Collapse bottom bar

Guns & Ammo Network

Ammo Hunting Rifles

AR-15 Debate: Can the .300 Blackout Really Replace the 5.56?

by Greg Rodriguez   |  October 3rd, 2012 79

The .300 AAC Blackout puts added stopping power in the M4/AR-15 platform while maintaining a high magazine capacity. The author test-fired both handloads and factory-loaded ammo: (left to right) Barnes 110-grain TAC-TX, Hornady 150-grain SST, Remington 125-grain OTM, Speer 180-grain Hot-Cor, Remington 220-grain Subsonic.

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.


Click to enlarge.

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.

300-Blackout_003Because 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.

  • bobthegunslinger

    awesome write up!i`am just hoping ammo pricing will start to go down,as subsonic ammo is ridiculous and supersonic is on the fringe of affordable!

  • Gary

    The 300 AAC looks like a good cartridge for close in targets but the purpose of the 6.8 was to maintain the flat shooting trajectory of the 5.56 while delivering more ft lbs/penetration at longer ranges…I'm in Montana and you would be greatly hampered using a 300AAC out here…Its way to slow to be an all around round…Its a niche round…

    • bobthegunslinger

      dude,sorry but how many people even live in montana?this is a great covert military round and is well suited for hunting hogs and deer!isn`t that enough of an overall round to be mainstream and not niche as you suggested?sure the 6.8 spc2 is a great round for hunting and long range targets,but it doesn`t fit the bill that the 300 blk does!

    • Steve

      A 5.56 MIGHT tumble to produce a wound channel as big as a .30 cal, but with the military's faster 1:7 twist rates they typically just punch through. A .30 cal, even at moderately lower velocity, is a better people puncher. And with the M4's 14.5" barrel, that 62 grain 5.56 load was only going about 2800 fps, compared to 2400 fps for the 110 grain .300 BLK. Not a huge difference in velocity, and only a very slight difference in trajectory out to 300m. Add to that the growing popularity of the 77 grain 5.56 load, and the gap gets even closer.

      • Steve

        Ignore this post, it was meant as a reply to someone else further down.

    • chris

      How rue, in Nevada that cartridge would be all but useless except for home defense I would still prefer the 6.8. Dose everything the 300bo dose and alot more

  • don

    Why re-invent the wheel? The 7.62×39 has the same ballistics and is easy to reload and is widely available.


    • Richard

      Could not agree more, Don.

    • I carry

      Not to mentin the ammo is readilly available and CHEEEEEP.

      I couldn't agree more. Typical bureaucrat. reinvent the wheel….why?

    • bobthegunslinger

      our military won`t be handing out ak 47`s anytime soon,so the military has deemed a new cartridge necessary! plus it`s just a barrel change and a different bullet!

      • Christopher Scott Renfro

        Rock River came out with an AR that shoots the 7.62 and accepts AK mags…it's nearly perfect…except for the fact it's about $1000 and you can pick up an AK for $500 everyday.

        • Steve

          But the military doesn't want a completely different rifle. The .300 BLK allows the gov't to order some new barrels and leave everything else the same. No new bolts, no new mags, no new lower receivers designed to take special mags. Just a barrel. That is not reinventing the wheel. That is inventing the tire.

      • LeftyEye

        Just jumped into the .300 BLK game myself – and am a lefty-only shooter – so as soon as someone comes up with a lefty AK, I might take the plunge! (Just kidding!!!!)

        Ready for the flames, bring 'em on!: Those who suggest "just get a second gun – cheaper than converting your AR – and certainly cheaper than a whole new upper!" must not be as serious about shooting "consistency" as I am.

        I bought a tack-driving Stag Arms AR-15-1L, then quickly added a .22LR conversion kit so I could get serious practice time in for mere pennies before switching to 5.56 / .223 ammo. I was able to build up SO much more confidence, arm strength, breathing practice, etc. – by using hundreds of rounds of .22LR! Switching to .223 rounds, I was picking up the exact same rifle – weight, balance, trigger pull, cheek-rest position … priceless amount of everything saved by going this route. My first 20 round mag of .223s, I shot the 1" black center right out of the range target.

