Superlative Arms Retrofit AR15 DI Piston Upgrade Kit Review
What is a Piston Upgrade Kit for an AR15?
Most AR15s are built with a “Direct Impingement (DI) gas system”, the mechanisms that allows the bolt to unlock and the bolt carrier group to cycle after each shot. DI systems can be dirty, finicky and prone to failure, especially if a silencer (link to SilencerCo) is used. Replacing the DI system with a piston driven gas system can make the firearm run cleaner and more reliably. An AR15 Piston Upgrade Kit (Brownells link) includes the parts required to convert a DI AR15 to a Piston driven AR15.
Who needs an AR15 Piston Upgrade?
“Need” is a rather subjective term. In my experience with a wide range of AR15s I have not witnessed DI gas system failure. I have read about it happening and know people that have experienced a DI system failure… it just hasn’t happened to me. In fairness, I am somewhat new to the wonder world of AR15s, having only used ARs for about 4 years. So, when I say that piston systems are supposed to be more reliable, I see this as a logical argument more than one based on personal experience. Since a piston AR system delivers less of the dirty, carbon laden exhaust residue into the BCG area, there is less chance that the carbon will gunk-up the works and cause a failure.
However, theoretical reliability improvement is not the reason I wanted a Piston Upgrade kit for my AR. Since building the SD Tactical Arms Form 1 Silencer (review link) I rarely shoot an AR without the silencer attached. The silencer creates additional back pressure in the DI gas system which causes more carbon filled gasses to leak out of various places on the AR15 that are near my face. Hot, gritty gas in the face is not fun. The promise that swapping the DI gas system for a SupArms Piston Upgrade Kit would reduce the amount of nasty gas in my face was enough to motivate me to reach out to Superlative Arms.
AR15 Piston Upgrade Kit Installation
Tony at SupArms asked that I send him the AR15 upper that the SupArms Piston Upgrade Kit would be installed on. My plan was to send one of our testbed .300 Blackout AR15 uppers. However, Tony suggested that we start with the AR15 kit for a .223/5.56 upper, since he had plans in the works for an improved kit tuned specifically to the .300 BLK in the near future. Sending the complete AR15 upper would allow Tony to be sure the installation was done by the book and to test the upper for functionality before sending it back to me for review. As a shade-tree gunsmith, at best, I jumped at the chance to have a pro do the work.
Per Tony’s suggestion, we opted for a clamp on gas block since it is easier to ensure a good seal over the gas port on the barrel. I have since taken apart the Piston Upgrade Kit a couple of times as I attempted to swap a different handguard onto the upper. Installation is pretty simple and requires very minimal tools (whatever is required to remove your handguard and the supplied allen wrench to tighten the gas block clamp screws). You can also drill an optional set of gas block screw alignment dimples in the bottom of the barrel to ensure the gas block is aligned with the gas port any time the gas block is reinstalled. Drilling alignment dimples is a recommended “best practice”, not a requirement.
Sadly, I found that the new handguard did not have the required clearance and had to swap back to the original handguard.
Houston, we have a problem!
The Before sending the installed SupArms AR Piston Upgrade kit back to me, Tony called with concern over misaligned M4 feed ramp cuts on my Palmetto State Armory upper receiver. While I had not noticed any issues with ammo feeding before, I had only shot 55rg and 62gr FMJ rounds. Based on Tony’s observation and some research I ended up doing a bit of M4 cut clean-up with my dremel. Just very minor tweaks to the small cuts in the upper receiver to bring them in line with the feed ramps on the barrel extension. This appeared to correct the issue. When I switched to some fancy 75 gr Creedmoor Sports match ammo and found that the longer overall length of the bullet still snags on the transition area from the M4 cut to the barrel extension feed ramp. I will likely swap in a new upper receiver at some point.
This feed issue has absolutely nothing to do with the performance of the Superlative Arms AR Piston Upgrade kit. I mention only to highlight how thorough Tony at Superlative Arms was during installation and how the M4 cut issue with my upper receiver delayed our testing.
How did the Superlative Arms AR Piston Upgrade kit perform?
The goals of this upgrade and the results:
- Reduce the amount of carbon being blown back into the upper receiver, especially when being shot suppressed:
Success! There is still a bit of blowback that enters the chamber when the bolt retracts after a shot, but the bullet is already at, or very close to exiting the barrel by then (especially in mid length or rifle length gas systems). So, there isn’t much pressure left to drive gas back into the upper receiver area. This is really only a concern when a silencer is attached to the end of the barrel anyway. With the silencer attached I did not notice any blow-back after the AR15 DI Piston Upgrade Kit was installed. Click the following 2 pictures for larger images.
- Increase reliability:
It is too soon to positively comment on reliability. The SupArms AR Piston upgrade kit has performed flawlessly so far, but much more use will be required to give a meaningful assessment of longer term reliability.
- Allow for a wide range of ammo to be used reliably:
The “bleed off” gas piston system appears to handle any bullet weight just fine, whether suppressed or not. This is a big deal since most adjustable gas systems force you to choose one cartridge and configuration for when you set the gas block. Switching the bullet weight or moving from suppressed to unsuppressed can cause the system to be under or over gassed… causing operational problems. We will keep testing this system with various rounds and in a new upper receiver.
