The M4 platform has its detractors, but as long as it's kept relatively clean and well lubricated, it is as reliable as any firearm extant, and as for accuracy and ergonomics, the M4 is hard to beat. If the platform has any real weakness, it is the 5.56mm cartridge. Several cartridges have come down the pike recently that were intended to replace the 5.56, but the .300 AAC Blackout is, in my opinion, the most viable option.
The .300 AAC Blackout was designed to give the M4 platform increased power and penetration on intermediate barriers with minimal recoil while retaining the 30-round magazine capacity. Its designers also intended for it to provide excellent terminal performance and accuracy when run suppressed with subsonic or standard ammunition. After working with various Blackout guns for the last year, I have to say AAC met those design goals.
I currently own two Blackout rifles, a 16-inch gun from Ambush Firearms, which is the hunting division of Daniel Defense, and a tricked-out 16-inch carbine from Houston Armory. Both have collapsible stocks and are threaded for suppressors. Both have 1:8-inch twist rates and Geissele triggers.
The .300 Blackout, like the very similar .300 Whisper, is sensitive to twist rate. A 1:10-inch twist will easily stabilize standard 110- to 130-grain bullets, but the long, heavy-for-caliber 220-grain projectiles require a faster barrel twist. The problem is compounded when you download those heavy bullets to subsonic velocities. The 1:8 twist on my guns is a pretty good solution, but it is right on the edge; heavy bullets don't shoot quite as well as lighter bullets in my guns, and they shoot downright terribly in others. Were I setting up a gun exclusively for subsonic, suppressed use, I would choose an even faster twist rate.
I do a substantial amount of suburban hog control, and the Blackout has become my go-to round for that mission. Remington was the only company to offer Blackout ammo when AAC first introduced the cartridge, and
Remington's standard 125-grain OTM load averages around 2,350 fps from both of my rifles. That's pretty good considering the cartridge's moderate case capacity, but it's too slow to guarantee expansion with the tough, controlled-expansion bullets I prefer for hunting, and I haven't been impressed with the performance of the OTM or AccuTip on big pigs. They work just fine on smaller hogs, but I wanted a tougher bullet, so I started developing my own Blackout loads.
At the time, there wasn't much data on the Blackout, so I used .300 Whisper data, and I got a few pet loads from my friend and fellow IMO contributor Steve Gash. After tinkering with a dozen or so loads for the better part of a year, I found that the Blackout is, indeed, an accurate cartridge. It is also easy to reload.
I tried unsuccessfully to develop a really accurate subsonic load, and I had trouble besting Remington's load, so I gave up on that project for now. I did manage to come up with some very accurate handloads with heavier hunting bullets. My two most accurate loads are the 180-grain Speer Hot-Cor bullet over 15 grains of Lil Gun at 1,695 fps and the 150-grain Hornady SST over 15.5 grains of H110 at 1,822 fps. Both loads averaged around 0.5 inch from my Houston Armory gun, while my Ambush Firearms rifle averaged 0.46 inch with the 150-grain SST and 0.74 inch with the 180-grain Speer. I shot three hogs with the Hot-Cor load and two with the SST (all weighed between 80 and 140 pounds). All the shots were broadside, every bullet caused tremendous internal damage and exited, but all five pigs ran between 30 and 120 yards after they were shot.
I experienced similar results with Remington's 125-grain and 220-grain factory loads. Yes, the pigs died, but they didn't go down quickly enough for me. Consequently, I started searching for loads that might provide more immediate effects.
About the time I started searching for better loads, several companies introduced .300 Blackout or .300 Whisper loads (most Whisper loads should work in Blackout guns), including Barnes, Black Hills, CorBon, Hornady, and Summit. The new Barnes load really won me over. It's loaded with the 110-grain TAC-TX; a flat-base, solid-copper bullet with polymer tip that is designed to expand at Blackout velocities but stay together to drive deep. It averages pretty close to its claimed 2,350 fps in both of my guns, and it shoots headshot tight at 100 yards.
I've shot six hogs with the TAC-TX load so far. Those hogs weighed from 110 to 200 pounds, and they ran an average of 25 yards after they were shot. All were broadside shots through both shoulders. Two hogs dropped in their tracks, while the toughest covered just 55 yards in a wild, heart-shot dash. I was not able to recover a bullet, so my friend Irvin Barnhart placed a 200-pound boar on top of a 55-gallon barrel of water and shot the pig once through the shoulders and once on an angle that hit mid-rib and exited the off shoulder. Both bullets passed through and were recovered in the 55-gallon barrel. Both were pretty as a picture and retained 97 percent of their original weight.
Because of its accuracy and on-game performance, the Barnes load is now my go-to nighttime hog load. Sure, subsonic loads are quieter, but the TAC-TX load lets me hold dead-on a shoulder from point-blank to 200 yards, and I can easily make head shots with it inside 100 yards. With my Thunderbeast suppressor attached, it is quiet enough for late-night, suburban hunting. Subsonic ammo is definitely quieter, but I have yet to get the accuracy I require from such loads, and they drop so quickly that they really work best in a controlled environment, such as hunting baited pigs from a blind so that you can zero for the exact shot distance.
I will never kick in doors or snipe enemy insurgents with my Blackout, but the accuracy and suppressor-friendly traits designed into the cartridge for the military make the .300 AAC Blackout ideal for hunting, too. I'm not about to give up my 5.56mm ARs, but my Blackout guns are definitely good alternatives and have earned permanent places in my arsenal.