300 Blackout - At long last, a review!

I specifically waited a while to see how this cartridge would take in the current market, but it is finally time to take it out for a spin. Having been a long time sucker for the venerable .30-caliber variety of projectiles, this was right up my alley, but the final clincher was being able to form the brass from .223 or 5.56 brass (something I have absolutely no shortage of). I therefore set about rounding up reloading supplies and upper receiver parts.

First Impressions: When I first started reading about this round, I was immediately skeptical of its published ballistics, particularly the effective range and the velocity. How the hell could this little case hold enough powder to drive a 110 to 135 grain projectile beyond 2,000fps? I get that most of the loading data uses pistol powder to make up for this reduced capacity, but with such fast burning powder it raises the risk (and the severity of the consequences of) loading mistakes, while also reducing the safety threshold for OAL. Don't get me wrong, I know that so long as you stay within the safe range of the published data, you should be just fine; the simple fact is that the safe range for this particular cartridge is less than one grain when loading with H110.

Loading Bench: I have to say, this is one of the most fun cartridges that I have ever reloaded. Initially, trimming the .223 cases down to length was a royal pain in the ass, but eventually i got smart (or lazy, depending on your perspective) and snapped up a harbor freight benchtop 2" chop saw. First I removed the cheap-o vise that came with it and replace it with a home made jig to chop every case to the same size (in this case, I was chopping them just below the neck, to about 1.40" to allow room for error). To make things easier on my sizing die, I did a quick deburr on all the cases before grabbing the sizing wax and sizing the whole lot. Now it was time for a quick spin on the case trimmer, a date with the chamfering and deburring tools and finally a good cleaning in walnut media.

One issue I did note was that the partitions in the .223 ammo boxes I was using to store the cases are actually higher than the sized 300 BLK cases, making it difficult to remove any single case. Anyway, loading was a breeze. I've never used H110 before, but it meters very well in my powder dispenser.

The Rifle: I wasn't about to plunk down the money for a commercial upper or a full up rifle, so I ended up building my own. This being a relatively light recoiling round, I ended up going the direction of an ultra-lite AR upper to slip onto the lower from another of my rifles. I manage to get my hands on an AR-Stoner lite contour barrel, a DPMS slick side upper (my personal preference, for simplicities sake and because it fits very tightly to a rock river lower) Yankee Hill Gas system parts and a Midwest Industries rail system.

At the Range: I started out testing a series of 110gr Vmax loads along with a number of 135gr SMK loads. I was initially expecting the SMKs to be the real tack drivers (based on previous experience with .308s and .223s) but was surprised that a few of the little red tips printed very respectable sub-moa groups (best group was .85"!), while the match kings hovered around the 1"-1.25" area. Not bad at all out of a little 16" carbine!

Now for the bad bits: My biggest issue was a huge number of double feeds and failure to extracts with the SMKs. At first I thought it was something wrong with the gas system (not quite lined up perfectly?) but after stripping it down and re-aligning it, the problem persisted. After some trouble shooting, the culprit revealed itself: The hydraulic buffer system I had installed was slowing the bolt carrier enough that it was not cycling fully. The first symptom was that the bolt didn't lock back on an empty magazine, with double feeds being the eventual result of my not correcting the problem. While this never occurred with the Vmaxs, I believe it is because there was a larger charge of powder behind the little hornady bastards that gave them just a little more gas pressure to cycle fully.

Another thing I noticed is that chopping and resizing the thicker lake city 5.56 brass was a bit more dicey than the bulk box federal I ended up using exclusively. The 5.56 brass that I did end up with was very tight in the chamber, making extraction very difficult; likely will not be resizing surplus brass too 300 BLK again.

Overall: Love it. This little bastard is a great addition to the gun safe, especially for someone who reloads. Being able to chop and resize shot out .223 brass makes makes it a very good value to anyone who handloads, while the standardized caliber (.308) makes it easy to find bullet options. The AR platform compatibility is perhaps its best feature overall, and makes the 300BLK a very sturdy chamberings that is likely to outlast many of the other fad cartridges that have come on out in recent years.