        Decided to convert an entirely new upper to .300 BLK for the exact same reasons! I'm still shooting the *exact* same rifle – BY FEEL! – and that's darned important to me!!!! Used a Stag Arms 1L upper – and went with the amazing Carl Caudle AR M4-profile polygon barrel from Black Hole Weaponry in WA. Think of a 16 inch Glock pistol chambered for .308 rounds! FIrst box – after bore sighting and using a cheapo 4X scope – absolutely dead-drilled 18 out of 20 sent down range from 100 yards bench-rested!!! My .300 Blackout shot … the black out!!

        Then, went oink-oink hunting in upstate SC and the party of 4 all brought home "the bacon". Three shooting ARs; me and the .300 Blackie. I was the only one who needed just *one* round to drop one like it had been pole-axed. It was a two-hitter: I hit IT; it hit the ground. None of the other three went down cleanly, one was a runner and two required a second shot – and not only was mine the largest piggie taken, it also wasn't the best-placed round – – – yet the .300 BLK did the job better – BY far!

        Nay-sayers, say what you want about a .300 Blackout conversion – or an entire new upper – on an AR-15. In *MY* case, I have the exact same "platform" – the touch, the feel, the weight, the balance, THE TRIGGER PULL! . . . from which to launch el-cheapo .22LRs, .223s, 5.56 NATO (even steel-tipped "penetrators") and assorted AK-style punch – down range with one lower and two uppers.

        And in the case of *MY* .308 rounds, with better accuracy out to 200-250 yards than any AK shooter could ever dream of! Basically 3-1/2 totally different rifles – the .22LR, a semi-auto M-16 (5.56 rounds), the .223 plinker – and the 7.62 X 35 AR – and they all "feel" the same when I pick the basic rifle up.

        Can't wait for deer season ….

    • HogsTooth

      Don…are you saying that the Russians had it right all along? GASP!! All this expenditure on the pursuit of the perfect cartridge seems ridiculous. In 1906, Remington developed the 30 Remington which is perfect in almost every way. If you want long range high velocity, it can be loaded with lightweight sabot bullets. For heavier hitting, 120-150 grain bullets are ideal. It easily can replace both cartridges and can all be done with one rifle, and this was done over a hundred years ago.

    • SanDiegoShooter

      The primary excuse is that the 7.62x39mm does not feed very reliably in an AR15 upper. That is the premise of the article. No one is suggesting replacing the AR15 with an AK47; even the russians have moved on to the AK74 in 5.56mm. There is also the limited supply of bullets in loaded ammo, although that could be easily fixed, if Nosler is loading Partitions in factory ammo, you arn't going to get 20 cent per round ammo.

      • NOYFB

        AK74 is 5.45…just a bit narrower than the 5.56

    • Benz

      yea, why bother… we all know that 7.62 x 39 is so accurate.

  • SanDiegoShooter

    Replace the 5.56mm? No way. Frankly, as a military round, you cannot use hollow points, but you can get a light, high-speed bullet to tumble on impact with a similar result. The 30 cal will penetrate obstacles better, but the AAC cannot compete with the .308 and it is doubtful soldier are going to carry a selection of uppers with them. As a hunting cartridge, you can't hunt in most place with anything smaller than a .243 (6mm), so that is off the table altogether. If there is going to be a compromise it will probably be in the 6.5-6.8 mm range with a beefed up rifle that can move a 100 grain bullet at 3500 fps. I've also never seen a head to head comparison of the 62 grain penetration round; it's alway about the 55 gr FMJ. Just makes me wonder if a clip change can be as effective as a rifle change.

    • Steve

      A 5.56 MIGHT tumble to produce a wound channel as big as a .30 cal, but with the military's faster 1:7 twist rates they typically just punch through. A .30 cal, even at moderately lower velocity, is a better people puncher. And with the M4's 14.5" barrel, that 62 grain 5.56 load was only going about 2800 fps, compared to 2400 fps for the 110 grain .300 BLK. Not a huge difference in velocity, and only a very slight difference in trajectory out to 300m. Add to that the growing popularity of the 77 grain 5.56 load, and the gap gets even closer.

