556 vs 300blk in pistol configuration

Disgruntled Seabee

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Someone skool me in the pros and cons of 556 vs 300blk in an AR pistol. I'm going to make one, most likely 556, but have seen a lot in 300blk and am wondering what, if anything, would make it a better choice.
 
Im sure the experts will chime in but when I researched this I found really anything shorter than a 10.5 barrel youd be better with 300blk because of ballistics. Also muzzle blast and suppressor option is much better with the 300. I went with a 10.5 5.56 and am very happy with it, and can always just throw on any upper to convert.
 
As mentioned above...
As far as ballistics
<10.5 inches go with .300
>10.5 inches go with 5.56/223

Though, realistically, even at the speeds you get out of a 5.56 under 10.5 inches it will be pretty darn devastating to anything/anyone under 100 yards. I love everything about .300 AAC except the price of the ammo.
 
As mentioned above...
As far as ballistics
<10.5 inches go with .300
>10.5 inches go with 5.56/223

Though, realistically, even at the speeds you get out of a 5.56 under 10.5 inches it will be pretty darn devastating to anything/anyone under 100 yards. I love everything about .300 AAC except the price of the ammo.
That's the only thing that's really holding me back from 300 is the price of ammo.
 
That's the only thing that's really holding me back from 300 is the price of ammo.

And it is a real issue...most people who shoot it a lot get into reloading, so barring that you are at minimum looking at .37-.40$ per round (usually reman stuff), where as .223 is going to be about .17 per round for plinking stuff. So stockpiling enough for a long haul is more difficult.

Another main reason people go with .300AAC is because it is easy to slow the bullet down to get to sub-sonic speeds for adding cans.

So...I guess in short...if you are wanting to add a can, or don't mind paying a premium for ammo then .300 is the way to go. If you just want something that is fun to shoot, still accurate and packs more punch than a pistol at <100 yards then go with the 5.56.

Again, don't get me wrong, the .300AAC is a hoot to shoot. Its a real thumper and has a much different recoil impulse than .223. Reminds me more of the push of an AK than the snap of an AR. And under 100 or so yards I like the bullet size. But you have to ask yourself, are those enough of a tradeoff over 5.56 to make it worth it.

(Also...if you don't like it...just sell the upper, replace with 5.56 and carry on...)
 
Sorry bro, my wife got me distracted lol i read your very thorough post, and I considered a lot of things in it especially the muzzle velocity of 556 out of particular barrel lengths. I think I'm going to go with a 12" version of my gas piston. I like how it operates and it's 1:7 so it'll still give good velocity to the bullet. Thoughts? @Michael458
 
I have 10.5" pistols set up identically in 5.56 and .300BLK. Plink and train with the 5.56 the .300 is for social work.
 
I may will eventually move to 300blk I just don't have the money for a "decent" amount of ammo, and by decent I mean at least 2k rounds. With .40c being the average for the "good" stuff that's $800+ and I just can't do it right now. Eventually, absolutely, been wanting to for a bit. I don't feel like getting random 20rd boxes here and there either. Plus I gotta get my rifle skills back up to par.
 
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I may will eventually move to 300blk I just don't have the money for a "decent" amount of ammo, and by decent I mean at least 2k rounds. With .40c being the average for the "good" stuff that's $800+ and I just can't do it right now. Eventually, absolutely, been wanting to for a bit. I don't feel like getting random 20rd boxes here and there either. Plus I gotta get my rifle skills back up to par.

I’ll play devils advocate here...

I say go for it: you don’t >need< 2,000 rounds on hand. At least not all at once.

I’ll explain...because I have time and feel like playing the “what if game”.

This .300AAC you are putting together is a truck gun. It is meant to be the gun you grab when things go south. So what are the main scenarios you would need it:

1. Immediate pew pew/active shooter/self defense: a full military combat load is like 200-300 rounds...so, just keep 10 mags loaded and in a gear bag in the car.

2. SHTF get home Gun: as above...with your get home bag and everything you will have 10 mags in the car, so carry whatever you want to get home. Once home, if it is truly a SHTF scenario, then grab your ballistically superior full sized AR for social work. This pistol is meant to be stop gap between pistol and rifle. Not a replacement for them.

Practice? Shoot it enough to ensure zero, ensure reliability, and then practice with your cheaper 5.55/223. It’s the same as carrying .357 magnum and practicing with .38 special. The platforms are going to be identical in their manual of arms.

So...start off with 300 rounds...get your 10 stocked up, and then from there just replace what you shoot and buy more when you feel like it.

