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June 21, 2011
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Dennis Haworth Firearms Training & Equipment
with Dennis Haworth

Product Review: GDI ACOG R-COM E-Model Combat Optic Mount

The R-COM comes in two variations, the B and the E models

In 1998, I bought my first Trijicon ACOG scope — a TA-11 with the “deadly donut” red circle reticle. My TA-11 served me very well on and off duty on my AR-15. Over the years I have used this scope through all the evolutions of my personal and issued patrol rifles — from fixed carry handles to flat tops. The same year I bought my ACOG, I purchased an A.R.M.S. #19 throw lever mount for it. At the time this was the best mount I could find that would allow me to quickly remove my ACOG and reattach it to the rifle and still maintain zero. My #19 has worked wonderfully for me over all these years.

During some recent testing I discovered that my #19 mount was not holding as tightly as I needed it to on some manufacturer’s rails. It holds solid on A.R.M.S. manufactured rails and most other brands, but on some it is too loose. This is most likely due to variations in manufacturing and tolerances between all the different companies now in the market as compared to the past. In any event, the issue remained the same: I needed a new mount for my TA-11 if I was going to be able to use it on as wide a variety of weapons as possible and that mount needed to be adjustable.

As I began my hunt for a new mount to deal with this issue, I found a product in the 2011 Tactical Assault Gear (TAG) catalog. It was an ACOG mount made by Global Defense Initiatives (GDI) called the R-COM. I looked up GDI’s web page and read up on the company and the R-COM. I learned that GDI was founded in 2002 and is a veteran owned small business out of Temecula, California. Originally, GDI provided security services and specialized training but they have grown to focus on the manufacturing of mounts for optics, lasers and other devices. The R-COM comes in two variations, the B and the E models. The B-model raises the height of the ACOG and allows the mount to extend over the top of a back up iron sight such as the Troy Industries BattleSight.

This allows more flexibility for eye relief when setting up the scope on the rifle. The Trijicon TA-31 ACOG has a shorter eye relief versus the TA-11 and other models. The R-COM B-Model would be my choice with short eye relief versions of the ACOG. The E-Model places the ACOG lower on the rifle, but when used with a backup iron sight the entire body of the mount must be placed in front of the backup sight. This places the ACOG further forward and reduces flexibility when it comes to eye relief. The TA-11 has a long eye relief so I opted for the E-Model to get the scope closer to the bore.

A Very Handy Kit
I contacted Kate from GDI and explained my situation. She sent an R-COM E-model out to me for a review. The R-COM arrived packaged in a very nice little, zippered, coyote-brown nylon pouch made by TAG. Inside the pouch was the R-COM E-Model mount, a small tube of Loctite 242, three screws to attach an ACOG to the mount, and a dummy corded laminated instruction sheet. This makes for a very handy kit that can be easily provided to a solder to upgrade to the R-COM mount. On inspection the mount itself appeared well made and very sturdy. I did not locate any machine marks in the CNC machined aluminum of the mount. The finish is MIL-SPEC type III hard coat anodizing in a uniform dark black. The locking arm and its components are large and appear to be very robust. GDI incorporated an Auto-Locking Quick Detach (ALQD) lever system.

This mechanism automatically locks the QD lever when closed. To release the QD lever the operator must pull back on the spring loaded thumb lock safety and rotate the QD lever away from the mount. The mount and optic can now be removed from the weapon. It is easy to do, but is a deliberate act and not something that is going to happen by accident. That is a good thing because you do not want your optic just falling off your weapon. The QD lever is located on the right side of the mount. I prefer this location as a right handed shooter because I do not like it when levers on my rifle get tangled up in my uniform or other kit. GDI states that the R-COM retains zero with repeatability at .01 MOA allowing the shooter to remove and remount the optic without loss of zero. As you’ll see later in this article, that was put to the test. The mount has four mounting holes for the ACOG allowing 3–3½ inches of adjustment in 3/8 inch increments to accommodate different eye relief needs.

On the underside of the mount where it attaches to the upper receiver or rail, the mount has a lug machined into the mount in front of the locking mechanism. This lug sits in the slot of the upper receiver or rail in front of the locking mechanism adjustment screw. GDI states that the locking mechanism consists of a non-abrading, non-gouging Picatinny rail locking feature that will not degrade the dimensional integrity of Picatinny rails. It is capable of adjusting to worn or out-of-spec rails by tightening or loosening the QD lever adjustment screw.

