Converting a .223 to a .300 Blackout in 2 Easy Steps: Part 2

300_blackout_blk_subsonic_rifle_aimpoint_silencerco_supressorContinuing the brief saga of changing over an ordinary gas impingement .223 AR15 into a .300 Blackout, we will complete the barrel change, add a free floating handguard, screw on a can, add the necessary accessories to bring the gun up to our survivalist standard, and head outdoors.  Look, I get it. There is no shortage of irony about a rifle that rivals a compound bow in hunting prowess. I hunt with a bow, and while a 50 yard shot is still something on the edge of my comfort zone, a 50-yard subsonic .300 Blackout shot is acceptable. But the more I thought about it, the more I considered blending grizzly bear shotgun wisdom with 300 BLK hunting. There is no rule that says you cannot run both subsonic and supersonic ammo in the same mag. So imagine whitetail deer hunting in thick brush with the first round or two being subsonic and the rest being supersonic. Being a semi-auto AR-platform rifle, I imagine that the second shot could happen almost instantly, but if the target is on the move, all subsonic bets are off and sending any necessary rounds further downrange should be expected. Noise is not the problem now. Range and accuracy is.

By Doc Montana, a contributing author of Survival Cache and SHTFBlog

Since my testbed AR had an A2 front sight post pinned to the .223 barrel, I took the opportunity to upgrade from the no-frills Magpul MOE handguard to a Midwest Industries free floating M-Lock aluminium handguard about nine inches long. The Midwest Industries handguards come in various lengths and attachment platforms. A detail I really appreciated was the five quick-detach ports; three up front, and two back by the receiver.

Related: Magpul Armorer’s Wrench

As the .223 barrel had an A2 front sight, I chose to abandon it and install a Yankee Hill mini gas block inside the free floating handguard. Since I’ll be running an optic on the top rail, I opted for some Magpul MBUS Pro Offset sights for backup and for longer distance shots. By the way, if you are wondering the difference between a handguard and a forend, the particular part name has to do with whether or not the specific piece of furniture is just for support or to protect your hand from burns. In the case of the AR platform, it is a handguard.

Wide Receivers

Instead of swapping barrels, many of the Blackout-curious type will just buy or build an entire upper dedicated to the 300 BLK and switch out the whole upstairs, sights and all. In my case, I was not excited about the DPMS AR 15 as a .223 in the first place, and don’t mind making a dedicated Blackout gun. Plus, if your luck holds, you will have nothing more the cost of a barrel which is considerably less than an entire upper. And there is that in-between option where bolt and charging handle jump back and forth between calibers.

Magazine Subscriptions

As I noted in Part 1, there can be no mistakes with ammo. There is a chance that a .300 Blackout round can cycle into a .223 barrel to the point where it will fire upon a trigger pull. The results of such a mistake can be devastating to both shooter and gun.

300_blackout_blk_rifle_with_supressor_silencer_outdoors_huntingBut there is another factor that needs to be kept in mind and that is that 300 BLK ammo is widely available over the gun counter in both supersonic and subsonic varieties. And in some cases such as hunting, the shooter may want to switch between supersonic and subsonic on the fly. In my case, I will run two 10 round oranged-colored Magpul Pmag magazines while hunting. One is filled with my subsonic loads and the other with supersonic ones. That way I can carry subsonic for close range brush situations, but if something farther away presents itself, I can eject the subsonic mag, cycle out the chambered round if there is one, and then reload with a mag full of supersonic cartridges.

To keep my two Magpul 10-round orange hunting magazines separated I changed one key feature. I run a black baseplate on the supersonic package and keep the matching orange-colored one on the subsonic. Why that combo? I decided that if I’m needing subsonic in a darkness situation (not necessarily hunting) I need to know with certainty that I have the subsonic mag. If I have a black base plate, it will appear a black or not there under minor light.

On a lighter note, for more fun I use Magpul’s sand colored 30 round Pmags. But as mentioned before, the cost of ammo being what it is makes blasting 300 BLK round after .300 Blackout round downrange is questionably cost prohibitive. But in a nutshell, all my Magpul sand colored mags are .300 Blackout only. And I never run a orange-colored mag for .223/5/56. Never.

No Mr. Bond, I expect you to “dye.”

