I was reading a little bit about the 300 blackout and I'm kind of digging the round. I've been wanting to do another build and I'm torn between the 300 blackout and just doing another 556. What are your thoughts and pros/cons. I've talked to a couple close friends and one says go with 300 and one says stay away from 300. So, I'll let the internet decide. Thoughts?

I recently built a 300 to hunt with this fall. The nice thing about the 300 is if you don't like it, just sell the barrel and replace with 5.56. You won't know you don't like it until you try it.

Lol I'm in for the annihilation.

OP. Google 300 blk vs 5.54, should take you about 2 weeks to get through all the information.

Cliffs notes. 5.56 Shoots a bit flatter (most of the time) and 300 blk his a bit harder (most of the time).

Oh,  and a 300 blk suppressed sounds like a mosquito fart.

Joe makes a good point.  I'm planning on converting my 10.5 in pistol to an 8 in 300 blackout before too long.

I guess I never really thought about it like that. The simplicity of replacing an unwanted barrel is a beautiful thing. Thanks for the input.

5.56 is a more lethal round with greater range.  But subsonic 5.56 is anemic as hell.

.300 Blk can certainly get the job done, but suppressed is where it really shines; when you're limited to 1,100 FPS, its pretty obvious that a .30 cal 200-220 gr bullet > .22 cal 60-90 gr.

when the barrels get short its so ammo dependent for good performance, they can both suck with the wrong ammo and they can both rock

I have an I built two with 8" Ballistic Advantage barrels one 556 one 300. They both rock for their own unique reasons as your finding out.

Reloading the 300 makes it a lot nicer all around ....I have to tell ya the 556 is much more of a performer than I ever thought it would be, but again I am loading specific ammo for it as far as defensive type loads, I even load fmj plinkers hot for it

300 is a thumper, just plain fun to shoot and versatile not as harsh as the 556.....ammo is still its Achilles heal imo....not performance but price, availability and even for reloading it has a narrow group of usable powder compared to most cartridges it competes with .
go burn 500 556, who cares really? but a 500rd 300 blk day kinda hurts lol

If I could only have one I would take the 556 ironically, with a mountain of Barns 53gr TSX loaded over some H335

If you don't hunt, don't reload or don't shoot suppressed,  .300 Blackout gives you nothing over .556.

If all you're doing is shooting paper then save your money.

This and this




I had a 6.8 I used for whitetail.  In my opinion, unsuppressed, a better option than 300 for hunting. 95-110gr is plenty for 100-140# WV whitetail. I have better options than those calibers limited to ARs for hunting.  I plan to build an AR-10 in 243win, just about perfect for whitetail.  

In the end, nobody can tell you what YOU want.  

If you want to shoot suppressed, or use a short barrel, or shoot at close-range targets (<100 yards) 300BLK is definitely better. 5.56 is better if launched from a 16" or longer barrel at targets >200 yards or so. Between 100 and 200 yards, it's a toss-up.

Suppressed 300BLK is about as loud as a suppressed 22LR. The loudest noise is the bullet hitting the berm.

300BLK uses faster-burning powders, and it reaches max velocity in less barrel than 5.56. An 8" 300BLK has a lot more muzzle energy and a lot less muzzle flash, blast, and concussion than an 8" 5.56.

Given comparable energy levels, a .308 diameter bullet is going to put more of a hurt on a hostile target than a .224 diameter bullet. The disadvantage is that a larger-diameter bullet has more drag and will lose velocity faster than a smaller-diameter bullet. The larger bullet will also have more arc in the trajectory. So 300BLK is better at short range, and 5.56 is better at long range.