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Discussion Starter · #1 ·
Just some thoughts on this particular caliber and it’s place in a logical decision-making process. Specifically the thought process of “AR in .223 caliber vs. AR in .300bk caliber”. This is the result of having a discussion with one of my sons on AR-specific calibers; after discussing it at length, I decided to try to put my thoughts to paper.

Full disclosure; my primary ‘serious use’ carbine has long been – and still is – a .223, simply because I already have it on hand, already have it set up exactly as I want it, and already have such a deep stock of ammunition in the caliber. So no .223 hate here at all. I’d trust it for defensive use, I’ve run as many as 1,100 rounds through it in a single day with no failures, and (with careful & intentional ammo seleciton) I’ve even taken deer with the caliber. In a gun with a barrel 16” or longer, in my particular location and situation, the .223 can do just about anything I need a centerfire carbine to do. That said, what follows is my reasoning behind finally accepting the realities of the .300 blackout caliber; originally floated out under the ‘.300 whisper’ name.

I was intrigued by the .300bk long before I took the plunge into it, largely because (as said above) the .223 is pretty good and does pretty much everything I need to do, at least defensively. I’ve been using the AR platform for 40 years now, and have been pretty happy with it in its most-common caliber. But the more I looked into the .300bk, the more its objective advantages became undeniable. Basically, there’s nothing that a gun in .223 can do that a same-size gun in .300bk can’t do. And there are some things that a .300bk gun can do, that a same-size gun in .223 just CAN’T do.

Sticking with a typical carbine with a 16” barrel, a good .223 load will run about 1100-1150 ft/lbs of energy. The same barrel length in .300 blackout will often run 1400 ft/lbs; so substantially more power in the same size package.

Getting into pistol- or SBR-length guns is where the gap between the two calibers really widens, and the .300bk simply leaves the .223 in its wake. This isn’t meant at all as a slam on the .223 caliber; it was just designed sixty years ago to run in a 20” barrel length, and from that length barrel it’s VERY good. But it inherently needs a fair amount of barrel length to get bullets up to the velocities that really lets the caliber flex its muscles. When we get into guns intended to be more compact and maneuverable (ie, SBR’s or pistols), the .223 caliber is just tragically gimped. No fault of its own, because it simply wasn’t designed to be great in that short a barrel. In a 9” barrel, a .223 will typically run 800-850 ft/lbs; where the .300bk will run 1150-1250 or so. That’s a very substantial difference.

If we look at where the two calibers intersect power-wise relative to barrel length, it’s interesting. Briefly put, to equal the power of a 20” .223, the blackout does it with just a 12” or so barrel. And to match the power of a 9” or 10” .300 blackout, a .223 requires a 16” barrel. The difference in handling between a 10” barrel and a 16” barrel is quite noticeable, and if the 16” gun is fitted with a fairly normal 2” muzzle brake or flash hider, it means that adding an 8” suppressor to the .300bk gives the same size package suppressed, as the .223 is while unsuppressed. That’s a major benefit all by itself.

Personal example – my 10” .300bk pistol, wearing the 8” Mystic-X suppressor, has pretty much exactly the same OAL as my 16” .223 carbine, but has the advantage of being suppressed. And pushing the 110-grain V-Max bullet at 2260 fps (giving ~1250 ft/lbs of muzzle energy), it’s actually more powerful than the 16” 223 (almost exactly equaling the power of a full size 20” AR pushing a typical 55-grain bullet). So same overall length as my 16” AR, suppressed blast, and increased power, all at once. Added together, those make for kind of a big advantage imo.


Now, to be fair and objective, the .300bk – just by virtue of using a more substantial .30-caliber bullet – does have an inherent disadvantage in the ammo-weight department. The bullets are bigger and naturally weigh more. How big a deal this is, is a matter of personal comfort zone. The weight difference between an AR magazine loaded with 28 rounds of the 110-grain .300bk ammo that I use, vs. loaded with 28 rounds of standard-issue 62-grain 556 ammo, is a mere 3.07 ounces. So in my world, that amount of difference is irrelevant. I’m not a Navy SEAL or Delta Force operator, and I’m never going to be “going into action” with rows & rows of magazines on my chest or belt. Nor am I going to be humping all my life-support gear on my person long distances as I did when a young infantryman 40 years ago. I’m a private citizen, and I’m unaware of any incident in the USA where a private citizen went through even one entire rifle magazine in a defensive shooting situation. But let’s say I’m terrifically paranoid and carry three rifle magazines – that means a total difference of nine ounces. And boys & girls, if nine ounces makes the difference in whether or not a rifle setup works for me, I need to put down the rifle and pick up some dumbbells. So for all intents & purposes, in any situation that a private citizen in the USA is liable to face, the trifling ammo-weight difference is simply a non-issue; at least if you’re a grownup.