300_blackout_blk_rifle_with_supressor_silencer_outdoors_orange_dye_mapgul_sandThe Magpul’s sand colored mags were never expected to remain sand colored, but dyed into another color the user prefers. With that in mind, I decided to drop some sand-colored magazines into RIT dye and see what happens. Since the dye color is totally up to the dyer, anything on the rainbow is fair game with camo and combinations also a possibility. Due to the mess of dying something, I picked up a pot at the Goodwill and laid out tinfoil around the stove and counter. With about two quarts of boiling water in my pot, I dropped in the gutted mags (springs and followers removed) into the pot and stirred them around for 10 minutes. The dye set rapidly, but then slowly got darker. I ended up using about a third of the bottle of RIT dye. After another 10 minutes in a warm freshwater rinse and thorough drying, the mags were reassembled and good-to-go.

Switch Hitter

300_blackout_blk_subsonic_aimpoint_rail_barrel_swapThe ability to interchangeably run both supersonic and subsonic round through the same gun with the same bolt is truly revolutionary. But the ballistics don’t follow the same rules. So to be able to run either/or subsonic/supersonic rounds at whim means that you need keep your .300 ducks in a row, as well as your sights. There is little similarity between the subsonic and supersonic trajectories so you will either need to memorize ballistics tables as well as know which round your sights are zeroed for. Or you can run dual sights. Luckily the limited range of the 300 BLK is something that iron sights can handle no matter the bullet weight. Sure, a 6x optic will give you an accuracy advantage, but any good shooter can squeeze off plenty of precision whether iron or glass.

Considering that I am using “hunting” as a euphemism for…whatever, I am interested in two no-brainer sighting solutions; one for supersonic and one for subsonic. Since I have many other longer range battle-ready options so maximizing the .300 Blackout’s long distance capabilities is not really all that practical when taking the long view. To justify the 300 BLK in a survivalist arsenal, one must maximize its strengths and minimize its weaknesses.

Read Also: Survival Debate: Aimpoint vs. EOTech?

On this particular build, I zeroed the Aimpoint H1 for the subsonic bullets at 50 yards, and zeroed the Magpul MBUS Pro Offset sights with the point of impact for supersonic bullets at 150 yards. Of note is that the stock front post has been replaced with Magpul’s MBUS Pro Enhanced Front Sight Post, a tiny screw-in after-market post that improves accuracy by reducing post thickness. There is a stark contrast between sub and supersonic bullet drops. Flying below the speed of sound, a zeroed-at-50 220 grain bullet will drop almost 15 inches at 150 yards, and about 70 inches at 250 yards. Yes, the bullet drops almost six feet! While a supersonic round zeroed at 150 yards will be an inch high at 50 yards, and less than a foot low at 250 yards. So you can see that the use of two independent sighting platforms is worth the effort.

Related: Trick Out A Cheap AR15

Taking that sighting duality a step further, the option of running both subsonic and supersonic ammo in the same magazine. I can imagine where the first or top round or two are subsonic followed by the supersonic ones. This concept is not new. A popular 12-gauge shotgun option here in bear country is to load the tube rotating between double-ought buckshot followed by slugs. And fans of the Taurus Judge handgun have been known to run alternating .45 Long Colts and .410 shotgun shells in their five-round cylinder.

Quiet down there!

300_blackout_blk_111_decibel_sound_meterRunning a suppressor on a subsonic .300 Blackout makes for an interesting option in survival/prepper guns. Although the 300 BLK has distance limits, the radius of effectiveness is up to you. And that is exactly why I turned one of my AR15s into a .300 Blackout and so should you. In my testing, the 300 BLK running subsonic was not all that quiet. Certainly hearing safe, but much like a tiny firecracker going off. Anyone 50 yards away would probably ignore the sound if they even heard it, but closer up, there is definitely something going on. Of course I was in a very quiet area with little more than a slight breeze and a few birds disturbing the peace. Supersonic loads were a different story. Even through the silencer, they were still a pretty good crack.

My audio testing equipment produced numbers in the 120 dB range for supersonic bullets exiting through the Omega suppressor, and 111 dB for subsonic rounds. A 95 dB sound is like a New York Subway, or public bathroom hand dryer, so 111 is not excessive, but certainly not silent. Popping off a couple subsonic rounds in a confined space will still make your ears ring for a moment or two.

300_blackout_blk_subsonic_supressor_scilencer_omega_scilencercoI replaced the classic “bird cage” flash hider with a SilencerCo ASR Muzzle Brake. Not to tame any massive recoil, but that it works as a fast attachment mount to the Omega silencer. The ASR does add a bit more weight at the far end of the barrel, and healthy bite into the deep end of your wallet, but it works great. Just don’t forget, as I did, that it also requires the ASR mount on the silencer which will not screw directly onto a barrel. You need to swap out supressor end caps to make the silencer compatible with your mounting system. I grabbed my Omega and bolt gun for a quick hunt only to discover I still had my ASR mount on the suppressor, but I actually count myself lucky to be able to have a problem like that.

