5.56 vs. 300 Blackout

[robert_smi2]

Ok, I am going to post this multi part question to see what everyone thinks and any suggestions you may have. I am building an AR Pistol and I have just about completed it and all I have to get is the barrel and gas tube. I was thinking about getting a 10.5" in 300 Blackout. My situation is I already have several in 5.56 and a lot of ammo for them so I would not need to purchase more ammo. But I really like the idea of being able to add a suppressor to go quiet.

So basically I am asking if the benefit of adding a suppressor is worth the extra cost in a more expensive ammo, and is there much of a difference in the ballistics of the two calibers.

If I do choose the 300 Blackout in 10.5" what would the best twist rate to use with a suppressor.

 

[nitrousfedlx]

300 blackout
Ballistic performance
Bullet weight/type Velocity Energy
125 gr (8 g) OTM 2,215 ft/s (675 m/s) 1,360 ft·lbf (1,840 J)
220 gr (14 g) OTM 1,010 ft/s (310 m/s) 498 ft·lbf (675 J)
78 gr (5 g) Lehigh Defense CQ 2,800 ft/s (850 m/s) 1,358 ft·lbf (1,841 J)
90 gr (6 g) Barnes OTFB 2,550 ft/s (780 m/s) 1,300 ft·lbf (1,800 J)

5.56 NATO
Ballistic performance
Bullet weight/type Velocity Energy
4 g (62 gr) SS109 FMJBT 940 m/s (3,100 ft/s) 1,767 J (1,303 ft·lbf)
4.1 g (63 gr) DM11 FMJBT 936 m/s (3,070 ft/s) 1,796 J (1,325 ft·lbf)
4.1 g (63 gr) GP 90 FMJBT 905 m/s (2,970 ft/s) 1,679 J (1,238 ft·lbf)

 

[nitrousfedlx]

So ballistics speaking, a good amount of difference. 300 blackout was designed for short barrels and suppressed while 5.56x45 was not. Mine and several other people's motto on here is suppress everything u can. Haha. Another specific is u can readily find 300 black subs, I'm not sure about 5.56/223. The pressure in that casing and speed of the projectile maybe too high to bring it down to subsonic levels?

 

[Dirty J]

5.56 subs are basically non-existent. And if you find some, they're unlikely to cycle an ar-15.

If you want to suppress something, 300blk is the way to go. It's a really fun round to shoot. Especially suppressed.

Just need to prep yourself for the $0.80-1.00/rd price of subsonic ammo to take full advantage.

 

[ReganR6]

Easy Answer!

If you plan on suppressing get the 300 Blackout!

If you never plan on suppressing get the 5.56!

 

[George P. Burdell]

You might consider a little bit shorter barrel if you go the 300 bo route. you will appreciate it if you put a suppressor on there. .556 isn't that great of a round out of a short barrel. You have to think about what you intend to do with it. Maybe considere a 9mm? Cheap subsonic Ammo and short barrel. The price of 300 bo Ammo is what keeps me away

 

[Dirty J]

300bo suppressed is recommended a 9.0-9.5" barrel. Extra length = extra velocity... which is what you don't want when running suppressed.

I use a 8.5" barrel on my 300bo

Easy Answer!

If you plan on suppressing get the 300 Blackout!

If you never plan on suppressing get the 5.56!

That is an easy answer... but it all depends on the proposed use.

Sub-sonic 300BO isn't great beyond 200m... huge hold overs... and suppressed 5.56 is still better than unsuppressed 5.56 - so get what suits your need.

If you have no specific need... and just want a cool new toy to shoot suppressed... than 300bo is the way to go.

 

[ReganR6]

300bo suppressed is recommended a 9.0-9.5" barrel. Extra length = extra velocity... which is what you don't want when running suppressed.

I use a 8.5" barrel on my 300bo





That is an easy answer... but it all depends on the proposed use.

Sub-sonic 300BO isn't great beyond 200m... huge hold overs... and suppressed 5.56 is still better than unsuppressed 5.56 - so get what suits your need.

If you have no specific need... and just want a cool new toy to shoot suppressed... than 300bo is the way to go.

That was my point. Without knowing what you plan on doing with the rifle was just my .02!

 

[ocean_glocker]

I'm running a 8" CMMG 1:7 twist barrel on my suppressed SBR and couldn't be happier, its the most fun gun I have to shoot. And I reload 245gr coated lead pills, and its brings the cost down alot.

 

[bensskateshop]

No matter the caliber or barrel length you decide on, Get the suppressor! Neither I nor my kids like to shoot un-suppressed anymore. The difference is truly amazing.

This year I hunted exclusively suppressed with both 5.56 and 300bo supersonic. I'll never go back if I can avoid it.