The .300bk does have a less flat-shooting trajectory than the .223 does; again just due to using a more substantial bullet. What the .300bk drops at 275 yards, the 223 doesn’t drop down to until about 320-340 yards. So you do gain about 20% in mpbr distance with the 223 over the 300bk. That’s undeniable, but imo, again pretty irrelevant. I’m never going to be doing any defensive shooting at 300 yards; ymmv. And for hunting purposes, at 300 yard distances neither caliber is a particularly good choice.
 
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Discussion Starter · #2 ·
Continued –

All of the above is strictly dealing with full-power, rifle-level loadings. The .300bk has even greater advantages if a person wanted to get into extremely quiet suppressed shooting; at least quiet suppressed shooting of anything other than paper targets.

One neat quirk of the .223 caliber is that it shares the bore diameter of the .22LR round, allowing the making of adapter kits that can let you shoot the cheaper rimfire round in your full-size gun. These are pretty handy and I’ve owned several of the .22LR adapter kits; for both .223 AR’s and for some other guns as well.

As with most things, “there’s no such thing as a free lunch” when it comes to the rimfire adapter kits. They have quirks of their own, including the quirks inherent in the .22 rimfire caliber itself. On the AR rimfire kits, the only one I’ve owned is a Ciener, that I’ve had since at least 2002, maybe longer. It’s a neat accessory to the gun and once you find ammo that it likes (as with any rimfire firearm), it can be fun and a handy trainer for new shooters. I’ve even taken small game with it out to probably 50 yards or so; it does okay with the loads it likes, especially remington’s 38-grain subsonic HP load. It also makes for a very quiet shooter if you use reduced-power subsonic ammunition and put a suppressor on it.


But on the topic of the .300bk, let’s compare the performance of the rimfire adapters shooting subsonic ammunition to the performance of subsonic .300bk ammunition.

Power – no contest. The one subsonic load that my Ciener runs pretty reliably with is the remington mentioned above. Its 38-grain bullet at 1024fps (measured from my gun’s 16” barrel) is putting out 88 ft/lbs of energy. You can get more powerful loads, but most of them will be faster than subsonic velocity, so you lose the quietness of a suppressed subsonic round. There is one that should do better, the Aguila 60-grain subsonic loading, but my ciener kit won’t reliably run it. Some probably will, but I can only speak to personal experience and mine won’t. It’s a little strange in that when the Ciener unit was new, it ran fairly okay with the Aguila 60-grain stuff, but as it broke in and got more reliable with some other loads, it got less reliable with that one extra-heavy-bullet load. Don’t know why exactly, but it’s actually less reliable with that load now than it originally was.

But even if the 60-grain load runs fine in your adapter kit, it’s still limited to around 120 ft/lbs or so, with it’s claimed 950 fps velocity. Compared to a factory-available 220-grain subsonic load in the .300bk, you easily get five times the power of the 38-grain load that my Ciener unit likes. And even if your Ciener unit likes the extra-heavy Aguila 60-grain load, the .300bk still buries it at about four times the power. Basically, power-wise, a subsonic .300bk load roughly duplicates the energy of a full-house .45acp load, and that hugely beats any .22 rimfire running at subsonic speeds.

Ease of conversion from full-power to quiet subsonic ammo – the Ciener and similar units swap fairly easily in & out of an AR rifle. You remove the .223 magazine, open the rifle at the hinge point, pull out the bolt carrier group, install the Ciener bolt assembly into the AR upper, close the AR at the hinge point, and insert the Ciener magazine. Obviously this also involves retrieving the Ciener unit from whatever pouch or pocket it was riding in, and stowing the normal AR bcg when you remove it. Not a huge deal, but something that needs doing.

To do the conversion on a .300bk gun, the process is as follows: you remove magazine containing full-power ammo, and insert the magazine containing subsonic ammo. That’s it. No spare parts to retrieve or stow away, and no proprietary magazines.

If your gun can chamber full rifle-power ammo, it can also – instantly – chamber and fire the subsonic ammo. No rimfire adapter or conversion kit that I’m aware of can do that.

So if we’re using subsonic ammunition, the .300bk has every advantage that we can list, with the exception of ammunition cost and weight. As with the ammo-weight issue mentioned above, I contend that for real-world, private-citizen use it’s an absolute non-issue. A private citizen doesn’t need to carry large quantities of loaded magazines. Apocalyptic wet dreams aside, we simply don’t. I’d even go so far as to say that for American law enforcement officer use, it’s still a non-issue for them as well. (At least, it better be – if a cop can’t use .300bk subsonics because they weigh more than .22LR ammunition, I contend that he shouldn’t be firing a gun in public to begin with.)


Overview on the two calibers – In some instances, the .223 absolutely has advantages over 300bk. If you’re in a situation where you’re going to be shooting a whole lot of ammo in a day such as a training class or whatever, the cheaper 223 ammo could be a welcome thing.

If you’re a soldier humping large quantities of ammo on your person over long distances, the saving of a few ounces per magazine could be a bonus. But for a private citizen in modern America, that’s just not the case.

And if I were going to be shooting out hundreds of yards, the flatter trajectory of the .223 could have advantages in certain circumstances. Personally, I’m not going to be doing that, and I still maintain that if you are doing that (especially for hunting purposes) that neither one of these calibers should probably be your first choice anyway.