Blackout Reloaded

The AK 47 round of 7.62 by 39 is actually a little larger than 30 caliber, about .311 compared to .308 to be more exact) meaning the bullet choices for reloading a 300 BLK are as varied as any other popular 30 cal including the .308 and 30-06. Further, a .223 case can be converted into a .300 Blackout case with a little retooling. Enough so that many 300 BLK aficionados are hitting up their .223/5.56 friends for their brass.

Of course there is also the SHTF component to having any particular gun. Bugging in is an obvious use for a quiet rifle. But bugging out is a total no-brainer. Survival of the Fittest is a popular saying that, unfortunately, is backwards. In order to know fitness, you need to know who survived. So really it is that those who survive have the right fitness. But no matter how you slice this cake, doing anything with less noise is fitness. Lobbing 30-cal lead without blowing out your eardrums is more practical than you can imagine.

Brass Tacks

300_blackout_blk_headstampsThe first outing with the 300 BLK took place out in the sticks of Montana. I found a place up in the mountains where I could set up my gear in the trees providing a safe shooting area. After a couple hours, I spent some time picking up my brass. I noticed how far and what direction the brass flew. Back home, I was inspecting the brass under a magnifying glass to look for any features or scarring that might indicate problems with the gun. Imagine my surprise when I realized I was holding .300 Blackout brass that was not from my gun. The first indication was a different brand headstamped on the case. Further, some of the same-branded shells were too weathered to have been shot that day, as well there a few with bent throats and dinged case mouths. So there are like minds out there.

The Sound of Silence

I used the first hunting trip with this gun to test its practicality and shake out any concerns. When fixated on quiet, every little click or squeak is loud. The clicks came from my Magpul stock. It is the base model with no way to lock down the extension setting. And the squeak came from both the Magpul MS-3 sling and the  Blackhawk Quick Detach clip I used up front on the Midwest Industries free-float handguard.

In the end, this exploration of the 300 BLK has shown promise, but also a full plate of limitations that will keep it off my shortlist of bug out gear. When facing a significant unknown, my first gun to grab would be my Katrina Rifle, and a close second would be my Katrina Pistol. Third would be my Bug Out Long Term (B.O.L.T.) .22 pistol. A Bug Out BUG (back up gun) might be fourth, and then probably a long range rifle like a 30-06 would round out the first five. So a .300 Blackout would be somewhere between six and 10 along with a Project Squirrel gun.

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8 comments… add one
  • Nailbanger January 11, 2017, 9:53 pm

    Personally i like just building a complete upper, can change stuff around real quick that way, the vast selection of custom parts is astounding, some real nice stuff, recently built a new upper for one of my rifles, just a plain old 223 wild, but with the match grade barrel and some other goodies it turned a cheap lower into a nail driver at 200 yards plus when coupled with home rolled ammo, truly a sporting rifle regardless of what the libtards say

  • Drew January 12, 2017, 5:43 am

    Nice, I was wondering when part two was coming out. I’ve been budgeting a suppressed build for later this year, and the .300 BLK vs. 9mm or .45ACP debate is still raging on in my mind. I need another caliber in the arsenal like I need another hole in my head, but its niche can’t be denied.

  • Doc Montana January 12, 2017, 10:55 am

    Hi Drew,

    I think the BLK has arrived. Why? Because Magpul has announced a new .300 Blackout 30 round magazine. It is specially designed for the 300 BLK and to avoid mixing ammo.

    Unlike the pistol cartridges you mentioned, the BLK has some rifle energy so ballistics are not equal. Plus you can go full speed ahead on a dime turning your quiet riot into a “real” gun.

    But I too am running out of places in my head to put new holes.

  • Nick January 13, 2017, 10:38 pm

    How to convert a .223 to 300BLK:
    -Buy a 300BLK upper for 300$ and snap it on. Go have fun.

    • Doc Montana January 15, 2017, 11:49 am

      Hi Nick

      I find fun in the journey, not just the destination. And by nature I like to tinker and break things in order to learn how they all work.

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  • gagnant the voice February 7, 2017, 9:55 am

    Après avoir déambulée dans les couloirs sombres des catacombes
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  • Old frog February 7, 2017, 7:28 pm

    GI BRASSLOCKER 812.952.1222 is good source for 300bk brass has treated me well. Have bought thousads of rds from them. Good people. Now if I could find a good supply of bullets? Any ideas? Got my built up uppers from CDNN down in Texas,takes a little to get use to the blackout. Like 125hp high V for very day use here at the ranch. Shoots like my old 30/30


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