November 2012

New AR-15 Rifles: Mossberg, Olympic Arms, Smith & Wesson

Mossberg’s MMR is a good entry, but we think Olympic Arms’ “Alphabet Gun” was overpriced. We’re glad that Smith & Wesson brought the versatile 300 Whisper to the M&P15 lineup.

Visit a public shooting range and it becomes apparent that the M16 platform has successfully made the transition from military weapon to serving the public as a means of recreation as well as home defense in the form of the AR-15 semi-automatic. Accordingly, model development for this platform continues apace, so in this article we’ll consider three new carbine-length AR-15s in 5.56mm NATO and 300 Whisper. Our first two AR-15s were chambered for 223 Remington or 5.56mm ammunition, by far the most popular calibers for the AR.

They were the Mossberg MMR Tactical Rifle (w/sights) and the Olympic Arms K3B-M4-TC-M4 Tactical Carbine, which Oly calls the “alphabet gun” for obvious reasons. Our third test gun is Smith & Wesson’s M&P15 300 Whisper, which stands out because it uses magazines interchangeable with the 223/5.56mm models but fires 30-caliber bullets. Our previous test of a 300 Whisper AR-15 featured a carbine directly from SSK Industries, the home of 300 Whisper’s inventor, J.D. Jones, ( The Smith & Wesson M&P15 300 Whisper is, to our knowledge, the first production model of this chambering from a high-volume major manufacturer. Mossberg is another volume manufacturer, but the MMR is the company’s first production-model AR-15.

To establish accuracy data, we visited the 100-yard range at Houston’s American Shooting Centers, ( To determine muzzle energy, we utilized an Oehler chronograph to measure velocity so we could enter it into the appropriate equation: Does computation of muzzle energy truly measure stopping power? Not necessarily, but it does provide a reliable indicator of the amount of force the projectile starts out with, just like MSRP (Manufacturer’s Suggested Retail Price) indicates possible retail pricing.

Test ammunition for our 223/5.56mm guns featured the three most popular bullet weights. We fired Sellier & Bellot 55-grain FMJ rounds, and two selections manufactured in Rapid City, South Dakota, by Black Hills Ammunition. They were the 60-grain V-Max and the 69-grain OTM. The Black Hills OTM (Open Tipped Match) rounds were marked 5.56mm NATO while the other rounds were designated 223 Remington. To test our Smith & Wesson rifle, we chose 208-grain Hornady A-Max and Hornady 110-grain V-Max 300 Whisper ammunition. Plus, we shot Remington 125-grain Accu-Tip rounds marked 300 AAC Blackout.

We should note that the use of names other than 300 Whisper was reportedly an attempt to avoid the expense of paying royalties to its inventor. This practice appears to be fading out. That Smith & Wesson lists 300 AAC Blackout only as a “co-chambering” but chose to designate this rifle as the M&P15 300 Whisper tells us that the Whisper name will win out.

Optics for our bench session consisted of the same Burris Xtreme Tactical 6-24X50mm with Mil-Dot reticle on each rifle (previously tested in our May 2011 issue). We also tried the new Brownells CQB T-Dot holographic sight by EOTech for offhand shots ($549, from This scope provided a hologram-style projection that offered a large circle surrounding a central dot for zero and a second dot for hold over to extend aim to additional points of elevation. The CQB T-Dot can be used as a standalone sight or in “co-witness” with iron sights. An outer shell provided impact protection and a quick-release mounting system. This type of sight is a popular add-on, and we wanted to know how our test guns would accommodate this system. Our team of test shooters included a highly ranked High Power competitor and a third generation United States Marine recently discharged and now serving in law enforcement. Let’s see how each of our AR-15s performed.

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