Greetings to all out there. I have a question, and am looking to get responses about 5.56 snd 300 Blackout. First let me say, although I know just enough about certain rifles, and normally my go to is the basic AR15 5.56 Nato, but am wondering, although I know that the 300 blackout, for lack of better terminology, packs a bigger punch then 5.56, which may or may or may not lead to greater recoil, what’s other’s thoughts on using the 300 BO, as the main rifle, that one would use more continuously and shoot a lot of, as one would normally shoot a lot of 5.56? I hope that all makes sense, what I’m asking. Thanks ahead of time for any and all responses!
2 Likes
My humble opinion only: If I were going to go to .30 cal I’d go .308.
5 Likes
Please forgive my ignorance, 30 cal? I know 300 BO is basicly 7.62 so where does the 30 cal come in at?
2 Likes
Stick with the common calibers, 5.56, .308, .30-30, .30-06 and on and on. 
Price and availability. Although all are stupidly expensive right now. 
P.S. Welcome back. 
3 Likes
Same diameter bullet. .300 is three hundred of one thousandth of an inch. .30 is thirty one-hundredths of an inch. Same same.
3 Likes
308 is an AR10 though, right?
2 Likes
Yes. It is.
OK, thanks, much appreciated!
2 Likes
Soo, to my understanding .300BLK was designed to match the older and more ballistically efficient 7.62x39 (AK-47/SKS round)
The standard m193 55grain 5.56x45 round is flatter shooting and faster to target, however is somewhat less effective against barriers and body armor than the 7.62x39
So to compensate for that the .300blk was designed based off of the nato 5.56 round and weapons platforms.
It’s for all intent and purpose, a 5.56 case that’s cut down and necked to .30 caliber with a far heavier bullet loaded in and a slightly different powder charge.
As to the difference in recoil,… I don’t personally own a .300blk rifle, though I have shot a couple… it basically felt the same as the 5.56. Or any AK/SKS 7.62x39 platform I’ve shot.
Now, the AR-10 platform is a totally different beast! .308 or 7.62x51 same diameter bullet, MUCH larger powder charge.
6 Likes
“Bigger punch” is an understatement. A guy at my range chambered a round of 300 BO in his AR and literally blew it apart. Lucky to have survived.
3 Likes
300 Blackout ammo ranges from about 500 to 1,400 ft-lbs of muzzle energy vs. about 1,200 to 1,400 ft-lbs for 5.56.
Technically the only difference between a 300BLK and 5.56 AR15 is the barrel. So, you can convert one to the other with a barrel swap using one AR upper, or, more expensive, but easier, have a complete 300BLK upper and a 5.56 upper. At that point you may as well buy another lower and have one of each
The danger pointed out is you can chamber a 300BLK cartridge into a 5.56 barrel. This is very dangerous because the bigger 300BLK bullet will not go through the smaller 5.56 barrel. If lucky only the gun will be destroyed. I put labels on both the upper and magazines to be sure I don’t do that.
The lower, basically pistol power 300BLK ammo is quieter (especially suppressed) and good for close quarters. The higher power ammo punches a bigger hole with a heavier bullet than 5.56.
It’s kind of similar to the faster, lighter 9mm to slower, heavier 45ACP arguments 
4 Likes
The 300 blackout was designed for improved performance with short barrels and sub-sonic, suppressed, rifles. With sub-sonic rounds, short barrel, and a suppressor it is a superior setup for home defense. The .300 BLK reaches peak ballistic potential from a 9-inch barrel, again, making it ideal as a short barrel home defense weapon.
Edit to add: Bottom line is, what is “better" depends on the intended purpose.
7 Likes
…what Will_B said.
2 Likes
This is the danger of .300blk!
It is the same casing and over all length as a standard 5.56 round!
It uses the exact same magazine, and will feed into the chamber of a 5.56 gun….
However, a .30 caliber bullet won’t go down a .22 caliber barrel… and you get a violent explosion!
5 Likes
agreed. .308 is the best all around cartridge there is IMO.
6 Likes
Thanks all for the info. If I’d go to a 308, need an AR10 lower, so, am thinking my shopping list might get a bit longer, lol.
6 Likes
I would have to agree. Especially if planning to hunt pretty much any game available in the U.S. The AR10 is a much heavier weapon, though, and it definitely has a lot more recoil than an AR15, 5.56.
2 Likes
The 300BLK shoots the same exact bullets as a 308, just slower.
As far as I know, 300BLK, 308, 30-06, 300 WIN-Mag, and I’m sure many others all shoot 0.308 diameter bullets. Please correct me if I am wrong …
I’ve read there can be feeding issues with the larger, heavier 300BLK bullets when loaded in 5.56 magzines. I have not spent the money to experiment to find out, I bought 300BLK specific magazines …
3 Likes
Yes, although there’s still some things I need to learn and am learning, 308 is one of those so called “Thumpers”. Definitely need AR10 lower if getting a 308 upper. Oh look, a sale on 308 uppers, lol.
4 Likes
Yes, but there are vast differences between the 300BLK and .308 rounds.
3 Likes