      As for hunting, I'm not sure what your point is about the .243. Where hunting regulations restrict cartridges by caliber the .300 BLK will always be acceptable, even over the .243. It is a larger diameter round. Restrictions byft/lbs are very rare and I know of no American jurisdictions using them. The .300 BLK is legal for deer and hog anyehere that rifle cartridges may be used for big game hunting.

      • Eric

        For SDS, the original 5.56 was designed to tumble upon impact. The speed, rate of twist and weign of the bullet all conspired to create a projectile that was on the verge of ballistic stability. I have read many accounts of firefights in VietNam where the G.I.s would open fire at relatively short distances in dense cover and miss. Granted there are other factors at play, but the ballistic instability of the 55 grain projectile out of a 1 in 14" twist barrel don't help things.

        Steve, the great state of Nebraska DOES, in fact, restrict the use of loads on large game based upon the energy produced.
        Firearm- 22 caliber or larger with minimum of 900 ft lbs. energy at 100 yds. and 357 magnum rifles and 45 colt rifles, and shotguns 20 gauge or larger with single projectile and handguns with minimum of 400 ft lbs at 50 yds.

        • Steve

          Thanks Eric, I wasn't aware of Nebraska's regs. Learn something new every day I guess.

          You are spot on about the twist rate. The original was so designed because bullet tumbling was perceived as the next best thing. Problem was, a round on the verge of instability tends to tumble in flight if conditions aren't perfect. Rain, fog, and even cool weather would upset the original setup and cause it to destabilize in flight. Faster twist rates solved that problem, but also did away with the original point of the round, which was to tumble for wounding effect.

          Years later, we are using rifles with a 1:7 twist pushing 77 grain lead-free bullets to about 2650 fps and people still think they will behave the same as the original 52 grain load with a 1:14 twist at 3200 fps.

  • Bob

    I see the shooter here has a problem with bullet placement, I took a 180# boar with a 55 gr. FMJ in a 22 hornet with 1 shot at a 100 yards in the head, most the time I use a 6mm with a 100 Gr. bullet and I have never had one get up and run, they drop in their tracks. I have a 300 whisper in a TC. contender with a 14 inch barrel and have taken several pigs with it out to 200 hundred yds. I just bought a new DPMS AR-15 in 223 and I would not be afraid to take a hog with it out to 200 hundred yds. with the right hand load. I load for 17 centerfire up to 45-70 in TC contender's and have been reloading for close to 40 year's now Bob

    • Eric

      I would agree Bob, but handloading component companies don't advertise as much as the ammo companies. Look at Barnes, they get $35 for a box of 50 bullets or $40 for a box of 20 loaded rounds, where do you think the higher profit margin is? So which are you going to encourage the writer to push?

    • SanDiegoShooter

      Dear Bob, try putting on your reading glasses before throwing insults. I did not say the 5.56mm wasn't capable, I said it was ILLEGAL in many states to use anything smaller than a .243 on anything above varmints. Like many laws, it is out of date and based on false assumptions, kinda like your insult.

      • Bob

        First of all I was not talking to you, I was talking to Eric. If you live in San Diego Ca. you should know you can use any center fire rifle to hunt big game and any pistol larger than a 38 special. You need to know your capables as a shooter, I have killed Ca. deer with a 17 remington center fire before, so I was not putting you down. If you know of a 243 that will take a beating like a AR-15 in 5.56 please let me know. I shoot a 6mm for Ut. deer and would not afraid to take an elk with it. It is in the shot placement, I love to use the smallest cal. I can use on the game I am hunting, because if I can't place my shot where I want it to go I won't shoot and that is the way is. PS I have never lost game animal yet. Bob

  • David Ransom

    I wonder how it compares with the 30 AR that Remington developed for the R-15.

    • @Lakan_Kildap

      .30 RAR too fat to fit double column in an AR magazine, which limits its military potential. But personally, I think the .30 RAR would make a great SAW round. With a belt fed gun, doesn't really matter if the round would stack single-column or double-column, they're all single-column in a belt. The .30 RAR instead of 7.62×51 for the SAW would mean less wear on the gun.

      • Charles

        The SAW fires 5.56mm. The 240G fires 7.62×51

  • Charlie Rigoglioso

    While we are on the subject, sort of. How accurate is the Russian 7.62 x 39 in an AR platform? I have a mini 30 that shoots ok but only with cheap Chinese ammo. The 300 sounds great for close up work but not as a replacement for the .223 We still have lots of M-14's and 308's in inventory.

