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one417
01-17-2010, 11:10 AM
After selling my gas piston upper (POF) last year, I decided to look in to another gas piston system in 2009. I had an opportunity to fire a LWRC. It seemed to be the rockstar of gas pistons at the time. As I researched and compared gas piston systems, a small, local (Southern California) company caught my eye. ADDAX built gas piston uppers based on the PWS design. I then decided to call them for more information. Chris (owner of ADDAX) took about 45 minutes of his time to answer all my questions and educated me on the gas piston system during our first phone conversation. I appreciated the time he took to talk to me, not knowing that I would ultimately purchase one of his uppers. After reading more about ADDAX, I decided to take a chance on a company operating deep in the heart of enemy territory - California, specifically within the City of L.A.

I've had the ADDAX ATAC-GPU for a little over four months now. After about 5000 rounds fired through the system (including a Magpul course) , I thought that it was time to write my review on the upper. I purchased the upper from Chris at ADDAX as SPEC'd below with the addition of a set of Magpul MBUS sights. Prior to it's first range day, an Aimpoint T1, Magpul XTM rail panels, TD Stubby VFG and a weapon light were added. It has stayed in that configuration but mounted on numerous brand lowers to check fit and function.

The ADDAX ATAC GPU was SPEC'd as follows:

THE ADDAX GPU MK1, 16" MILITARY SPEC. 5.56 MODEL

-PRIMARY WEAPONS SYSTEMS LONG STROKE PISTON SYSTEM

-DANIEL DEFENSE COLD HAMMER FORGED MIL-SPEC 16" CARBINE 1:7 TWIST CHROME LINED M4 PROFILE BARREL

-MICROSLICKED* MIL-SPEC FULL AUTO BOLT CARRIER GROUP

-ADDAX FSC BULLDOG COMPENSATOR

-PWS LONG STROKE CARBINE GAS PISTON SYSTEM (BASED ON THE PWS DIABLO SERIES).

Long Stroke Piston System
Specially Designed Gas Block (Pinned to the Barrel)
Piston Design Enhances Dwell Time
All piston parts are finished in Melonite QPQ for Improved Wear Resistance, Heat Resistance, and Enhanced Corrosion Resistance.

-MIL-SPEC A4 7075 T-6 FLAT TOP UPPER RECEIVER WITH M4 RAMPS

-16" DANIEL DEFENSE M4 COLD HAMMER FORGED 1:7 TWIST (4150 CHROME MOLY VANADIUM STEEL) CHROME LINED CARBINE BARREL WITH M4 FEED RAMPS, MP TESTED, FULL AUTO RATED

-LOW PROFILE QUAD RAIL SYSTEM WITH 3 INTEGRAL QUICK DISCONNECT SWIVEL MOUNTS

The rail system consists of 4 individual rail panels mounted to a specially designed trunnion and mounting system.
The Gas Block sits under the rail, allowing the upper to have a slim profile.

-MAGPUL XTM RAIL PANELS (BLACK) FOR THE SIDE AND BOTTOM RAILS

-MIL-SPEC FULL AUTO BOLT CARRIER GROUP WITH MP TESTED BOLT

-BOLT CARRIER GROUP FINISHED WITH MICROSLICK

*Cerakote Micro Slick is a (dry) film lubricant coating that assists in reducing friction and wear, and can withstand extreme pressures and temperatures.

During use, the Ceramic properties of the Microslick surface treatment are mashed and polished into the pours of the metal on the contact surfaces,
which allows the action to cycle smoothly, imparting a semi-self lubricating quality to the bolt carrier group.

-MIL-SPEC CHARGING HANDLE

-FSC BULLDOG COMPENSATOR

My experience with other AR platforms owned or Department issued are limited to the following: Various agency Colts (20" rifles, Sporters, M4's), Colt 6920, Armalite (sold), POF gas piston (sold), LMT (14.5' & 16"), BCM Mid-lengths (love them, have 2), Custom 18" JP.

When the upper was first picked up, I was excited and couldn't wait for a range day.....but then again, I got excited about every other upper that I bought. The ADDAX appeared to be solidly built and well finished.

The first time shooting the ADDAX GPU was definitely a satisfying experience (satisfied that my new purchase worked with no issues). I was told that it shot or "felt different" from any of my previously experienced DI uppers as well as my early model POF. It did feel a little different with a slightly sharper recoil that the DI uppers, but with the FSC Bull Dog comp, it's recoil (i felt) was better managed than my other uppers and flash hiders (A2 Birdcage, Vortex).

