MPR 308/5.56 Offers Multiple Calibers On One Platform

The Olympic Arms MPR 308/5.56 seamlessly jumps between AR-10 and AR-15, giving shooters a ton of caliber choices. Leap from tactical carbine to heavy deer gun in an instant.

It’s safe to say Olympic Arms has a knack for innovation.

The Washington-based gun maker cooked up some of the first pistol-caliber ARs. It introduced the flat-top upper receiver. And it has generally pulled the black-rifle market into the future. And the company isn’t done yet.

Olympic Arms is endeavoring into the realm of AR-10 rifles, but in typical fashion is offering much more than just a larger-caliber semi-automatic. In fact, the company’s new MPR 308/5.56 Rifle gives shooters a veritable cornucopia of calibers on one platform.

Olympic Arms has designed the rifle system to switch between its AR-10 upper receiver to any Mil-Spec AR-15 upper — regardless of caliber. Perhaps best of all, the system does not require any retrofitting to accomplish its conversion; out of the box it is ready to rock and roll in nearly any configuration a shooter can cook up.

The company has achieved this flexibility through some elegant engineering. This is particularly evident on the MPR 308/5.56's lower receiver.

The quick conversions are facilitated by two pivot pin locations milled on the lower. The longer local affixes Oly’s AR-10 upper, the shorter one pops on any Mil-Spec AR-15. The lower also has a slick mag well, milled to accept both AR-10 and -15 magazines. Of course, when it comes to the larger-caliber the magazines are proprietary; the smaller caliber, once again if it’s Mil-Spec it will work.

Finally, the company has redesigned the buffer system so it does not need to be switched for conversions. The bolt carrier in Olympic Arms’ AR-10 makes contact on the rim of the buffer, while the AR-15 makes contact on the center of it.

The convertibility of the MPR 308/5.56 gives it access to all of the standard AR-15 chamberings — 5.56 NATO, .300 Blackout, 6.5 Grendel, etc. But shooters will get to enjoy more than just .308 Winchester when shooting the rifle in an AR-10 configuration. Olympic Arms has a slew of calibers slated for the rifle in the future, including .243 Winchester, .260 Remington, 7mm-08, .300 WSM and .270 WSM.

The MPR 308/5.56 comes configured as a .308 AR-10 and is available with 16-, 18- and 24-inch stainless steal bull barrels. The MSRP for the rifle runs from $1,267 to $1,688 depending on barrel length.