By Joe W Gorman
Since 1996, Rock River Arms (RRA) has been producing quality firearms for shooters, the US, and foreign governments. RRA earned a well-deserved reputation as a manufacturer of top-quality AR-pattern rifles, in a multitude of calibers, at reasonable prices. Currently based in Colona, IL, RRA also manufactures 1911 pistols and rifle accessories.
RRA makes an AR-15A4 NM rifle featuring a heavy stainless barrel resting inside a free-float tube, covered by A2 handguards. I remember the A2 versions of these NM rifles appearing in the 90s and I was always drawn to their looks and the results of their use in the hands of match shooters. I never owned one.
I requested a NM A4 Upper (AR0790B) from RRA to evaluate its potential for varmint use out west. I have a dedicated HBAR Colt that serves as a medium-range varminter and a Ruger M77II Varmint bolt rifle with a 26” barrel that has killed prairie dogs beyond 400 yards with 50 grain ammunition. My evaluation of the RRA NM A4 upper was to assess its suitability to replace my 26” Ruger bolt gun so that my pack out for prairie dog hunting would be a hyper accurate AR with a medium power scope, my trusty Colt A4 with 4x ACOG, a Custom Shop Ruger 10/22 (that has a confirmed kill at 360 yards. Yes, I have witnesses) and a 6.5 Creedmoor Ruger Precision Rifle that can hit prairie dogs at 825 yards. To replace my bolt gun in the field, I thought the upper must be capable of ¾” groups or less at 100 yards with match and varmint ammunition. The thought is, with light varmint ammo, the upper should be capable of hits to 400 yards, and with heavy match ammo, capable of hits to 600 yards. I realize that is mighty ambitious for an AR chambered in .223 when shooting such small targets.
RRA’s NM A4 Upper with precision front sight
RRA’s NM A4 Upper features an air-gauged, stainless, 20-inch, heavy-barrel with a 1/8 twist and a Wylde chamber to permit shooting .223 and 5.56mm ammunition. Under the handguard the barrel is .95” thick! As previously mentioned, the barrel is free floated via a steel sleeve that does not contact the front sight but permits traditional installation of AR plastic handguards. This makes the NM A4 Upper appear to be, merely, a heavy-barreled A4 upper, but the stainless barrel indicates this is an old-school match setup. I figure, I break this out at the range while the young guys snicker “OK Boomer!” under their breath. The NM A4 Upper comes with a charging handle and a mil-spec, chrome-lined bolt carrier and bolt carrier group. It fit on top of my Colt lower without any issue. Fit, finish and overall appearance of the RRA NM A4 was first-rate. The machining of the chamber, the finishing of the feed ramps and the finish of the upper all looked extremely precise and well executed.
RRA’s stainless heavy barrel proved to be one great barrel
Moving to the range portion of the evaluation, I fitted Leupold’s excellent, new Mark 4HD 2.5-10x (Illuminated TMR M5C3 FFP) scope in a rock-solid Leupold Mark AR 30mm mount to the Colt/RRA rifle. This rig tipped the scales at 11lbs, 9oz. Not something an infantryman would want to carry all day, but exactly the kind of weight a varmint hunter wants when he’s looking for a rifle to park on a hilltop. When trying to make extremely precise long-distance shots on rat-sized, grass-powered targets, this varmint hunter appreciates inertia. I also need to mention the Timney drop-in, Competition AR trigger that drops the pull weight to 3 crisp pounds. This awesome drop-in trigger allowed me to squeeze all the potential out of this rifle system. I’ve used in on my Colt A4 for a couple of years now and it’s rock solid. It took me all of 5 minutes to install and it’s been flawless ever since.
Timney’s competition AR trigger is a big part of the rifle accuracy equation
A few words about the scope; I have been a Leupold fan since looking through a friend’s variable-power Leupold scope in 1985. The new Mark 4HD from Leupold is the latest in the storied Mark 4 tactical scope line, that goes back to the 1980s. This latest Mark HD, features user adjustable reticle illumination with motion sensor technology (turns on when it moves, and it turns off when it’s been sitting for 5 minutes), a zero lock (which EVERY tactical scope should have, I mean, at least according to me), 1/10th MIL turrets, 28.7 MIL of turret elevation travel, fog proof and shock proof construction and AMAZINGLY clear glass, particularly after legal sunset. And when I say “amazing” I mean when comparing other scopes at that price point, the new Mark 4HD is the Heavyweight Champion of the World at this to my eye. No, seriously, if you’re going to drop a $1000 on a tactical scope, please don’t buy one until you look though this new Mark 4HD. The Mark 4 HD allowed clear sighting in various light conditions for this testing.
RRA’s NM A4 Upper on author’s Colt lower with Leupold’s new Mark4HD FFP glass in Leupold Mark AR 30mm mount.
As mentioned earlier, this rifle system has mass! Resting on a Harris, S-BRM bipod (with a Harris No.5 adapter) the rifle was incredibly stable. Careful as I was with breathing and pressing the trigger, I was rewarded with incredibly consistent groupings from many different types of ammunition. Much to my delight, my favorite varmint ammo types shot well. Hornady’s 55gr .223 VMAX and Fiocchi’s 50gr .223 VMAX both shot sub-1/2” groups at 100 yards. Two flavors of match ammunition, Hornady’s 75gr Superformance Match and 73gr ELD Match, both turned in nearly 3/4” 5-shot groups at 100 yards!
Hornady’s 75gr Superformance Ammunition is serious medicine. It’s very accurate.
Hornady’s 55gr VMAX ammunition grouped well from the RRA NM A4 upper
After every 40-50 rounds, I stripped the rifle down and ran a couple patches soaked with Hoppe’s Copper solvent on a jag through the barrel with a Dewey coated rod and jag, guided by a Dewey chamber bore guide to ensure the rod stayed on axis with the bore. I followed this up with a bronze brush (only pushed through the bore and removed before I pulled the rod back out) and clean cotton patches. I’m not sure what the bench rest crowd would think of this protocol, but my group sizes remained tight. I also thoroughly cleaned the bolt carrier group too, just because I like testing with a clean rifle. Over the course of testing, I shot more than 300 rounds and experienced no malfunctions.
Fiocchi’s 50gr VMAX Ammunition turned in the tightest 3 shot group!
As the table below shows, this is one crazy-accurate AR15 upper! In fact, this is the most accurate AR15 I’ve ever shot. Using the Hornady Superformance Match 75grs, I can almost equal the velocity I could get with Hornady Match 75gr ammunition from my Ruger bolt gun. While the bolt gun still holds a slight edge in accuracy it sure isn’t by much. This makes my plan of 2 ARs covering my 5.56/.223 needs out west on varmint hunts a reality. RRA makes an incredible NM A4 Upper for those searching for such a beast. I’ll be looking at more RRA products in the future!
Hornady’s 73gr ELD Match is a great round
| Ammo | Avg Velocity | Best 3 shot group |
| Hornady 55gr VMAX | 3055fps | .40” |
| Hornady 73gr ELD Match | 2780fps | .42” |
| Hornady 75gr Match | 2690fps | .49” |
| Hornady Superformance 75gr Match | 2815fps | .57” |
| Fiocchi 50gr VMAX | 3155fps | .33” |
Contact: Rockriverarms.com
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