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Tactical AR-15 Rifles

NEMO Omen .300 Win. Mag. Review

by Patrick Sweeney   |  August 19th, 2013   |   15

In the 1980s, I was delving deep into all things AR. I was shooting them in the first 3-Gun matches, building them up and repairing the home-built Frankenguns my customers would bring in. I was also experimenting. I had worked out a number of caliber conversions for the AR and even considered what it would take to turn the early AR-10, a fragile and rare rifle, into a reliable one. Never in my wildest dreams did I think to build one in .300 Winchester Magnum.

All that passed through my mind when the guys at NEMO handed me their Recon rifle at one of our company’s editorial Roundtables. Hmm, some could say it is a tad portly, but then again, who wants an airweight .300 Win. Mag.? The controls were in the right places, and I liked the fact that NEMO was handing me one that had the camo finish all scuffed and worn. Clearly, this was no toolroom R&D orchid, but a working rifle that was expected to get shot hard and hung up wet. And it had a muzzlebrake on it.

Again, I would consider a brake on anything chambered in .300 Mag. to be de rigeur.

“The muzzlebrake is our own design, and it really decreases recoil,” says NEMO. I looked at the brake and the roof over our heads. I stepped forward as I shouldered the rifle to make sure I had the brake out past the eaves and, planting the crosshairs on a plate, touched it off. Not bad at all. I turned to the NEMO guys and asked, “How soon can you send me one?”

If I said the Recon they sent me was very interesting, you’d think I was bored. No, it intrigued me in a way I haven’t felt in a long time. The controls and the parts you hold on to are all bog-standard AR-type parts, or sized as .223/5.56 parts. The stock is a Magpul STR on a Mil-Spec tube (with a properly staked castle nut), so if you don’t like the stock, you can change it. The pistol grip is a Hogue; ditto on changing it. The safety and trigger are right where you’d expect them to be, and the handguard is refreshingly slim, especially for a rifle chambered in .300 Win. Mag.

The forearm on the Recon is particularly slim, as it is octagonal and no larger than it needs to be. While it has a rail along the full length of the top, the sides are bare save for threaded screw holes. Want a section of rail for a light, laser or bipod? Bolt one on. The rest stays bare and slim. The rifle came with two short sections of rail on it, so there would be a chance to attach a bipod or illumination tool if I so desired. The forearm free-floats the barrel, plus it is anchored to the upper receiver. Not only does it clamp on the barrel nut, the forearm has two anchor screws, 90 degrees to one another, fastening the handguard to the upper receiver.

The really interesting parts are the middle and the muzzle. The receivers are large. No, I mean large. The upper has a Picatinny rail along its length, flush and even with the rail on the handguard. You could bolt more gear up there than you could pick up, so show some restraint. The lower has a magazine well proportioned to accept the proprietary .300 Win. Mag.-size magazines, and the edges of it are scaled up as well. It is big, but you don’t get the impression that this is an anvil, it’s just really muscular.

The bolt and carrier are obviously scaled up from even a .308 rifle, and the nickel-boron-coated carrier has an interesting detail: The charging handle is attached directly to the carrier — no top-center charging handle flimsily fabricated from aluminum. Instead there’s a hefty handle to hang on to.

Plus, the billet-cut receivers are done in NEMO’s Tango pattern, a brushed-stripe, black-and-bronze-camo anodized, not painted, finish. Inside the lower we have a Geissele two-stage trigger.

The gas port is covered by a low-profile gas block that has an adjustable gas-flow knob on its front face. Out in front of that is the muzzlebrake, a multiport one clearly designed to take the steam out of recoil.

A long-range rifle needs suitable optics, and I had just the hunk of glass on hand to fit: a Nightforce 5-25x56mm ATACR and their MIL-R reticle, complete with a selection of Nightforce rings to choose from. The 5-25X is an impressive assembly of optical engineering, but to get the kind of performance it delivers, you pay for it. Not just in cost, although I find I have to keep telling the little voice in my head that I’m not paying for this gear in 1982 dollars anymore. After buying proper, professional lenses for my DSLR camera, I’m not as startled at the price for good firearms optics. No, the big price is in weight. Glass weighs a lot. In fact, glass can be three to seven times as dense as water, with optical glass not being near the bottom of that scale.