    • Bob

      Charlie, be carefull shooting that cheap metal cased ammo, DPMS states the coating they put on the cases heates up an transfers to the chamber and increases the chamber pressure and you could have a problem with the gun. Not from me it was stated in my instruction book when I bought the AR-15 from DPMS. about shooting cheap ammo. Just though I would pass it on. Bob

      • Name

        You're referring to the lacquer coated cases. After shooting several rounds the lacquer melts off and stays in the chamber. The problem arises when the chamber cools and the lacquer hardens. I believe this is the reason Wolf switched to a polymer coating of their ammo. In an AK, it doesn't matter because of looser tolerances, but in an AR, it matters. I'm curious if Hornady uses lacquer or polymer on their steel match ammo?

  • guest

    I recently purchased the AMBUSH V7 IN .300 AAC BLACKOUT and I couldn't be more pleased with the performance. It's great plinking with the 110 grain ($10.00 a box on line) and the 220 grain for around $24.00 a box. I love my AR's but this just feels right. When I shoot my SKS or my SLR-95, the thump of the 7.62x39mm is different and I would not compare my .300 blackout in anyway to a 7.62x39mm. I had the 7.62×39 upper for my AR but the accuracy was not there and the mag feeding problems was too much so I sold it.
    I too am hoping/praying that the ammo will continue to come down in price because I don't reload.

    • Kenny – Tampa

      Fantastic post !!!! I too purchased the Daniel Defense V7 ambush .300 blackout in realtree camo and I love it. The feel and recoil is almost the same in my eyes to the AR-15. I have been buying the remington 110 grain but the 220 grain will not cycle without a suppressor in my experience. (I have a AAC suppressor)
      I also own the SLR-95 (bulgarian) and it also shoots like a dream since day one. I now have 3 "go to" choices when the poop starts hitting the fan.

  • Bob

    Eric I here what you are saying, I bought in bulk years ago and am still shooting reloads from the 70's. Now it is just about as cheap to buy factory than reload. I am lucky to have done this, like I have 10,000 primers all different sizes, wads for shotguns primers for them, powder that cost me $4.95 per pound, 8 pound cans powder, and I had 1,000 once fired 223 cases for 20 years and did not know what I was going to do with them until I bought my AR, never owned a semi-auto before, I am useing up all my old bullets primers powder and the 223 cases, I have 250 223 cases left to put bullets in, I ran out of 55 Gr. FMJ's to play with. I have 30, 30 round clips for my AR. Some of the 22 cal bullets I have loaded did not shoot very good in my hornet or my 22-250 so I am useing them in the 223 for play . When I use all my stock I will bite the bullet and replace. 30 years + of being loaded is long enough, don't want it to quite on me when I might need it real bad. Bob

  • jeepers creepers

    I have to reload for 80% of my handguns. Rifle brass with a 10 or 12 inch barrel. I had many 5.56 handguns and did not like any of them. The blackout is just like the 300 whisper which is a great round for a handgun. It sould be great in a shorty barrel rifle. The only semi auto rifle I own there is no over the counter ammo for it so I have to reload it also (7,7×39). Or call it a 303 british barreled COWBOY CARBINE made in 1993 and only imported to the USA from June 1992 to SEP 1993. Looks like a SKS but is "NOT" by any means. Has a .3125 bore and SKS ammo is the wrong DIA. The bolt pushrod loads up with "RAW" straight from the case gunpowder if you use SKS or AK ammo. That I feel if set off would be the end of me. I fired one round and checked the bolt push rod "very GOOD THING".
    Yes the 5.56 is old and tired and needs replaced. I like the 300 blackout. very good round. Just keep it out of the hands of nuts.

  • Fred

    new 30 carbine!

    • @Lakan_Kildap

      Agreed, same bullet weight (110 grains), but more streamlined, and with a bit more sizzle.

  • Captain Bob

    On thing everyone is forgetting is the advantage to the soldier to carry much more ammo with the 5.56. You put big heavy bullets onto cartridges and the total weight to carry will cut down on how many spare rounds a G.I. can comfortably carry.

