Making the standard AR-15 into something more than an intermediate carbine is an old concept, going back to nearly the genesis of the weapon itself. It really hit its stride in the early 2000s with the Special Purpose Rifle (SPR) concept- a Small Unit level Designated Marksman’s rifle. It’s advantages are numerous; light weight, accurate and fast. While the original Mk 12 is a bit dated now, the concept of having a rifle that shares magazines and ammo with the other weapons on the team remains tactically sound and one that is particularly appealing to potential guerrilla forces, working with limited manpower and supplies. Among those of us that actually understand small unit warfare, the role of the sniper- remaining in the shadows and timing his attack when and where its most favorable to him- is the largest force multiplier. His weapon is just as important. The AR, when done right, can serve this role well.

The earliest SPR? M16 in Vietnam with Garand scope.

A Designated Marksman’s AR is a neat idea. It makes a lot of sense- even in its early days it was noted for its accuracy off the rack and in recent times, amid modern machining techniques and free-float tubes, its not unusual to see at least MOA-accuracy in even lower-end models. A one inch group at a hundred yards is pretty impressive considering that was considered match grade accuracy just not that long ago.

But the AR makes a lot of sense for other reasons. By the numbers, it is the most common rifle in the United States. In fact I’d venture to call it the world’s first truly open source weapon with the advent of small CNC machines, the proliferation of 3D printers and the sheer volume of manufacturers for every part a shooter would need in between. And while the quality might vary widely, quantity has a quality all its own. Second, because of the numbers, a team is much more likely to make it a standard weapon than say, an FAL, Mini 14 or AK. So the logistics of having ammo, magazine and parts interchangeability makes more sense. You can stock up on more parts and supporting gear that becomes standard across everyone’s weapon. Finally, today’s AR-15 is, at least in my opinion, the simplest weapon ever made to mount optics on. A quality scope, a set of decent rings or single piece mount, and you’re ready to rock and roll.

How Much Range Do You Need, Anyway?

How far is a realistic engagement range? There’s many other factors involved for a guerrilla marksman than simply hitting targets at extended ranges. Fieldcraft and knowing one’s enemy is more important.

A common complaint against the most common AR caliber, the 5.56, deals with carried energy at extended ranges. But at what ranges are you planning on engaging? Sure, it doesn’t carry the same energy as 7.62×51, but with the right ammunition load and understanding certain limitations its plenty combat effective. Within 300-500 meters, which is a near ideal combat sniping range in southeastern woodland, foothills and Appalachian mountains, the heavier loadings, such as 77gr OTM  5.56 perform pretty well.

Why 300-500 meters? For the guerrilla, one of the most important considerations that needs to be made on patrol is concerning indirect fire. In case you didn’t know, standing there and shooting it out with conventional or even special operations forces is suicidal. It doesn’t matter how many times you’ve rehearsed your immediate action drills, you have to always assume that the team you attacked has artillery and close air support. If its a Light Infantry unit, they’ll have mortars at the Company and Battalion level. 600 meters and closer is what’s known as Danger Close range. They’ll still rain steel on target, but it’ll take a bit longer to double check the calculations. But 300-500 meters is a happy medium for another reason. Panicked troops will have a much harder time spotting your team’s firing positions, and the hit probability from their weapons at 500 is much less than yours. The conventional Army’s basic rifle qualification is 300m, and often the 300m popup target gets ignored. And that’s out in the open. A guerrilla effectively employing the principles of camouflage and concealment is a serious menace.

The Rifle System

A Mk 12 Mod 1 in action.

The original Mk 12 SPR came with a stainless steel Douglass barrel with a 1/8 twist. The earlier weapon, known as the SEAL Recon Rifle, and the later Mk 12 Mod H, both had a 16 inch barrel for better portability. By the numbers, the most common ARs come in 5.56 equipped with 16 inch barrels. Even relatively low end barrels these days come in 1/8 and 1/7 twists, both lending solid performance to those heavier 5.56 loads. So while that 16 inch barrel may not be ideal for competitions, it definitely works well enough without being cumbersome in the field. Moving through wooded environments it’ll carry just fine. But if you’re into home building or are looking to upgrade your existing weapon, don’t skimp on a quality barrel. There is nothing that will make up for a poor quality barrel. And on that note, an AR being used as an SPR absolutely should be free floated. There’s no logical reason not to be, and it wrings every bit of accuracy potential out of your platform.

Another focus should be on a decent trigger. While the GI-spec trigger AR trigger can get better as it wears in, if you’re building the rifle from the ground up there’s better options. I’m preferential to Geissele, but Chip McCormick makes a decent trigger from my own experience and there’s several others out there that are tailor made for accuracy. I really like a two stage trigger to know exactly where it will break for a repeatable squeeze each time. But that’s me. As long as it’s consistent and comfortable for the shooter…its not wrong.

A modern take on the SPR, my BCM Recce 16.

Last, the optic can really be the deal breaker. One of the biggest advantages to the guerrilla is his ability to observe; a good optic enables us to observe our area in better detail. But too much glass is a bad thing for a lot of reasons, especially on a multi-role combat weapon. Originally the optic on the SPR was a variety of different Leupold Mark 4 models, most commonly being the MR/T 2.5-8×36. Anything from 4-10x is fine, as there’s a lot of good options. Personally I don’t favor any rifle optic over 10x magnification in this role. At 10x you still have a wide enough field of view at 300m to not completely lose your targets. But the point that a lot of shooters overlook is the value of a solid mount. You can spend all you want on quality glass, but if you skimp on the mount, you’re in for trouble. And if you’re not into learning how to read mils or MOAs, Primary Arms makes a very nice 1-8 with the excellent ACSS reticle.

Combat Effective for the Partisan

The world of the AR has changed a lot since the 60s. It’s changed a lot since the early 2000s and that much for the better. Between higher standards in manufacturing, the ability to make many components on your own and the improvements in ammo, the AR-15 has quite a bit of potential beyond the range toy that a lot of people own. A lightweight sniping platform in the hands of a solidly trained team is a lethal threat for an occupying force. Employing sound fieldcraft and proper camouflaging techniques, they are and have always been the most dangerous men on the battlefield.