Long barreled 6.8mm AR project

[Float Pilot]

This is a stainless 24 inch Black-Hole weaponry poly rifled barrel. 1 in 11 twist. replacing the 16 inch Stag bbl.
Originally I was thinking of just using a standard A2 hand-guard set and a fold-up sight type gas block. But this baby is so long it may need something else. Maybe a lighter weight free float tube fore-end. The barrel has a standard diameter area by the gas block.

Any of you AR freaks have opinions for keeping the weight down? This is just going to be a field gun and not a bench rifle. I am using a regular A2 buttstock

 

[MrCleanOK]

If you're really trying to keep the weight down, I suggest the following:

1. Lo-pro gas block, and just use an optic.
2. Rifle length carbon FF tube
3. Chop 4-6" off the end of the barrel

 

[Tirod]

Long barrel 6.8's exist, but it was specifically designed by SF/AMU to be optimal at 14.5" as an improved cartridge for tactical combat shooters. With a 16" civilian barrel, it's already longer.

Existing tests with chronographs show the longer barrels don't add as many feet per second with increased length like other calibers, another indication the cartridge is designed for short barreled use.

What's also interesting is that most of the ammo loaded is done to SAMMI specs, which aren't taking advantage of the improved chamber and rifling of the SPCII configuration. Improved velocity and power are a box of Tactical Loads away, and you don't have to tote the extra 8" of dead weight. There's no guarantee barrel length creates accuracy unless the FSB is extended way out there - and if an optic is used, that will be the limiter.

Since a free float can't improve the barrels inherent accuracy, because it can only protect it against outside influences, the additional cost is almost unnecessary on a field gun. The added weight of the Rifle+ rails is heavier than issue handguards.

Cost? Adding up all the potential expense and compare that to how much a simple reloading set would run - under $150. And it will deliver better loads that match the gun and discover it's maximum allowable velocity - which is cheaper and likely higher than what the barrel length addition delivers with standard SAMMI loads.

Just some of the thoughts behind the simple response, "cut the barrel down." It's not a reflexive knee jerk opinion, it's based on what this cartridge is all about.

 

[Zerodefect]

Trying to save weight on a 24"???? Don't bother, you'd only end up with a unbalenced hard to shoot AR. AR's don't get too heavy anyways.

I'd use a Daniel Defense 14" lite rail with Magpul XTM covers, low pro gas block, and a Magpul PRS stock. Then get a bipod with a QR from Larue.

 

[Float Pilot]

compare that to how much a simple reloading set would run -

I guess you do not know me. I have a small building dedicated to hand-loading, with 3 presses. Over the past three years or so I have exhausted most possibilities with various loads in the factory 16 inch barrel. The data is published in a few places.
I was going to sell the rifle since it had become boring and I had moved on the other projects. But it did not sell.

So like all shooters and/or aircraft owners, I did what always happens....
If you can't sell it, throw more money at it ,,,until it becomes interesting again.

So I am starting off long and will work my way shorter as I experiment with more loads. I keeps me from going hermitile during the long winters.

I was looking for brand name comparisons for parts and vendors. Most of my experience with the AR system is military.

 

[Blue Armadillo]

Not a bad topic for my first post...
I've read and heard all the conventional wisdom regarding the 24" 6.8, and would still love to have one.
And it's because I just like long-barrelled rifles.
It's my $$, and my problem if it's heavy, so who cares?

 

[Float Pilot]

Clark, DPMS, and Precision Reflex make carbon fiber hand guards that are pretty light.
I'd like to see a weight comparison someplace...
The PRI is much more than the DPMS or the Clark.

The instructions for the DPMS and the Clark call for using glue to affix the tube to the barrel nut...
I can see there might be some downside to the carbon fiber that I do not know about yet.

Somebody used to make a slightly longer than normal handguard. That might make this long barrel actually appear more balanced.