  • Starky

    I enjoy reading about all the new cartridges and some are very interesting, but to many are here today and gone tomorow. In the last couple decades the ditches are littered with these cartridges. In talking with those who sell firearms a lot are not carrying weapons in all the new calibers. They sit on the shelves too long as people are worried what if I buy it and it does not catch on. Ammo availabilty is often a problem. Not to mention the comapnies which manufacture the reloading components often wait to see if it will be a hit or not. Often these new calibers are just remakes of something that has all ready been. Just like the Remington Ultra Mags. Good calibers but the Wetherby's have been doing it for decades. I still like cartridges that if in a pinch I can by at the corner gas station and offer a unlimited amount of choices for reloading. (Capt. Bob a very good point.)

  • Eric

    CPT Bob, and I suspect that you are actually an officer, since you accurately parrot the DoD line for the past 50 years. The flaw in this argument is that it takes three to four times as many rounds to drop a target as clearly evidenced by the exeriences in Somalia, Iraq, Afghanistan, etc. Why do you think people, namely SOCOM troops and their many contacts within the arms and munitions industries started working on new cartridges like this? They wouldn't be trying to reinvent the wheel is the wheel didn't leave something to be desire.

  • @Lakan_Kildap

    .300 BLK/.300 Whisper/7.62×40 Wilson Tactical are basically the AK round but without the pronounced taper of the Soviet round. There are slight differences in performance (the 7.62x40WT is closer to the M1943 7.62x39Soviet), but only the coroner and cadaver would know.

    But if the .300BLK is to be adopted, it would mean a shift in US ballistic doctrine. Since the .30-03 became .30-06 in 1906, US main battle rifle cartridges have always been fast. Going down to 2,300-2,400fps brings the US back to the .30-03 velocity range.


    One thing everyone is forgetting is the 5.56 is not just the standard cartridge for the US, but it's the NATO standard as well. I don't think the US can just adopt a new round without NATO approval….kinda defeats the purpose of having a standard round.

    • @Lakan_Kildap

      The US adopted the 5.56 in the 1960's while NATO followed only in the early 1980's, standardizing on the Belgian version (SS109). Plus, let's face it, NATO follows the US lead, just look at all those Allied infantry rifles that must now be able to accept the M-16 magazine.

  • Long Shot

    In reference to many of your comments which are all in some way valid I think some of you need to leave the military discussion aside if you have none of your own experience and your relying on your SOCOM buddies who may be full of it. I say that because any real SOCOM guy fighting daily knows the benefit of his 5.56 compared to a 300BO and if you added up every poser who says they served in SOCOM the past decade I bet the math would be well over twice the real number and if you added up all the insurgents that those same posers say they have killed it would be three times the population of Afghanistan. I have served within SOCOM since 1997 in every country Eric mentions and many more. I own AR rifles in 308, 260, 300BO & 5.56. I would not carry a 300BO in combat because you cannot count on every battle being a close quarters one. My reason is simple and I will keep it currently relevant which is AFG and the average engagement distance in AFG is beyond 400 meters on a daily basis which is beyond the 300BO effective range. You need your 5.56 just to hit what your shooting at because your also shooting low percentage targets meaning real people do not stand in the open to let you kill them(well some do.) If I was a police or SWAT officer I would love the 300BO and carry it without any hesitation. Do I love 5.56mm? NO. Why? Terminal ballistics but if you can't hit the insurgent beyond 400 meters because your 300BO ballistics are not effective then terminal ballistics do not matter. So in combat comparison 5.56 versus 300BO? 5.56 for sure. I am starting another reply for hunting.

  • Long Shot

    As stated in my military reply I own AR rifles in 308, 260, 300BO & 5.56. Hunting is a closer argument than any military discussion about 300BO versus 5.56mm/223 and i think it comes down to one simple topic which is your geographic location or more importantly the typical distance you hunt meaning if you hunt the eastern United States your probably not considering shots 300 meters or beyond. On the contrary Gary from Montana or his western hunting brothers certainly shoot much further than 300 meters. I support Gary's reply that he does not prefer 300BO because I have hunted out west and they need better ballistics for the distances they typically hunt and the fact that their prey can see farther. I live on the east coast and love my 300BO for deer out here but just last week I took a bull elk in NM with my .308 Larue OBR and I would never consider a 300BO for a western hunt even for western deer due to the range limitations of 300BO. For deer out west I would carry a 5.56mm if I had to pick between the two cartridges but the best AR cartridge for the west is the 260 Remington but that is another discussion. One additional consideration for 300BO is reduced recoil for children. I like the caliber for my daughter when she hunts deer. So you can argue either caliber but based on where you live I will bet your choice is pretty obvious.

