One of the main attractions of AR-style rifles is how quickly and easily they are modified. A tweak here and there and the platform can quickly go from something akin to a sporter for hunting to a carbine ready to tackle the battlefield.

Recently, Colt has moved this concept to the next level with its M.A.R.C. 901 Series. The rifle comes outfitted as a 7.62x51mm NATO/.308 Winchester, but can jump to the smaller 5.56x45mm NATO/.223 Remington. The only requirements to make the switch are a Mil-Spec Colt upper receiver and fairly simple conversion kit.

But exactly how simple is it to switch calibers on the AR-10/AR-15?

Well, the above video from LeagallyArmedAmerica.com gives a pretty good idea, by switching calibers on the rifle the M.A.R.C. Series was based off – the Colt LE901. Really, going from 7.62 to a 5.56 is as simple as pushing out retention pins, swapping some buffer components, adding or removing a magazine adapter and throwing on the upper assembly . The procedure remains essentially the same for Colt’s new 901s.

What is especially impressive about the Colt system, as demonstrated in the video, is the speed it takes to switch calibers. They clock the process on the video and come up with 1 minute and 15 seconds.

It’s difficult to say if Colt’s concept has any potential to be a wave of the future, but it certainly does appear to be a convenient way to have two calibers on one platform.


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Leatherwood AR-15 Scope Value Pack