My first session included a 50yrd BZO, followed by some drills inside of 25 yards. Day one concluded with about 300 rounds (Win Ranger 55gr Pointed Soft Point) fired without any malfunctions. The ADDAX GPU was fired as it was delivered, lubed by the manufacturer. The magazines used during day one were, Colt G.I., Pmags, TD ARC, and Lancers. They all worked well. After day one, I stayed with my preferred Pmags.

An observation made during my first day's drills were that the top rail definitely got HOT. Three sides of the GPU's rail were covered with XTM panels. I was told by Chris to leave the top rail uncovered to aid in dissipating heat. The only thing on the top rail was the MBUS front sight mounted forward of the gas block. To date, the heat has not affected the polymer sight at all.

Gloves are probably a must (I usually wear gloves when training with AR's) is you don't want to get burned. As advertised, the BCG remained cooler than the DI guns. Another observation was that the FSC Bull Dog rocked! It is a little louder than the A2's but perform better in controlling muzzle rise, thus aiding in faster follow up shots for me. (On a side note: One of my BCM Middys now have the FSC Bull dog and plan on getting it on others). Although I have limited experience with the various flash hiders and compensators in the market, I really liked the FSC Bull Dog.

I disassembled the weapon for inspection after the first session. The BCG and Op-Rod are attached and link with the CH, so the whole unit has to be taken out of the upper assembly.

However, it was just as easy as dis-assembling a conventional DI upper. The BCG as well as the attached Op-Rod appeared fairly clean. A quick look in the buffer tube showed no noticeable signs of wear (from the dreaded bolt carrier tilt issue). The BCG assembly with the attached Op-rod is designed to minimize carrier wear as well as carrier deflection/tilt.

So far - so good. I didn't clean the upper, however, Slip 2000 was added. I know, gas pistons are supposed to run even when dry, but (lubing) habits die hard. Re-assembling the system was also simple. First, line up the the Op-Rod with the gas tube, drop the CH in it's channel followed by the BCG.

For the next three months, I used the ADDAX GPU during range training sessions. I had two malfunctions that I attributed to one of my training aluminum G.I. mags with green followers. After marking and putting the offender magazines away, I experienced no more malfunctions. The upper performed admirably and better that I originally expected. I did not clean the upper but kept the BCG lubed with Slip 2000 after each ~ 1K rounds fired.

During the second week of December, I hosted a 4-day Magpul hydrid HVWM/Advanced Carbine course for my agency. I thought that this course would work the ADDAX GPU and bring out any issues with my rifle. The training days' weather were mixed with cold (lower 30's) days and rain on day 4. One of my team member's department issued rifle took a dump early. I loaned him one of my BCM's, but he also wanted to shoot the GPU. He ended up with the GPU for the last two days of class. Our experience with my ADDAX was that it was a solid performer through the whole course with NO malfuctions.

The upper was not babied in any way. It was used in all the drills the the Magpul instructors set up. There were 24 shooters, with three shooting gas piston systems. There were two ADDAX GPU's and one LMT GPU. Another team member also using his ADDAX GPU throughout the experienced ZERO malfunctions with his upper. There were several weapon maufunctions (ammo, magazine, and extractor related) experienced by other shooters. The two ADAX GPU's in the class functioned flawlessly!

After the Magpul course, I decided to disassemble the upper for a thorough wipe down because of the previous day's training in the rain. The BCG was fairly clean. All it required was a quick wipe with a rag. The gas piston Op-Rod had some carbon build up on it. A spray of Slip 2000 Carbon Cleaner aided in easily wiping the carbon deposit off. I ran a Boresnake through a few times, thoroughly wiped down the exterior, and called it a day

I am extremely satisfied with the performance of my ADDAX GPU and look forward to many training sessions with it. Thanks to Chris at ADDAX Tactical for doing a great job on the build!

Addax
01-24-2010, 12:48 PM
Thank you for the Excellent Review.:D

69Mach1
01-24-2010, 1:08 PM
Outstanding review and upper.

supermario
01-25-2010, 12:15 AM
Yeah cool, that ATAC would be nice mounted on a LMT Defender with sopmod stock..

Addax
02-06-2010, 11:31 AM
Here are some pics (same review but from a different forum):

http://i2.photobucket.com/albums/y21/One417/DSC00725.jpg


http://i2.photobucket.com/albums/y21/One417/DSC00839.jpg



http://i2.photobucket.com/albums/y21/One417/DSC00705.jpg
http://i2.photobucket.com/albums/y21/One417/DSC00697.jpg
http://i2.photobucket.com/albums/y21/One417/HPIM1859.jpg