In the process of genuinely trying to come up with advantages of .223 over .300bk in similar AR platforms, those were the only three circumstances I could think of where the 223 wins over the .300bk caliber. If there are others that I’ve missed, I’d not mind at all hearing about them.
 
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And another thing that's interesting to the hand loader.
First the cartridge case can be formed from .223/5.56 brass.
But also and important to me is that it can be loaded with almost any weight .308 diameter bullet from 110 to 225gr.
Once I get my upper receiver in .300BO put together I'll have 4 different cartridges that can be loaded with almost identical bullets. If I wasn't concerned about optimum performance from all 4.
Technically I could run one bullet in the 150gr to 168gr rang in them. Talking .300BO, .308Win., .30-'06 and .300WM.

BUT I won't.
I like to optimize firearm and ammunition for use.
However, I am going to try out the Hornady 225gr ELD Match in the .300BO.
I'm going with that as I'm interested in a primarily suppressed upper receiver.
Or the very least something not as obnoxiously loud as a shorty 5.56 and going to work with it some with that blast can I lucked out finding.
So I'll just say that for setting up a lightweight and compact package that can sling out 225gr bullets that have superior ballistics to a subsonic .45acp load of similar weight that it fits my needs.
The 225gr ELD is what I currently have tweaked for my prospective long range .300WM competition load.
 

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Discussion Starter · #5 · (Edited)
Ed - Very good point about the abundance of .308" bullet choices for loading the caliber. I don't reload the .300bk yet, but you can get bullets for maximizing penetration, for minimizing penetration, thick-jacketed enough for hog & other medium game, or thin jackets enough for small animals. One thing that struck me when I first started looking into it seriously, was how well some bullets perform in the .300bk for the roles of defensive and hunting use, that were intended for varmints in bigger calibers. The 110 V-Max and 110 Varmageddon make for very shallow-penetrating performance at the higher velocities of the .308, .30-06, etc. But at the lower .300bk velocities, they perform very well for larger animals. The bottom track in the gel block below is the 110 V-Max:

Rectangle Font Line Heat Slope

For personal defensive use and nuisance animals, that's about ideal imo.


Fwiw, the unsuppressed 16" 223 next to the suppressed 10" .300bk:
Air gun Trigger Gun barrel Wood Machine gun
 
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John- There's one bullet I'd like to try out well two actually. Both are 125gr and I've used one extensively in .308Win. That one is the SPEER "TNT" Varmint bullet. The next one is the Nosler Ballistic tip just because it's a boat tail design. And in theory ought to have a hair bit better trajectory.
But that is going to be dependant on what I can get to try out when the time comes.
 

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I'm very impressed regarding everything that I have read or watched on the ,300 Blackout. That being said, after looking at the collection of firearms I currently have, I'm having a hard time seeing what it would accomplish, that firearms that I already own can't do.
 

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Discussion Starter · #8 ·
I'm very impressed regarding everything that I have read or watched on the ,300 Blackout. That being said, after looking at the collection of firearms I currently have, I'm having a hard time seeing what it would accomplish, that firearms that I already own can't do.
That's similar to my thoughts on it as well. With so many years invested in .223, I doubt it'll become my primary. But if I were starting out from scratch, I'd probably do the reverse - have the .300bk as primary for defensive and hunting use, and have a spare gun (or just spare upper) in .223 for the sole purpose of cheaper ammo when taking a class or something.

I really like the compactness advantage of the blackout; getting the same power as my 16" carbine, but in a much shorter 10" package. Similarly, for hunting purposes - a 16" gun giving me the power of a much-longer 24" .223 gun.
 

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Yep, I'm going to end up with a pistol with two uppers and or two separate AR Pistols.
I've a friend in the Tulsa Oklahoma area who's going to be offered the upper to. Or the whole gun if he can get it transferred to him.
I've got a decent variety of AR type firearms I'm trying not to get an over abundance of them.
 

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Discussion Starter · #10 ·
Found a couple comparison charts of .223 vs. .300bk at various barrel lengths. (The second one is in Joules rather than the ft/lbs we're more used to, but the ratios are the same.)
Font Material property Parallel Rectangle Pattern



Rectangle Slope Plot Font Line

This more vividly shows the difference in power, especially from short barrels. Notice that to match the power of the M4 carbine's 14.5" barrel, the .300bk needs only a 9" barrel. And in SBR applications, a stubby 7" gun in .300bk actually exceeds a 10.5" or 11" .223 gun.

At my stage of life, I'm not going to start all over with a new caliber. This is just something I'm factoring in, using the .300bk to augment the .223 that I've been so heavily invested in for so long. But if I were young or just starting out, it would definitely push me into using the .300bk as my primary choice. Other than ammo cost, I haven't found any advantage that the .223 has over it.
 
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I know one thing I'll be adding that powder to my look for list.
I used to use it for .357magnum with a identical bullet weigh and a similar charge of powder.
Of course the profile & B.C. of the bullet was totally different 😁
 
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