  • chemcmndr

    I've managed to get a very good subsonic hand load with the 220 gr SMK bullet using 10.6 gr of AA 1680, Reming 7 1/2 primers and 2.090" OAL. From my 9" AR upper, I was getting 1" groups at 50 yards and the average velocity was 1037 fps.

  • Jim McCain

    The answer is simple NO. The .300 Blackout is too small and slow to be effective past 150 or so yards and would be a step backwards. The ideal cartridge for the AR-15 platform would be much better suited to the 6.8 SPC or the even better 6.5 Grendel. The Grendel is ideal. It has excellent ballistic coefficient and is almost as good as the 7.62 Nato at distance.

    • Chris

      You are so right jim if actually knew what they were talking about this discussion would be much shorter.

      • go4it

        in the simple equation of physics, F = M X A – Force equals Mass times Acceleration – it shouldn’t take a whole lotta rocket science to see that a slightly heavier .308 round from a 300 BLK – although traveling a little slower – actually puts more *FORCE* – lbs/feet of ballistic energy – on a target downrange than the 5.56 NATO round.

        Bigger wound cavity, too. Not that getting zapped by either would be a joyous occasion but getting popped – in the same part of your body – with a .300 BLK vs. a 5.56 NATO truly WOULD BE a matter of life-and-death.

        In a CQB (close quarters battleground / assault rifle), the modern Middle Eastern engagement stage is well inside 250 meters. Any farther and it’s a case for a “specialist” (sniper), who then neutralizes the random threats. In house-to-house encounters, however, it’s pure one-shot or one-burst stopping power that matters and our troops shouldn’t have to be out-gunned by the 7.62 rounds from those old AK-47s.

        In the REAL world, I have before – and after – hunting experiences with wild boar in SC. I’m NOT the best shot – thought I had my sighting and ballistic info squared away – but first time out, did NOT manage to drop an oinker with one shot using 5.56 rounds.

        Next season, only 3 engaged but went *down* with the 300 BLK. 2 were single shots; the other was simply a p!zz-poor first shot that spun him around but the second was an absolute no-doubter. The other two one-timers were high cavity, 6-8 inches behind and below the shoulder … and the results were pretty amazing. Just “boom!” and …. DOWN! 80-125m using 147gr OTM slugs, hand-loaded with Hodgdon H110.

        • Justin

          In Afghanistan, some of our engagements were within the 250m range, but most were 500+m some engagements being initiated 1 kilometer away. Having to maneuver to within effect range of the 5.56 under fire can suck.

          • go4it

            I realize that – and am glad you’re safely back home. Thank you for serving our country!

            In any military theatre, the general military “rule of thumb” applies: When your enemy is within range, unfortunately, so are you … :(

          • Freedom?

            The U.S needs to adjust it’s combat strategies to the enviroment, not just adopt new paper clipped on methods to old meathods of engagement.

    • Kevin

      Two days ago i grouped consecutively two inches at 220yards with my Daniel Defense 300 blackout using 150grain and ACOG as my optic. This round delivers more striking force then a 5.56 would attain at that distance and the rifle itself is accurate up to 750+ meters in the right hands.

    • 1911a145acp

      Which 300BLK? SUB-sonic perhaps. 300BLK is certainly much larger ( diameter ) and most loads are heavier than 6.5 Grendel.The supersonic loading w/110 grain bullets is nearly the equal of the Grendel with MUCH easier logistics and compatibility in the M-4 platform. 6.5 Grendel has a very modest increase in downrange ballistics on paper- but requires special magazines, special bolt head, special springs, gives up slightly in magazine capacity and has VERY limited envelope in performance and very limited availability in bullets and factory ammunition loadings. 300BLK makes much more sense in nearly every category of comparison.