How Superlative Arms describes the AR15 Piston Upgrade Kit
“THE SUPERLATIVE ARMS PATENTED “BLEED OFF”, GAS PISTON SYSTEM FOR THE AR15 PLATFORM ADJUSTS THE GAS FLOW BY BLEEDING THE GAS OUT OF THE BLOCK INSTEAD OF RESTRICTING THE FLOW LIKE CONVENTIONAL ADJUSTABLE BLOCKS. RESULTS:
- The pressure used in the block is reduced only to the amount required to drive the bolt carrier. The remaining gas / pressure are bled out of the block allowing the system to run much cleaner and cooler.
- Reduction of felt recoil.
- Patent pending adjustment detent is located outside of the block and therefore no contamination.
- The gas adjustment screw does not restrict the gas flow; therefore there is no erosion or seizing of the screw / no loss of detent due to carbon build up. Although it is removable, we have added a safety mechanism, which stops you from unintentionally backing the screw all the way out.
- When using SBR’s and / or suppressors the bleed off port allows the excessive pressure to be exhausted out of the block reducing blow back.
- Firearm Type: AR15
- Gas Length: Mid
- Barrel Diameter: 0.625″
- Weight: 12.7 oz.
- Piston Block Attachment Type: Clamp On, Socket Head Cap Screws
- Piston Block Material and Finish: 416 SS, Melonite
- Carrier: Ion Bonded, 1 pc. Carrier w/ Skis and Dimpled Key
- Gas Adjustment: (Patent Pending) 30 Locked Positions, Front Of Block
- Bleed Off Port: (Patent) Front Of Block
- Piston Block Assembly
- Carrier (bolt not included).
- 3/32″ X 6″ Hex Key (tool to adjust gas screw)
- 9/64″ X 6″ Hex key (tool to install/remove gas block plug)
- Bushing and insert tool (Just an extra…. we have had some requests. Use at your discretion).
- Installation Instructions & QR Code For Video Tutorial”
More about the technical differences in DI and Piston AR systems
In a standard “Direct Impingement” (DI) AR15 the bolt pushes the cartridge into the chamber and locks it in place until the bullet fires. The bolt remains locked until a pulse of high pressure gas from behind the bullet bleeds into the gas block, down the gas tube, and into the gas key on the bolt, which forces the bolt carrier aft… causing the bolt to rotate and come unlocked so it can slide aft, removing and ejecting the spent round along the way. That is the 30,000 view of how the DI gas system works. It works pretty well for normal shooting, but has a drawback:
The high pressure gas is chock full of burned and unburned bits of carbon based nastiness when it vents into the gas key, then into the upper receiver. The carbon can build up and cause malfunctions. Plus, it makes a friggin’ mess.
Add a silencer to the mix, with increased gas pressure, and the mess gets worse. It can get so bad that someone shooting an AR15 with a silencer gets carbon laced gases pushed through the charging handle port directly onto their face, and potentially into their aiming eye.
A Piston AR system is similar to a DI system.
However, the gas tube is replaced by a solid rod which has a piston on one end. The is contained within the gas block where high pressure gasses from the gas port cause the piston to move. The solid rod impacts a flat on the top of the bolt carrier (where the gas key would be in a DI system), pushing the BCG aft. With no gas tube to dump carbon loaded gases in to the upper receiver, piston systems tend to run a lot cleaner. There is also no gas tube that can fail or sealing surface required between the gas tube and the gas key on the BCG.
If this system sounds familiar, it could be because you have seen other piston operated platforms like the AKM or SKS.
The SUPERLATIVE ARMS LLC – AR-15 ADJUSTABLE PISTON SYSTEM is a relatively simple and effective DIY upgrade that should be well within the capabilities of most AR15 owners. I really like that it is made in the U.S.A. While our test system operated flawlessly, it is nice to know that there is a 100% satisfaction guarantee along with Lifetime Returns. The “bleed off” gas system is rather unique and a big advantage over other system like the Adams Arms AR-15 GAS PISTON CONVERSION KIT, which has only an adjustable gas block which is not self regulating.
Dude! Where’d ya get that ammo?
The .223 Remington 55gr FMJ ammunition for this review was provided by Defender Ammunition Company. We also tried a few rounds of Creedmoor Sports 75gr OTM, but the max OAL rounds snagged on the malformed feed ramp extension prior to working my dremel magic.
About Superlative Arms
LLC. Is A Manufacturer Of High Quality Firearms Components. Their Background Consists Of Over Thirty Years Aerospace Engineering And Manufacturing. Our Patented and Patent Pending Ideas Have Been Fully Tested And Proven By The Industries Finest.
American owned, Middleton, Wisconsin based Vortex Optics designs, engineers, and distributes a complete line of premium binoculars, riflescopes, spotting scopes, tripods and related accessories. Dedicated to exceptional quality, value and unrivaled customer service, Vortex backs its products with its unconditional, transferable, lifetime VIP-warranty. Built on more than 20 years of experience in the optics industry, Vortex is rapidly emerging as a leading brand in the optics market. Vortex – The Force of Optics | www.vortexoptics.com
Defender Ammunition Company is named for and operated by veterans of the Armed Forces. In fact, 85% of Defender employees are proud Defenders of the country. As a company, we are loyal to our country as well, using USA-made products at every opportunity– from components to packaging. Defender Ammo Company is located in Raeford, NC, nearly bordering Fort Bragg.