SBR - 6.8 vs 5.56


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dusty9110
May 26, 2011, 05:48 AM
I have recently found myself yearning for my first SBR. I have been reading about the ballistic preformance of the 5.56 out of a short barrel and, from what I have gathered, the 5.56 round doesnt burn all of the powder when coming from a short barrel therefore not reaching high enough velocity to obtain peak performance upon contact with the target (I could be wrong about all of this so correct me if needed!). My question is this - Would it behoove me to pursue an SBR in 6.8? Will ballistics improve with this round coming from a 10.5 " barrel? How about a 7.5" barrel? I am ignorant about the 6.8 round so any input about accuracy out to 100 yards from SBR would be helpful also. Finally, if my wife finds out about the cost of this endeavor I will be the one of the only homeless men in America who owns an SBR. Thanks again for your help guys!

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LiquidTension
May 26, 2011, 06:26 AM
Just send in the paperwork and you'll be good. 6.8 and 5.56 use the same lower. The stamp is the major hurdle. Submit it now, research barrel lengths while you wait.

If your wife kicks you out over the $200 stamp you may want to invest in some sort of counseling instead of an NFA item.

MasterSergeantA
June 15, 2011, 05:57 PM
No short-barreled rifle will be more accurate than a corresponding rifle with a longer barrel (all other things being equal). And I do not have a bunch of statistics to support the argument. But in Iraq, we found that the 10.5" barrel on the 6.8 SPC guns gave us much better firepower than the 5.56 ones. I also liked the AK with the folding stock as a 'more-bang-for-the-buck' solution. Anything under 100m is easy for the 10.5" pretty much regardless of caliber. But the bigger bore carries more punch downrange. The 7.5" barrel is pretty much useless for anything but a PDW...and not a great idea even then.

JustinJ
June 16, 2011, 03:53 PM
5.56 is very much dependent on velocity. Any round will be more effective the faster it is moving upon impact but some much more so than others. 6.8 will be a better choice in an SBR from a wounding perspective however be aware that the ammo is much more expensive. A longer barrel is by no means more inherently accurate. However, the faster the bullet goes the flatter the trajectory and the less time for wind to affect it. In theory though a shorter barrel will be less prone to effects from harmonics.

SentinelStrategic
June 17, 2011, 02:05 AM
The question is what you are going to do with the rifle. If this is a range gun for recreation, training and leisure, it really doesn't matter. If it's for home defense, you're better off going with a pistol due to tight quarters.
If it's a duty rifle, then the difference is more applicable. The shorter the barrel you go, the bigger you want your bullet. With any rifle, going to shorter barrels will increase the amount of unspent powder and decrease the velocity of the round. Each round requires a different distance to achieve a full burn. This is why, with very short barrels, rounds like the 6.8SPC and .300AAC BLACKOUT are superior to the 5.56. However, the 5.56 is superior in accuracy and range when shot out of a long barrel.

I have a 7.5" PDW AR that I built in 5.56mm, and it's a blast to shoot. Blast is also an accurate term, because the concussion from the muzzle of that thing is tremendous due to the ignition of the unspent powder at the muzzle.
I also have and shoot other SBRs, and from what I've noticed, the shorter you go with a barrel, the lighter the bullet you want. This allows you to pull better velocity from the round. If you want a rifle that will be more predictable and capable in a shorter configuration in a duty/defense/offense employment, or in a hunting rifle configuration, get the 6.8SPC or .300AAC. If you want a rifle that's less expensive to shoot and is more for training and enjoyment, get the 5.56. Just be real with yourself and do an accurate assessment of what you expect out of the rifle, and realistically expect to do with the rifle.
I say this because lately, it seems that I've been getting contacted by a lot of clients (Non .le or .gov) that seem to honestly believe that they need a doomsday rifle in the next 48hrs, when in reality, the rifle will be shot at most once a month and sit in a case or gunlocker the rest of the time for the next 20 years. I mean, no offense to anyone, but some people have somehow got it into their heads that they're seriously going to either live out a real-life RedDawn scenario, or that zombies really do exist and are coming. There's a difference between having a gun for defense, and having a gun for some situation that would only occur in a Hollywood movie. Or Rio Linda, California.

I'm not saying this is anyone here. What I AM saying is to be realistic about what you will REALLY be using the rifle for.

9teenEleven
June 17, 2011, 10:36 AM
Two words: 300 Blackout

dusty9110
June 19, 2011, 12:09 AM
Guys I appreciate the insight and replies. I will be making my decision soon and the information is appreciated.

Nefarious79
July 27, 2011, 02:35 PM
300 AAC Blackout will outperform 6.8 out of a shorter barrel. Do you reload? Is cost or ammo availability a concern?

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