300 blackout vs. 6.8mm for SBR

[Amattern]

After I finish my current project its on to another SBR. I currently own a 16" Rock River AR. This time it is going to be a factory SBR. I'm down to three calibers, 300 Blackout, 6.8mm or just stay with .223/5.56. Which is a better choice? Anyone have first hand experience with either one? Eventually wanting a silencer any differences down the road when I decide to?

 

[Slow Hand]

Mine's not an SBR, but if you are wanting really quiet, go with the .300 suppressed. I'f you are wanting something much cheaper to shoot/not handload for, go with the .223. Once you've got the registered lower, it's easy enough to get another upper for it.

 

[lumpagus1]

From everything I've seen or read it seems like the 300 BLK has better ballistics then the 5.56 but you're wallet will be feeling the pressure with a change in caliber. As far as 6.8 SPC goes...I had high hopes for when the round first came out but it just doesn't seem like it's caught on nearly as well as I thought it would. I think the main selling point with the 300 BLK is the fact that you can easily convert a pre-existing 5.56 to a 300 BLK with a simple barrel change. I myself am contemplating building a 300 BLK. My one hindrance is the cost of the round, I don't do hand loads (at least not yet anyway) so I'm having to deal with factory/commercial ammo.

As far as a better choice goes...I think if I were you I'd avoid the 6.8 SPC (it's just not nearly as popular and it doesn't seem like there are too many manufacturer's who are building parts which revolve around the caliber...but that may just be my naivety). If you have a few 5.56 builds/firearms then I'd say give the 300 BLK a try, and if you don't like it...then swap it for a 5.56. Also when it comes to suppression, I'm hearing that the 300 BLK is ideally suited for a suppressor...not to say the other 2 aren't but all the informative pieces I've seen or read, praise the 300 BLK as a good round to suppress. Unfortunately I don't have any advice to offer as far as personal hands-on experience, sorry. Personally I'd suggest a 300 BLK.

 

[DownByTheTracks]

I would pass by the 6.8. My 300 Blackout was really awesome suppressed running subsonics. Was. I sold the upper because I didn't want to run supersonics suppressed, because, well it's not as cool. I could not justify $1 per round to train with.

5.56 11.5" with suppressor is what I'm running right now, and my wallet doesn't cry everytime I shoot it. I never shot them side by side, but my 5.56 seems about as quiet as a 300 BLK supersonic round.

 

[vitamink]

another vote for 300blk.

 

[jrainw]

300 Blk is perfect for short barrels. That said, I have a 10.5" 5.56 upper and a 10" Noveske 300 Blk. I shoot the 5.56 more, but the 300 Blk is incredible suppressed.

 

[MarioMarietta]

300BLK for sure! 6.8 is kind of a flop WAY EXPENSIVE and 300 BLK is soooo quiet!

 

[atalon]

Check on the video in this thread. Great details.

https://www.indianagunowners.com/forums/long_guns/245984-travis_haley_on_300_blk.html

 

[jmanrogers]

- 6.8 was a great idea but the military never adopted it for a reason
- .300 blackout is the latest and greatest and is definitely quite when shooting suppressed, however, ammo can be hard to find sometimes
- 2.23/5.56 is also quiet when shooting suppressed and ammo is plentiful

Here are the differences:

5.56x45 (.223 Rem)

• super sonic round
• Ballistics data
  • 55gr: Velocity = 3,240 ft/s Energy = 1,282 ft-lb
  • 62gr: Velocity = 3,100 ft/s Energy = 1,303 ft-lb
  • 69gr: Velocity = 2,950 ft/s Energy = 1,333 ft-lb
  • 77gr: Velocity = 2,750 ft/s Energy = 1,293 ft-lb

7.62x35 (.300 BLK)

• both super sonic and sub sonic rounds (sub sonic ideal for use with a suppressor)
• Ballistics data
  • 125gr: Velocity = 2,215 ft/s Energy = 1,360 ft-lb
  • 220gr: Velocity = 1,010 ft/s Energy = 498 ft-lb

Basically the 5.56 will give you more accuracy at greater distances than the .300 BLK however the .300 BLK will outperform the 5.56 in close quarters due to the heavier grain.
The energy between the 66gr .223 REM and the 125gr .300 BLK are marginally different but when you take in consideration that the bullet grain of the .300 BLK is much larger, this will inflict more damage at closer ranges.


Now, I am not knocking the 5.56 (.223) by any means...although this round is scrutinized by its small size, it remains an effective round as the military/NATO has used it since the 1960's.


It all boils down to variety since the AR-15 is already a modular rifle...if you have the money to have an AR for both rounds then go for it...what makes the .300 BLK so nice is that all you would need to do is purchase an upper with a .300 barrel; the BCG, Upper and magazine for the 5.56 will work hand in hand with this round.