I installed my TA-11 into the R-COM and secured it to the mount with two screws. Following the instructions that came with the R-COM, I installed the mount and optic on the upper receiver of my M4. I found that with my Troy BattleSight installed on the rear of the upper receiver I could install the R-COM so that the rear of the mount almost touched the front of the folded iron sight with the rear of the ACOG extending over the top of the Troy sight. With a standard four position M4 stock extended to the second position this placed the TA-11 exactly where I wanted it.

Range Testing
For me, when using an LMT SOPMOD stock, I like the stock completely collapsed. With this stock I preferred to place the R-COM one position forward on the upper leaving a small gap between the R-COM and the Troy to get proper eye relief. This is how I conducted all range testing of the R-COM.

Once mounted, I discovered that when using my Laser Devices DBAL-I2 the R-COM E model placed my ACOG too low. The DBAL-I2 obstructed too much of the lower portion of the optic. I was able to use my Laser Devices OTAL with the E model, but from this I would chose to use the B model in conjunction with any laser system or any other kit placed on top of the rail forward of the optic.

At the range I sighted in my ACOG at 100 yards. At 50 yards began removing the sight, manipulating the locking arm three to five times, reattaching the scope to the rifle, and firing two to three rounds each time. I attached the mount at the same location on the rail each time I reinstalled it for consistency. Periodically I would strike the side of the ACOG with the palm of my hand on the left or right side. I did this approximately 20 times and then went to check my target. I discovered that the 50 rounds I had fired were in a nice consistent group. The mount had held zero. I repeated this cycle on other targets at 75 and 100 yards and found no loss of zero during testing.

I attempted to adjust the tension screw in the field using a military issue Gerber multi-tool. This was unsuccessful. I examined the screw closer and it appeared that it was red Loctited to the lever. I contacted GDI and asked about this issue. I was informed that their mounts do not use Loctite during assembly. The adjustment screw has significant resistance to provide for positive retention. It is important to understand this when making adjustments to the screw and you must use a properly sized slot screwdriver. I highly recommend following the directions when making any adjustments. GDI adjusts their mounts to fit in-spec M1913 rails during final assembly at the factory.

Most users will not have to make adjustments to the mount unless the rail they are using is out of spec. The mount can be adjusted using either of two methods. The recommend method is done with the optic dismounted from the rail for initial adjustment. Once you have completed this, you can adjust the mount with either method. When mounted on the rail, GDI recommends opening the lever forward, away from the shooter, to the one o’clock position. Once opened, using a properly sized slot screwdriver, the adjustment screw can be turned clock or counterclockwise. GDI recommends micro adjustments of 1/16th to 1/8th turns until desired tension is attained.

Very Good Results
For making subsequent adjustments, you can use the mounted to the rail method. The lever can be closed in the locked position during adjustment. Again, using a properly sized slot screwdriver, the adjustment screw can be adjusted clock or counterclockwise until desired tension is attained. Which either method is used, I highly recommend that you take your time and go slow as the amount of adjustment will vary depending on the tolerances of the rail system.

At the end of testing I can say that I am very happy with this mount. The tension adjustments are not as easy as some other designs but this can be a good thing on issued equipment. Users who are not as knowledgeable to the particulars of how to properly adjust their mounts will have a difficult time of playing with the mount and inadvertently damage something. The mount is well made and built to last. The locking arm is large and can be easily manipulated when wearing gloves.

The ability to rapidly remove the optic is important on a combat rifle. If the optic is damaged or obstructed in some way you will want to employ your back up iron sights. To do this you may need to remove the optic to get it out of the way to be able to aim the rifle. When using magnified optics this is most likely going to be the case. If this situation occurs at work you’re probably going to be under stress and involved in some kind of violent encounter. The large locking lever and release button make this quicker and easier than smaller control surfaces. Best of all it held zero, attesting to the quality of manufacturing of GDI. I look forward to future products from this company.

About the author

Dennis Haworth is a police officer with a California state law enforcement agency. He has been a law enforcement range master and armorer for more than a decade. Haworth has served as a police academy instructor and has taught specialized courses on several subject matters. He has been involved in product testing for professional associations, manufacturers and law enforcement agencies. He has a BS in Criminology and an MPA with a specialization in human resources management. Much of his free time is spent as an advisor to the Shooting Sports Club at his local University of California campus.

Contact Dennis Haworth

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