Frank Green at Bartlein barrels uses the example of High Power rifle competitors using stock Colt 1:7″ rifles back in the day experiencing 4 MOA results with 55 grain loads, and sub MOA with the same rifle and shooter using the 69 SMK. With a bullet that isn’t over stabilized, factors that can be detrimental to accuracy, such as a concentricity issue, can be mitigated. Most barrel makers and benchrest shooters will tell you the best accuracy for a given bullet is obtained with a twist rate that just stabilizes the bullet. In many ways, the 300 BLK in design terms is the opposite of a modern match cartridge like the 6mm BR or 6.5×47 Lapua. This means smaller powder charges and faster powders. The 300 BLK has such a small case you are effectively loading pistol powder into a rifle cartridge. So why do I think the 300 BLK isn’t an inherently accurate? Two reasons, case capacity and barrel twist. SAAMI specifies a 1 in 8″ twist in order to stabilize the heavy loads, most of the uber accurate 300 BLKs you’ll see have a much slower twist to work with the supersonic loads. It may only be me, but when I do encounter a 300 BLK that shoots, it’s often not a true 300 BLK. Often they’ll ask something like, “I’ve been shooting and reloading for years, no matter what I try, I can’t get the gun to shoot better than 2 MOA, with an occasional 1 MOA group, why is this”? I’ve gotten quite a few emails from shooters with experiences mirroring mine. Was I alone in my 300 BLK experience? Apparently not. After a number or trips to the range and a lot of brass and bullets, I found a load that would work- note the bughole in the middle left side of the target below. Imagine dumping a pile of money into a rifle and having it shoot some loads nearly 4 MOA!- I was that guy- something I seldon experience during the load development process. It wasn’t the precision love fest I envisioned. It took 26 different loads to get it end up with both a super and subsonic load around a MOA. The rifle, as pictured above, includes the following parts from Brownells: I even took the time to order a special 1:7″ twist barrel from Bartlein barrel to give me the edge with the heavy loads. I spent a lot of time (and money) building this rifle. Years later, I headed out the range with a custom Remington Model 7 chambered in 300 BLK. The upper functioned flawlessly and accuracy was about 2 MOA, which it turns out, isn’t too shabby for a BLK, but was still less than I had envisioned, especially considering the 7.62x50WT and 30 AR rifles I was testing around the same time shot about 1 MOA ( read my 30 AR review here). Back in 2012, I reviewed the 300 BLK in a 16″ AAC upper with Remington super sonic and subsonic loads, a link to the post can be found here. On some well-known and established forums, you’ll note the majority of load development occurs at short ranges with 50 yards being common and 25 yard groups appearing at times! Take a look at some legitimate load development and testing and you’ll start to notice that it is very hard to get a 300 BLK to shoot consistently well with both a subsonic and supersonic cartridges from the same gun- a fact that has led a few major manufacturers to avoid introducing bolt-action rifles in this caliber. In my opinion, the bread and butter of the 300 BLK is short barrel rifle applications, especially with a suppressor (what isn’t cool about a 10″ 300 BLK with a can and IR laser?) Once you start trying to do other things with the 300 BLK, better options emerge. Note the relatively short (.145″) neck on the 6.5 PCC. AR-15/M16 cartridge line up (left to right): 223 Remington/5.56mm NATO, 6.5 PCC virgin brass, 6.5 PCC fire formed brass, 6.5 Grendel, 6.8 SPC, 300 AAC BLK, 7.62×40 WT and 30AR. This is certainly the prominent selling point of the cartridge, but one of the areas the 300 BLK will sometimes lack is accuracy. Beyond the upgrade in bullet diameter, the 300 BLK offers the versatility of heavy 220 grain plus subsonic projectiles as well as lighter supersonic offerings. The ability to shoot 30 caliber bullets from a standard AR-15 M16/M4 style rifle by simply changing the barrel and ammunition has made the 300 AAC Blackout (300 BLK) a popular choice for AR shooters looking for an alternative to 223 Remington/5.56 NATO.
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