If you really want to see your .300 BLK shine, quit changing your AR’s furniture and change your platform instead—to a bolt-action rifle.
Most folks might say the genius of the .300 BLK is its adaptability to the M4/AR-15 platform, and from a practical standpoint this is certainly true. The full-bodied projectile of a .30-caliber bullet certainly tips the scales of physics in favor of the .300 BLK over the svelte and speedy .22-caliber pill in the 5.56 NATO for AR-equipped mission. Not only does it deliver a far more caffeinated punch on its targets, but also it does so with just enough restraint to not over penetrate in a close quarters combative situation like the .308 Win.
First created as ballistic nourishment for AR/M4 operators who wanted more persuasion than the 5.56 NATO/.223 Rem. could deliver, the .300 BLK—an unofficial answer to the Russian 7.62x39 mm cartridge—enabled M4/AR users an easy upgrade in downrange lead.
The .300 BLK is no one-platform-only ballistic wonder. In fact, even in the seemingly pedestrian bolt-gun configuration, the squatty, pistol-powder-packed cartridge delivers on all of its better-than-a-5.56 mm campaign promises like being quieter than a 5.56 mm suppressed, delivering more oomph, and by virtue of its vastly bigger mass, doing more damage. The .300 BLK is a superb police sniper cartridge choice because it can be every bit as accurate as a sniper needs while not overpenetrating, and you can carry the same caliber of ammunition for your primary and secondary rifles, albeit snipers may want a different flavor bullet.
More and more firearm manufacturers are chambering factory bolt-action rifles in the .300 BLK. I had the opportunity to shoot a custom-built .300 BLK rifle manufactured by Sisk Rifles in Dayton, TX. The short-action Remington 700-based rifle used an 18-inch No. 2 contour Lilja barrel wrapped in Sisk’s unique Sisk Tactical Adjustable Rifle (STAR) stock. Similar to its AR/M4 brothers, the Sisk rifle had plenty of Picatinny rail space for any gadget an AR/M4 operator wants while adding a few tactically-superior advantages over your garden variety bolt action rifle like a fully-adjustable, all-aluminum stock and fully-rotating hand guard to give operators every bit of mechanical flexibility possible.
One of the advantages to the Sisk rifle is portability, not something normally attributed to bolt-action rifles.
Charlie Sisk and I ran through more than 20 different .300 BLK load variations which included several factory and hand loaded sonic and subsonic ammunition. Our 100-yard accuracy tests varied wildly from the best, Gorilla’s factory-loaded 125-grain Sierra Matchking which shot neck and neck with our hand loads of the Barnes 110-grain Triple Shock using H4227 powder at just about one-quarter inch to the worst, a hand loaded Berger 210-grain LRBT Target using H4227 which grouped nearly three inches. To be fair to Berger, slowing down their 210-grain LRBT from 1,405 FPS to a subsonic 1,007 FPS gave us a much better group of nearly 3/8-inch.
Clearly, the bolt gun platform doesn’t inhibit the .300 BLK, so the question becomes why use a bolt gun over an AR platform in the first place? The bolt gun has several inherent advantages over the semi-automatic platform that when combined with the .300 BLK give users plenty of reason to make sure their battery of firearms includes a rifle inspired more by Mauser than Stoner even when chambered in the .300 BLK.
First and foremost, the bolt-action rifle is by far much more reliable under any condition than the gas or piston-powered AR platform. There are simply fewer moving parts and the only gas your bolt-gun needs to operate is the oxygen its operator breathes to work the bolt. That bolt is going to cycle so long as the operator can and that leads us to the second, arguably most important advantage of the bolt gun and that is stealth. Operating a bolt gun is a much quieter process than the semi-automatic AR. Another advantage is a bolt gun isn’t going to blow through your ammo and your wallet nearly as quickly as an AR. Of course, the downside to the bolt-action platform is it simply can’t send as many rounds downrange as quickly, and there are absolutely many situations where the sloth-like speed of a bolt gun is a burden. But …
An advantage - and danger - of the .300 BLK cartridge is interchangeability with 5.56 NATO/.223 Rem. magazines.
At the end of the day I’m certainly not advocating you toss your .300 BLK AR in the trash. It’s a terrific hit-harder-than-a-5.56mm choice, but right next to it in your gunsafe ought to be another .300 BLK in a bolt gun for those missions when you need the .300 BLK to be just a bit faster, quieter, more accurate and absolutely, positively work.