Blast of 300 Blackout from 7-10.5 Inch Barrel

[DMW1116]

How does the blast of a subsonic 300 BO round compare to the blast of say a 9mm pistol (kinda bad) or a 14-16 inch 5.56 (really bad)? This is when fired unsupressed.

 

[Destructo6]

What muzzle device?

 

[DMW1116]

Standard birdcage for 300 BO and 5.56. None for 9mm.

 

[reddog81]

I've never noticed any obnoxious blast from my 10.5" 300 BLK with a Noveske Flaming Pig muzzle device. I'm not sure if that would be from the muzzle device being so amazingly effective or just the nature of subsonic 300 BLK. I wouldn't be surprised if the relatively small amounts of fast burning rifle powders used for the subsonic rounds are pretty much completely burned by the time they get to the muzzle. My only experiences with short barrel .223 ammo is out of a 10" contender and comparing that to the 300 BLK is a night and day difference.

 

[DMW1116]

The whole reason for the question is I am thinking of getting into an SBR. I shot a 223 pistol years ago and the noise and blast make them a sonic energy weapon for me, so I don’t want anything to to with that again.

9mm from a 6”-8” barrel would be an improvement over a regular 4” pistol barrel. However with 300 BO as an option I figured I’d better think about that too. With that I’d have the option to increase to supersonic rounds though “limited blast” shouldn’t be a thought at that point.

For a few reasons, 9mm seems the way to go but 300 BO may not be that bad in terms of blast as long as subsonic ammo is used.

 

[TitanicTortilini]

300aac achieves a full powder burn in an 8" barrel, so no concussion like a 223/556 or a 7.62x39 would produce. It might be louder than a 9mm, but not obnoxiously so. Put a blast can or a suppressor on it and it's surprisingly mild.

 

[DMW1116]

Right. This is a steppingstone type of notion. Either would be suppressible at a later date but would be pleasant enough to use without at least enough to get sighted in and familiar with them.

 

[DMW1116]

300aac achieves a full powder burn in an 8" barrel, so no concussion like a 223/556 or a 7.62x39 would produce. It might be louder than a 9mm, but not obnoxiously so. Put a blast can or a suppressor on it and it's surprisingly mild.

That doesn't sound too bad. The powder charges for a 300 BO are more than 9mm, but it also has a much bigger case, so I don't know how that would balance out in terms of blast. One big thing in favor of 9mm is the cost to shoot it. Putting an SBR together is probably within 10-15 percent for either one. Feeding them is certainly beyond that.

 

[reddog81]

9mm is certainly the logical answer is cost is a major factor and you aren't too concerned about ballistics. The weakest 300 BLK ammo trumps the most powerful 9mm ammo, but 9mm ammo can be had for under $.30 and 300 BLK ammo starts at $.70 and pushes close to $1 per round for subsonic (prices based upon a glance at SGammo's website).

 

[AK Hunter]

I hunt with my 8.5" barreled 300 blk pistol & don't use hearing protection so the blast is not that bad. In comparison I have a 7" barreled .223 that I have to use ear plugs & muffs but it's still too loud.

 

[DMW1116]

I hunt with my 8.5" barreled 300 blk pistol & don't use hearing protection so the blast is not that bad. In comparison I have a 7" barreled .223 that I have to use ear plugs & muffs but it's still too loud.

That was my experience with the shorter 223 as well. Even reloading 300 BO won't help much. Just a 208-grain projectile for subs is more than a whole 9mm round. I typically load 135-147 grain projectiles for 9mm, so they're a little more $$ than 115 range ammo but not much. Unfortunately, based on differences in velocity for 9mm rifle and pistol loads from Lyman, it doesn't look like 9mm benefits a whole lot from longer barrels. I was hoping for a jump like 357 Mag, but no such luck.

 

[tommy.duncan]

I have an 8" 300BO build with a flaming pig on it and it's not bad.
I built it as a pig gun initially. I plan on suppressing it, but haven't yet.
It has been a sweet shooter and not overly aggressive.
Hope you enjoy your shooter!!

 

[mavracer]

If you're building a 9mm it makes a pretty big difference if it's straight blowback or some kind of delayed like the roller delay Stribog or the CMMG radial delayed when suppressed.
With semi-auto port pop is usually between 130-140 dB.
I'll echo others my 8" 300 blackout has a Griffin linear muzzle device and my 10.5" has a Gemtech that's similar to a bird cage neither is terrible unsuppressed with just plugs. Compared to my 12.5" 5.55 with its 2 port brake that I've fired a total of 3 rounds unsuppressed because it's obnoxious even with double ear protection.