The Nightforce ultralight rings use hefty bolts to clamp down on the Picatinny rail, and the nuts on them require a half-inch open-end wrench or socket wrench to tighten. You want them tight, but you don’t want to be crushing your receiver, tightening your scope rings with power.

Mounting optics such as this to a regular rifle, I’d be just a bit embarrassed. I mean, a 21/2-pound scope, in nuke-proof rings that add more than just a couple of ounces? On a proper-weight M4, that would be a bit silly, but the NEMO Recon tips the scales, absolutely bare, at 10 pounds, 9 ounces. With the Nightforce scope and rings, a sling and a loaded magazine, the Recon comes up to just shy of 15 pounds. Keep in mind, this is a .300 Winchester Magnum, and even with an efficient muzzlebrake, weight is your friend in dealing with recoil.

One small problem I had in getting everything at the range to test this rifle was ammo. It’s not that I couldn’t find any, but that I didn’t have any. Once I got home from the InterMedia Roundtable, I checked the ammo shelf. I had one lone box of .300 Win. Mag., a box so old that the price on it was less than $10. I had no memory of how I’d come to acquire it, since I’ve never owned a rifle in this chamber before. I jumped on the phone to beg .300 Win. Mag. ammo from those who have it. Interestingly, a lot of ammo makers list it, but mostly for hunting.

In the AR universe, ammo companies have long been hip to where their ammo is used. Everyone who loads .223 has a pretty good idea that it will end up in one of the host of ARs out there on ranges around the country, so they load accordingly. Well, no one who loads .300 has had any idea that there would be an AR-based rifle chambered for it. The most they’d expect is that some hunter with a Browning BAR would use their ammo, and so what? The NEMO engineers had to make their gas system work with the ammo as it existed, not just on specially tuned handloads, thus the adjustable gas-flow knob. The one-dot setting is the suppressor setting, and Gemtech makes a special Sandstorm (titanium) model just for this caliber. Four dots is wide open and more gas than you probably need.

The magazines for the Recon are made of polymer, and, as you’d expect from magazines that will accept .300 Win. Mag., they are hefty. If, when I began my AR journey, you had suggested that someone would be offering a fabulously expensive AR and shipping “plastic” magazines with it, I would have laughed. In size, shape and general appearance, they remind me of the magazines for a Dragunov, but even bigger. Until the web-gear guys start making NEMO-specific pouches for us, you may have some trouble packing along extras.

At 14 rounds per mag, you are not going to be getting long strings of fire from this, but then that isn’t what it’s for. The basic idea that NEMO has for the Omen line of .300 Winchester Magnum rifles is long-range precision fire to support or replace bigger-than-7.62 bolt-action rifles in the sniper role. This is not the rifle you’d want to be using in an urban slugfest, unless it was all you had. No, the NEMO .300 Omen lineup (the Recon is just the handiest of the models so far) is meant for long-range bad-guy whacking, and you could expand that a bit to close- and medium-range heavy-hitting. After all, a .308 fires a 175-grain match bullet at around 2,600 fps from a 20- or 22-inch barrel. The .300 Win. Mag. promises to best that by 300 fps and with a bullet heavier by 20 grains or more. Higher velocity and better ballistic coefficient means better long-range results. However, with real heavyweights, such as a 200-grain Trophy Bonded Bear Claw, auto glass and other barriers become pretty flimsy protection for would-be miscreants. The handy-length, 18-inch barrel takes a bit of the extra speed away from the big .300, but not much.

