On the .300 BLACKOUT……perhaps the perfect battle rifle

            I missed the punch and reach of my 7.62 M-14 from the very first day that I had to trade it in for an M-16. I received an early M-16 in Vietnam and it was plagued with all of the horror stories you have heard. My main complaint was after running about 100 rounds through it; carbon blew back, fell into the lower receiver and locked up the selector switch on “SAFE”. It had to be disassembled and cleaned to correct the problem. I was not happy with it. I very shortly traded it for a 1911 and a 54 ton mono-pod for a sky mounted M-60.

            Despite my bad experience with the M-16, I later learned a bit more about the Armalite/Colt AR15 system and its inventor Eugene Stoner that led me to buy a 5 digit # Colt SP1 carbine with collapsible stock for $400 (Yeah don’t you wish!) I tricked it out a little and shot many rifle assault courses with it. It always performed very well, but still I missed the knock down power and reach of that .308 cal. Round.

            Many people tried to marry the AR system to the AK system to get the best of both worlds. I looked at many of them.  None were very successful. There was always a problem: custom bolts, magazines, barrels/chambers, ammo etc. were required. The options were the Galil by the IMI/ IDF but that was still .223, or find a limited production AR10 (licensed to Portugal and used in the Congo) and spend a fortune for what was essentially a big ugly gun with bulbous muzzle and large heavy magazines.

            I gave up the search many years ago….until the .300 BLACKOUT appeared. The whole concept of this rifle was one of those “It’s so obvious! Why didn’t I think of this?”

300 AAC Blackout1

            The .300 BLACKOUT round is a cut down (at the shoulder) .223 brass case, re-necked and sized for a .308 projectile from 110 to 245 grains. The nature of the cut down and OAL allows the use of ANY AR15 platform magazine with no alterations and full capacity. I won’t go into its performance (Google it) suffice it to say that it works great with light supersonic bullets ([email protected] in.) as well as heavy weight sub-sonic bullets (1287fps. @0.35 in.) that fire almost as silently as an H&K MP5SD while using a can. The BLACKOUT will also fire .300 Whisper ammo. .223 brass is readily available for reloading.

All AR accessories also fit the BLACKOUT rifles; as other than the barrel and chamber there is no difference in the two platforms. When Remington started to produce factory ammunition for the BLACKOUT its popularity and availability widely expanded. .300 BLACKOUT ammunition is now available (or will be soon) from at least eight manufacturers

You can now purchase: barrels; to up gun your current AR, complete rifles or uppers in many configurations from at least 10 manufacturers. Guns & Ammo devoted an entire issue to this rifle. It is a viable, working, and available .308 caliber AR system that minimally requires only re-barreling: magazines, bolt and bolt carrier all remain the same.

CMMG .300 Blackout upper on SP1 lower w/flip up iron sites and HOLO site on left.
CMMG .22LR Cal.BCG conversion in center.
Colt SP1 5.56mm upper w/Barska 3-9×50 IR scope

I’m pretty much old school, and like old retro guns, but just the same Magpul co. has its attraction to me and I was excited by this new upper. I shopped a new Magpul OD green forearm, collapsible butt stock and some flip up iron sites. I also ordered a Miculek compensator that is almost an exact match of my Umberger comp on my .223 upper, and dug out a new crush washer. I have a whole collection of optics to drop on from a simple reflex dot site, ranging 3-9×50 IR scope, to a Gen 3 NVD. Which upper will get what configuration remains to be seen. I still have an original Colt 4X scope for the carry handle .223 upper.

There are two problems with this conversion. The first is peculiar only to my very old SP1: The upper and lower both use a 5/16” pivot pin. Modern uppers (after about 1975) use a ¼” pin front and rear. This required a 48 hour search to find an eccentric pin that I remembered that Choate Machine and Tool offered many years ago. I found one from DPMS for about $3. Problem solved the upper and lower would now happily mate..

