without tools via a knob, dial, lever, etc. While JP provides the 1/16″ allen wrench for adjustment and the T15 Torx wrench for installation, the less tools I have to keep track of in my range bag, the better.


In most cases we expect JP Enterprises products to carry a steep price premium. Higher priced parts usually get mentioned here since we may understand and appreciate that higher quality parts cost more, but we still don’t like paying any more than we have to. However, in this case, the $79.99 JP Adjustable Gas System is only on the mid-high end of what you might call “competitively priced”. A quick search on Amazon turned up a few cheaper options, as well as a number of adjustable gas blocks that appear similar, but cost more. Similar results are found when searching for “adjustable gas block” at trusted firearms retailer Brownells. I respect that JP doesn’t care that his products cost more than some other options. His goal, as he quite eloquently told me, is to make the best products for the AR platform, not the cheapest.


JP sent us the “black stainless steel minimized contour” version (JPGS-5B) for this build. It has clean lines and a nicely executed JP logo which compliments the overall look of this rifle build.

JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review - install gas tube

Josejuan lining up the gas tube to install the roll pin

How to install the JP Adjustable Gas Block

Installation of the JP Adjustable Gas Block was pretty simple with the clear, easy to follow, yet rather detailed directions provided. Remember that JP makes precision parts for professional competitors. Realizing the full potential of this level of parts requires more attention to installation details than some are accustomed to. Rather than rewrite those precise directions or summarize and risk missing something, I’ll just encourage you to read the complete directions in the package before starting and follow with care to ensure the best result. Nothing in the directions is that difficult, but there are a lot of little details to ensure that the JP Adjustable Gas System will operate properly.
It is not necessary to pin the JP adjustable gas block to the barrel. However, if you would like the added security, then there is a pilot hole that can be drilled to allow pinning.
Be sure that you order the correct size. This build used the .750″ bore adjustable gas block (fairly standard AR15 size), but JP also offers most of their adjustable gas block variants in .936″ bore.

JP_Enterprises_adjustable_gas_block_diagramHow to adjust the JP Adjustable Gas Block 

First, if the firearm will be used for Military or Law Enforcement type applications, then JP’s instructions  recommend “… running your rifle with the gas valve fully open so as not to compromise reliability.”
Adjustment starts with the gas block adjustment screw turned all the way in to cut off any gas flow, then loading and firing one round at a time and backing the adjustment screw out gradually to allow more and more gas flow on subsequent shots until the BCG reliably locks back. It is a pretty simple process that required about 10 shots to set… and probably could have been done in less. We installed the JP Enterprises JP MK III 12.5″ Rapid Configuration Tube handguard (JPHG3-1M-RC) over this gas block and found that while there was a hole in the handguard aligned just right to access the gas block adjustment screw, we could not reach the tensioning screw with the handguard installed. This was as simple as unscrewing the handguard tube for the duration of the adjustment period. If installing the gas block under a handguard that is difficult to remove and reinstall, then you might consider leaving it off until you are positive you are done adjusting the gas block.

The directions note it is optional to apply blue threadlocker to the adjustment screw to prevent it moving on its own. We opted not to use threadlocker and the adjustment screw has remained secure.

JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 Review - completeOverall

The JP Enterprises JP MK III 12.5″ Rapid Configuration Tube handguard (JPHG3-1M-RC) looks nice, is relatively easy to install and has functioned flawlessly on our Gibbz Arms G4 Side Charging upper test build. With the JP Adjustable Gas System, JP SCS buffer, Bear Creek Arsenal heavy barrel and R&J Firearms Keg Muzzle brake this rifle is obnoxiously easy to shoot and keep on target. We think that the top two upgrades for an AR should usually be a better trigger and an adjustable gas block. For the money, the JP Adjustable Gas System gets our vote as a great option.

Gear Score
The JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 is a great option to upgrade an AR for accuracy, speed, and reliability. If accessing the tensioning set screw to make adjustments were easier, this would be a 4.5

Gallery of JP Enterprises JPGS-5BC Adjustable Gas System for AR15 AR10 images:

Originally posted 2015-10-28 12:58:13. Republished by Blog Post Promoter

About Jeff

Jeff is the Editor in Chief of Gear Report and a National Shooting Sports Foundation Media member. He reports on the outdoor industry, reviews gear for camping, hiking, shooting, hunting, paddling, backpacking and other active pursuits. A USAF veteran, Jeff earned a MBA in Marketing and Health Services. He specializes in consultative selling and internet marketing. As the VP of BD & Marketing, Jeff provides sales and marketing leadership to MGECOM, Inc. and helps acquire new clients in need of solutions for online merchants in need of Affiliate Marketing program management. Jeff founded and manages Cress Sales & Marketing LLC, offering online sales and marketing consulting and services to online merchants and service providers.