    When the M16 was first thought of, I believe Eugene Stoner was on the right path with using a smaller cartridge, but he just went a bit too small. I like the 5.56 round, but if he had used the 243 winchester, then you would have had an even better rifle.

    • Chris


  • Mack Missiletoe

    No. The .300 Blackout will not replace the .223. Two different tools, based on caliber and physics. And… the 7.62×39 still exists!

    According to history, we are supposed to upgrade to a smaller caliber… let's see… looks like we will be going from .223 to a .17 caliber! haha, joking on that one.

  • cody

    the armalite AR15 (stoners first design) as supposed to use the 7.62×51… in government testing they made him change to the 5.56 because that had become the standard NATO round soo really the "AR-10" is what the gun was supposed to be. I think the blackout is a great idea.

    • Husker

      Seriously? Are you in fifth grade? NONE of what you said makes any sense! You have to bring your A game around serious shooters in a place like this. Go do a little research and come back when you have a clue.

      • Freedom?

        The AR10 was made before the ar15. The AR15 was made for better functionality(combat operations, maneuver ops) than the technology would allow for an AR10 of the time.

        The ammo weight was also a HUGE consideration of the AR15 being made to replace the M14.

        Not to mention all the political maneuvering involved in not only the M14 over the FAL, but in the M16s implimentation over all others.

    • Chris

      Ah, no not true. The 5.56 was so we could carry more ammo

  • Gary

    The effects of the 55 gr fmj weren't designed to tumble…it's fragmentation effects were stumbled upon and then slowly as its lack of effectiveness in anything but very close quarters or a jungle were discovered that was the reason for the heavier bullets…By heavier I mean up to the current 62 or 77 gr bullet…It would be more lethal if the 62 gr bullet wasn't so hard with its penetrater tip…The 77 gr is actually a match bullet I believe with a cannelure…I don't know why they just don't settle on a good 75 gr bullet and get on with it?…Either way the 300AAC isn't as good of an all around cartridge…

  • Charles

    The 55 gr FMJ round used by the military does not tumble or fragment. The bullet yaws. This means when the bullet strikes, the front is slowed by impact while the rear continues on a super sonic. The bullet's rear cants back and forth sort of like a toy top on its last couple of rotations. This is what causes the devastating wound channels and it has more to do with velocity than any other factor.

    • Husker

      Thought we had been over this…but let's just say you need to read previous posts. The Russian 5.45 ball ammo WAS designed to yaw, the bullet has a hollow cavity (not point) that collapses and causes the bullet to yaw.

      • Charles

        Yes the 5.45 was also designed to yaw. Wonder where the Russians picked up on that idea.

  • @Average_Casey

    While the 300 Blackout looks like a great round, I don't think it's the best replacement for the 5.56. I think the best replacement would be the 6.5 Grendel. The round goes further than the 5.56 because of the ballistics coefficient. It carries a lot more energy too. The effective range on the round is great too as theres an article about someone taking an Elk at 400 yards with one last year (I think it was the owner of Wilson Combat but I may be wrong). I'm going to build an AR-15 in it this year).

  • Designated Marksman

    Actually the effective range of the 300 blk is 496 meters out of a m4. All the projectiles for the 300 blk have high ballistic coefficients. That means more retained velocity and energy at range. Combined with an acog calibrated for drop out to 800 meters it would be a big improvement in terminal ballistics over m855 ball at any range.
    If i can use a trijicon rco m4 and make e type target hits at 800 with m855 ball im sure it would be even easier with a 300 blk.

    • Chris

      Ya at 496yards you might as well be shooting at birds chart its drop at that distance I ate just did.

  • DetroitMan

    The 300 Blackout is not a good replacement for the 5.56mm NATO. One of the biggest shortcomings of the 5.56 is effective range, and the 300 Blackout has even less. IMO the 6.5 Grendel is the best available replacement, followed closely by the 6.8 SPC.

  • JackJones

    I went with a .300 Blackout barrel on a completely new upper half – NOT as a replacement for my standard 5.56 – but as an added option. I simply wanted more stopping power than the little 5.56 / .223 could ever hope to give me. The 7.62 bullet – despite being slower then the 5.56 – is also far more stabile in flight … and out to 150m or so, that's directly related to accuracy. I've – consistently!!!!!!! – bulls-eyed the same target at 100m and 125m – MUCH more often with standard 125gr .300 Remington rounds than I ever have with 62gr. 5.56 NATOs. And that's about my current max hunting range, so …….

