300 AAC Blackout Subsonic Velocity Data
As mentioned previously, I am working with a series of 300 AAC Blackout uppers courtesy of Deliberate Dynamics and Rainier Arms. These uppers have Noveske stainless steel barrels and will be run through a series of tests to determine their suitability for various purposes, both “military” and “civilian.” Jim of Deliberate Dynamics did the shooting today, while I “shot” photos. I particularly like this shot, which shows what I believe to be a bit of flame coming out the ejection port along with the case.
One of the first things we wanted to do was see what the performance of the 220 grain subsonic load was from these uppers. Since we had 8″, 10.5″, 12.5″ and 14.5″ barrels at our disposal, a good chronograph, and factory ammunition, it was a fairly easy task. These are preliminary numbers, and will be followed up with more thorough data analysis – but for now, they’re pretty solid.
I’ve been loading 300BLK for a few months now, but I think most people will be interested in the performance of factory ammunition. In this case, it was Remington R300AAC8 – the aforementioned 220 grain subsonic stuff. Although supersonic loads – and factory brass – have been promised for a very long time now, it’s disappointing to see that they have not been forthcoming.
We encountered no functional issues, which was a good sign for both the caliber and myself, since I put the uppers together. The Troy mags, as well as PMags, fed the fat 220gr loads just fine. If you’re not familiar with 300 Blackout, it uses 5.56 bolts and magazines, and a modified 5.56 case that’s shortened 10mm and necked up to .30 caliber. The advantages of 5.56 mags and the strength of a 5.56 bolt, as well as .308 diameter projectiles, make this a much better choice than 7.62×39 for the AR-15 platform.
As for the performance of the subsonic load, all shots remained subsonic, which is, of course, a good thing. However, this means that the guys with 8″ uppers are going to be using a load that’s a little slower than it could be, just so the guys with 14.5″ and 16″ uppers don’t have that supersonic “crack.”
The 8″ averaged 954fps, the 10.5″ 993fps, the 12.5″ 1014fps, and the 14.5″ 1025. This is clearly a load that’s optimised for shorter barrels. However, I wasn’t impressed with the standard deviation – over 40 in all but one example. And the extreme spread was, well, extreme, exceeding 100fps in several cases.
I would like to see more ammunition available in this caliber. Not only would more loads be nice, but I’ve never found Remington ammunition to be “the best,” or even above average. Right now, though, this 220gr load is just about the only thing I can find, other than expensive Cor-Bon stuff, and 175gr CMMG ammunition that reportedly won’t cycle in anything but CMMG uppers. I’ll be loading various projectiles, but as I said above, hard data will be presented with factory ammunition. My final report will be a comprehensive evaluation of the caliber.