The second problem is much more severe. This is a SAFETY ISSUE! The nature of the .300 BLACKOUT using a cut down .223 cartridge means that you can inadvertently chamber a .300 BLACKOUT round in a .223 rifle or upper. The bullet will push back into the cartridge upon chambering and on firing it will feed you parts of the receiver and BCG. Not a good thing. As the same magazines can be used with either system, It would probably be a very good idea to dedicate certain magazines just to your .300 BLACKOUT and paint them or better yet alter their surface so that you can feel the difference. Perhaps an inner tube band around the base or different floor plates.

I have yet to fire this newly configured monster, I have plenty of .308 bullets, small primers, and can cut down my cases but the powder I needed is still unavailable due to the panic. Big surprise, I found a can of IMR 4227 stashed away. Looks like I will set up the Lyman press and put together a few rounds for a test.

If you have been planning on adding a .308 to your battery but were dissuaded by the cost, you might consider a .300 BLACKOUT upper at half the cost.

Regards, D.

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8 thoughts on “On the .300 BLACKOUT……perhaps the perfect battle rifle”

  1. I have both the AR 15 and the AR 10 in addition to a beautiful Springfield M1A or M14. Personally, the AR 15 is a plinker. I don’t consider it a main battle weapon, although it was the weapon I was armed with in Vietnam. Didn’t like it then, don’t like it now. Sure, the .308 rounds for the AR 10 and M14 (they’re the same) are heavier and more expensive, but I’m not humping the weight, so what difference does it make. The AR 10 is very accurate, but in my mind, the M14 outshoots both the AR 10 as well as the AR 15. With iron sites on the M14, I can out shoot the AR 15 which is equipped with a scope on a 100 and 200 yard range. Don’t know why, but the M14 is one heck of a weapon.

  2. I have been shooting my HK-91 for 25 years. I have shot most of the guns you mention, AR’s, M14’s & on & on. I still keep coming back to the HK 91. Find one gun, stick with it, keep shooting it, learn it’s in’s & outs, take care of it & it will take care of you.

  3. Capt. Mike,
    The M14 and the M1 are two rifles that to me you caress them when you pick them up. I love both of them. The AR 10 is nice, but it is the across the tracks cousin to the M14 and M1.

  4. Since writing this, My BLK has gone through a few changes, most of them to make it more tactically useful. To begin with it received a dedicated Lower with 2 stage trigger and Magpul colapsable stock.
    The Holo site was replaced by a Vortex Spitfire 3X etched prism site, upgraded flip up sites, an under barrel pressure activated IR laser used with NVDs. It also got the tactical package all rifles in our group have received and been trained with: Miculek compensator, Magpul B.A.D., Strike Ind. 30 degree ambi safety, Extended cocking latch and Magpul single point ambi sling attachment point. Hooked into this is our home brew bungee sling with HK clips. This package has been run hard on tactical carbine courses and performs!!! Shines close in and well out to 200 M in every possible shooting contortion. I have fed it a lot of Gorrilla as well as home loaded rounds with Sierras excellent 125 Gn projectile. These are contained in a MCM mag box. Those 15 magazines all have Magpul ranger plates designating them as ONLY BLK magazines, not to be loaded differently or used elsewhere.

    The SP1 has been returned to its original retro configuration that served me well through my years competing in 3 gun. I have also built a 5.56 super-carbine that has the tactical tricks as well as a HOLO site and flip to side 3X magnifier and IR laser. I use a CMMG .22LR conversion in to cheaply train with.

    My 24″ LR308 is in its final configuration: Vortex Viper 6-24X50 XLR FFP scope and mount with level, Atlas bi-pod, extended charging latch and Magpul PRS stock. An old M60 sling helps hump this heavy SOB. It is performing well on its way to 1000M shots, consistently ringing a 12″ gong at 500M. Needless to say I have not been posting much, but building and shooting. ,Regards, D.

  5. What does the 300 AAc do that the 7.62×39 doesn’t? Simple answer, not much! If you want to talk about suppressed use, load 150 grainers in the 7.2×39! If you are talking about cartridge and platform combined, it is hard to beat the 6.5 Grendel in the AR-15 platform. from up close to out to 1000 meters, it is useful and accurate.


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