Personally, I really only keep 4 dedicated .300 AAC mags loaded. I am too fat to be firing and maneuvering for too long, so I have no illusions of surviving a long lasting running gun battle. And if it happens at home, I have other options.


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I’ll play devils advocate here...

I say go for it: you don’t >need< 2,000 rounds on hand. At least not all at once.

I’ll explain...because I have time and feel like playing the “what if game”.

This .300AAC you are putting together is a truck gun. It is meant to be the gun you grab when things go south. So what are the main scenarios you would need it:

1. Immediate pew pew/active shooter/self defense: a full military combat load is like 200-300 rounds...so, just keep 10 mags loaded and in a gear bag in the car.

2. SHTF get home Gun: as above...with your get home bag and everything you will have 10 mags in the car, so carry whatever you want to get home. Once home, if it is truly a SHTF scenario, then grab your ballistically superior full sized AR for social work. This pistol is meant to be stop gap between pistol and rifle. Not a replacement for them.

Practice? Shoot it enough to ensure zero, ensure reliability, and then practice with your cheaper 5.55/223. It’s the same as carrying .357 magnum and practicing with .38 special. The platforms are going to be identical in their manual of arms.

So...start off with 300 rounds...get your 10 stocked up, and then from there just replace what you shoot and buy more when you feel like it.

Personally, I really only keep 4 dedicated .300 AAC mags loaded. I am too fat to be firing and maneuvering for too long, so I have no illusions of surviving a long lasting running gun battle. And if it happens at home, I have other options.


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My trunk gun has a 20 round mag in it and 4 30s with it. Im not looking for a fight but looking to get out of one and get home.
 
Sorry bro, my wife got me distracted lol i read your very thorough post, and I considered a lot of things in it especially the muzzle velocity of 556 out of particular barrel lengths. I think I'm going to go with a 12" version of my gas piston. I like how it operates and it's 1:7 so it'll still give good velocity to the bullet. Thoughts? @Michael458

Gotta luv it when your wife distracts you huh? :p
 
I chose 556 simply because of ammo cost. I shoot a lot out back and I like my black guns.
And I like the wee 7" barrel too. I knew ballistics were gonna suck, (comparatively) but I chose to go more 'pistol' than go for superior ballistics. I don't hunt, I built it to be a 50 yard gun and it does that real well.
 
2200fps out of a 7.5 barrel with a 55gr soft point will penetrate level IIIA armor, and expand while doing so......arguably better than the FN 5.7x28 round from the P90 sub gun, and still holds 30+ rounds. Mine is pretty neat with the D60 Magpul drum since it fits nicely in a gym bag, etc.

stolen shameless from Hunter @ Rangehot.com

SBR-7.5-inch-barrel.jpg


Certainly more effective than any normal non-magnum pistol round.
 
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Best thing I can convey to any of you, or anyone, Hand Load, make the investment to do so, it opens up an entire World Of Performance for you................
 
...handloading...aint yet met a ruffian worth my time and effort for a handload...best they deserve is Tula...maybe Wolf if Ima feelin generous...
 
HEH....... Well, that is a point. Just feed them a lot of them to equal one of mine........! That's how I figure it. Ain't math good!

I will stand with Handloading for anything worth feeding in my stuff..........

Of course, I love hand loading ammo, so you gotta love it. And, it don't have anything to do with being cheaper, its more expensive...........

I use Processed Brass from Everglades

This 5.56 Processed Military Brass is fully processed. Cleaned, resized, deprimed, swaged and trimmed. Ready to load. Brass is once fired military auction brass in excellent condition. Appears to be predominantly Lake City and FC. $265 per 2500 pieces or .106 each........

50 Raptor Cutting Edge $56/50..... but I buy BULK, and I get a hell of a discount because I helped design it........I believe the last 2500 I bought were around $0.80 each........

That is basically $0.90 each without the powder/primer..............

Roughly the 300 BLK is about the same...........

But I know without any doubt at all, it is #1 top of the list in Terminal Performance in that cartridge.

Now one does not need several 1000 of these on hand unless you are totally OCD like me. You can get by with far less and then go to other bullets for bulk, but FMJ is not hitting on much of anything.... Have to use a lot of those to equal up..........

Oh, no doubt bud. I was just messin with ya. I load my own at times too. But not as much since family life has gotten so hectic. In the mean time, Ill choot em with the best I can buy. Except carnies...carnies get tulammo.
 
Built a 10.3 in 5.56 a few months ago. So far, I’m really pleased with it. I’m in the process of doing some handload r&d...just gotta get a chrono to test what I have loaded.
 
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