I started by setting the gas regulator to the low setting and worked my way up. I gauged proper gas settings by how far the brass was hurled. It was easy to set the regulator to keep from trashing brass. At the lowest setting, it flipped the empties about 7 or 8 feet away. At the highest setting, 15, I discovered an interesting problem: The muzzlebrake was too good with some loads. With the low-vigor gas-blasting loads, the muzzle stayed on my mark while I was doing my chronograph work. The heavier-bullet loads had the sights actually pushed down off the target from gas flow through the brake. I could also gauge pretty closely how well I was maintaining my offhand stance; as I got tired, the muzzle started driving off to the right as well as down.

You can’t get something for nothing. A muzzlebrake that is that effective is going to blast everything in its path. I tried a few strings from prone, but the autumn litter erupted into clouds of scurrying leaves on each shot. If you are going to be using this for real, you’ll want to have a solution in mind for the muzzlebrake and its effect on your environment. That said, the felt recoil was pretty soft.

NEMO also built in a spring-loaded plunger in the rear of the carrier. When the carrier and buffer weight bottom out, the spring-loaded plunger soaks up the last bit of energy, eliminating that bottoming-out bounce that hard-kicking self-loading rifles often have. I don’t like comparing it with other calibers, as we all have our own ideas of what a .243 or a .30-’06 feels like, but the NEMO Recon is a softie to shoot. I did not come away from a range session with a sore shoulder for the price of fun.

Shooting the NEMO Recon is work, it just isn’t work to shoot it the way other rifles are work. The rifle, full up, is heavy. That’s the price you pay for soft recoil and the power of .300 Win. Mag. The muzzlebrake is efficient, but you cannot have anything on the firing line with you; it will get blown off.

The .300 Win. Mag. is a barrel-heater. Sluicing that much burning powder down the bore on each shot, I found I had to break my bench-testing routine into sets of four five-shot groups and not at anything like a fast pace, then walk down, measure, tape and reset while the barrel cooled. Any faster and the groups opened up. Not a lot, but given the brilliant accuracy of this rifle, you do not want groups opening up. When I kept my cool and the barrel cool, I could punch sub-MOA groups.

I had figured that something this radical, this edge-of-the-envelope, would have problems. I expected to see malfunctions, mangled brass, ammo bent and dented by misfeeds. I may as well have saved myself the time spent anticipating problems, for it worked without a flaw.

I’m of the opinion that this rifle is a better shooter than I am. I’ve never had the benefit of a rigorous benchrest education, and my bench-and-bag technique is not at as high a level as my high-speed skills are. I was stunned to see quarter-inch groups. I have to give all the credit to the rifle, scope and ammo, as I was pretty much along for the ride. If you have access to a long-distance range, you really ought to give a thought to how you are going to spend your trigger time. Spending it with a NEMO Omen, this Recon or any of the company’s other rifles would not be a bad day.


Look for the NEMO Omen in Book of the AR-15, a publication dedicated to all rifles, optics, and ammunition engineered for the AR-15 platform. Order your copy at the InterMedia Outdoors Store today!

  • 48woody

    I love the .300 WinMag cartrige. That is a pretty big AR platform, in this article. How hard would it have been to adapt an M14 to that cartrige? I carried an M14 in the late ’60′s and I loved that rifle. Set that action and barrel in some modern military “furniture” and voila.

  • Bill Tallant

    Great, detailed technical write-up, thank you. The video says the MSRP is $5900, and I’m sure it’s worth it for someone who wants the ultimate AR, but the only advantage over a much less expensive and equally good quality BAR in this cartridge is the magazine capacity. I think I’ll look into a good quality hi-cap .308 auto-loader instead and call it a day, as I don’t have that kind of dinero unfortunately. (I also think NEMO is missing a bet if they don’t take this great collapsible bolt carrier system and design it into a 7.62X51 platform. They would instantly triple their potential market, and have a softer shooting rifle than any AR-10 out there!) Thanks again for a neat article.

  • BJC

    Looks like a hell of a nice rifle. The only thing I didn’t like was the price 6K is way out of line.