    Neither the AR-15 – and certainly NOT the AK-47 – were ever intended for accuracy our beyond 200m or so. Plus, that's not where the modern-day combat zone is. This is now a close-in, 50-150m kill zone – urban warfare, not jungle love.

    Given that field troops don't have magnified optics (snipers do!), anything beyond 200m is almost in never-never land so why give your position away with a "guess shot". Call in the squad sniper and get it done with a one-timer …

    Same thing with hunting. Who in their right mind shoots at much of anything – with full confidence! – much beyond 200-250m with an AR-15? Dropping a full-grown white tail deer at 250m with an AR-15 is laughable. Besides, you've probably got about 2 seconds – max! – to reach your aiming "decision point" and fire. If you want the kill, you've barely got time to think. For an AK47, you'd be better off sending it to the animal FedEx and then sneaking up on it and using the weapon as a club ….

    If you're not a good enough hunter – or unable to conceal yourself well enough in combat – to get your target within 80-150m in the 21st century, you're in the wrong line of business. You're either gonna end up with no food on the table – or in a body bag.

  • modrifle3

    Interesting comments about the military application of the 300BO. It is my understanding that this round was to be a better alternative in suppressed applications to the 9mm as the 5.56 does not suppress very well. Engagement range is intended to be about the same a 9mm chambered sub with a can. However it gives a longer effective range than the 9mm and at that range a far greater amount of muzzle energy. The idea it would replace the 5.56 as a main battle round is not practical and I think this idea is more publication driven, than AAC driven.

    As for the 7.63 x 39, it is an obsolete round by modern military standards and no issued weapon in this caliber has the same effective range as an equivalent M16 based weapon system. The AK is genrally know to be good to about 300 meters with the M4 up to 500 to 600 meters. The AK-74 was designed around the 5.45×39 to give it an effective range equal to the M16.

  • dougerv

    look for any info on 155gr secnar lapua BC .508 in a 20" barrel 1;11 twist on a Colt M4 Platform ,Power IMR 8208 load data is it possible?

    • Chris

      Try a denser powder longer barrel

  • Kevin
  • guest

    Great discussion, I have to laught because everyone seems to be justifying there chosen round for good reason if its not picked as a military standard prices won't become as affordable. The black out is very appealing it uses readily available components so it doesn't matter what the military decides on they won't be hard to make. The ..223 isn't going anywhere Its a staple round and will join the ranks of the 22lr. If something other then a 300aac variant indeed becomes the next best thing atleast I you only dropped money on a barrel … Not a barrel, bolt and magazines.

    The 30-30 is still a staple hunting round so is the 30-06 which has been fazed out of military use. So it stands to reason that the 300 AAC could be pushed mainstream by sportsmen without the help of the military. Especially by the younger generation of hunters who like the idea of being able to swap a barrel or upper for different game.

  • Fuzzy

    IMHO, everyone is looking for a do-all round. We alreay had it a hundred years ago. .30-06 was jenga in WWII. We used it in bolt guns for snipers (1903s), semis for the blue cords (M1 Garand), squad autos (BAR) and machine guns (Browning 30s). It's been everywhere and done everything. So the guns made for it were heavy, GIs still carried 'em. So it kicked the crap out of you, GIs still shot 'em when the bad guys came a running and they put the bad guy down with authority. Run out of bullets, stick him with the pointy thing on the end or beat him to death with the wooden stock. New fangled whiz bang my aunt fannie. Fahgetaboutit. Bring back grandad's dirty thirty and grow a pair. If you're not man enough for the job, don't take the oath :)

    Before too many people get riled up, the comment above was meant to be tongue in cheek. Just love stirring the pot.

    M60 humping, ground pounding grunt. Infantry in my infancy. Sucks getting old.

  • Wild Bill

    I wonder the differece between the 300 AAA Black with 125 gr. bullet compared to the 223 with 62 gr. steel core bullets. I am looking as to which will give more penetration can anyone help me ut here?

back to top