  • BDC

    So, its a magnum with no ballistics and lots of extra unburnt powder. al. Wait not only did you waste the ballistics of a magnum cartridge with the 22″ barrel , you doubled-down for an 18″ version. I would be curious to 1. See the drop in ballistics, nullifying most likely the magnum cartridge advantage. 2. The amount of unburnt powder getting pumped into the gas system. Even 24″ barrels in magnum cartridges are essentially a waste. I shoot all of mine in a minimun 26″, some even in 28″ to get the true velocity and dare I say ” efficiency” ( which magnums are not) out of the magnum caartridge. And being we are starting this conversation at 1,000 y/m since the 7.62 is now out, who needs semi auto rapid fire past 1,000 yards? I would then be looking at other options, especially for $6,000. 50bmg, 416 cheytac. Obviously, money isnt an issue for Military and police , sooo.

    Didnt armalite already produce a .300 short mag AR version years ago? Being that it mimics the .300 win mag ballistics, I dont see the point. Kudos for the bolt design, put it in other common, practical calibers and sell a million.

    I dont rally see the benefit to the hunter here also. Rapid fire elk at 6,7, 1,000 yards?
    More effective, efficient rounds are 6.5×284, 6.5 creedmor, .260 rem put those in 18-22″ barrel semi-auto platforms. Yes they all exceed 7.62 ballistics at long range, etc…etc…etc…more american hubris.

    • load

      300 wm achieves a full burn of 76 grains of powder under 230 grain bergers in a 22″ barrel. the same goes for 69 grains imr 4350 and 178 grain amax. I is true that a longer barrel will give you more velocity but only around 30 fps per inch from 22 to 26 inches. above 26″ you only gain around 15 fps to 30″. this is a function of pressure not unburnt powder. your barrel harmonics moment of angle in exponentially increased with increased length. The military has tested all of this and settled on 22″ barrels for the 300 win mag cartridge.

      • load

        76 grains h1000

  • SamF1911

    What, no chronograph numbers?

  • DeltaZulu

    Hell, if you think an AR in .300WM is impressive, check out Noreen’s Bad News in .338 Lapua Magnum…. Oh, and by the way, it also comes chambered in .338 Norma and, wait a minute, .300 Winchester Magnum! Guess the Omen isn’t the only AR in .300 WM, or the first, as Noreen has been making these for several years now.

  • NOYFB

    The article says the rifle came with a flash hider and not a muzzle brake, but that most certainly is a muzzle brake on the rifle.

  • KPO

    Love to see you guys do a comparison with the Miller Precision Arms 300 Guardian… They also claim to be the first 300 win Mag, but they say it is in a true AR platform!

  • dwpittelli

    Why would anyone pick this over an AR in .260 Remington? (I mean, unless you have to penetrate light armor or something.) Same trajectory, cheaper rifle, cheaper ammo, shorter action, lighter rifle, less recoil and less muzzle blast.

    • Tucson_Jim

      Retained energy for enhanced “Maximum Effective Range”… .as stated in the article, the .308 Winch/NATO 7/62 as commonly used for sniper work: “…175-grain Sierra MatchKing bullets… …depending on which branch of service you talk to, are effective out to 800 meters (according to the U.S. Army Special Forces) or 1,000 yards (according to the Marine Corps).

      The 300 Win Mag adds approximately 200 – 300 yards of kill zone. While the .260 Remmy is a flat-shooting round about perfectly suited for ranges from close-quarters out to normal combat ranges of 500 yards, but, is a lighter round and more susceptible to cross-wind. It is a serious improvement over the rat-shooter 5.56mm round, but, weights appreciably more too… Still, it is inadequate for intermediate to long-range small arms work.

      The next range beyond 300 Win Mag is filled by the .338 Lapua Magnum (used by Chris Kyle to kill an insurgent with a rocket launcher at 1,920 m (2,100 yd)), Which is then followed by the .50 BAR, and good out to 2000 meters.

    • Unlicensed Dremel

      Amen and hear hear – you nailed it – other than as a tool for 1%ers to make sure they turn MORE money into noise than the rest of us – with more boom, more weight.

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