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Old June 8, 2014, 09:31 PM   #1
marine6680
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6.8spc barrel length

PSA has an upper right now with a 14.5" barrel and pinned flash hider, mid gas.

The only 6.8 they have longer is whole rifles.


I know the 6.8 was designed to be efficient in shorter barrels... But I was looking to scope it with a 3-9x or 12x round about. A pretty good bit of magnification.

Seems to me that a 16" to 18" would be better. I was originally thinking 18" as ideal.

What do you guys think.
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Old June 8, 2014, 10:53 PM   #2
thedudeabides
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I'd go with the 14.5 pinned.

6.8 likes short barrels.
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Old June 9, 2014, 12:32 AM   #3
jeager106
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What is the intended use for the 6.8?
If hunting then 20" would be best.
My Stag 6.8 is a 20".
If for defense then perhaps a shorter barrel but they why a hi
power magnification glass?
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Old June 9, 2014, 06:02 AM   #4
marine6680
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Will be shooting out to 2-300 yards... Not defense, just a range toy.
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Old June 9, 2014, 01:11 PM   #5
Derbel McDillet
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I re-barreled an older AR15A2 with a 20" 6.8 barrel so I could use it as a general purpose hunting rifle. I easily achieve 2600+ fps with 110gr bullets using H332, which is the same powder I use for .223/5.56. It's most accurate with the Sierra 110gr pro-Hunter JSP bullet. It also shoots very well with the Hornady 110gr BTHP with Cannelure.

Good luck!
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Old June 9, 2014, 03:25 PM   #6
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Hopefully PSA will get some different uppers in stock and on sale.
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Old June 9, 2014, 07:44 PM   #7
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My 16 inch Bison Armory is excellent
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Old June 9, 2014, 07:59 PM   #8
JD0x0
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Nothing wrong with more barrel length. Some people run barrels up to 24'' with the 6.8. And yeah, while the 6.8 was meant for shorter barrels, that doesn't mean it wont benefit from a longer one.

Quote:
8.5 in (220 mm) 2,450 ft/s (750 m/s) 1,199 ft·lb (1,626 J)
16 in (410 mm) 2,900 ft/s (880 m/s) 1,680 ft·lb (2,280 J)
24 in (610 mm) 3,050 ft/s (930 m/s) 1,858 ft·lb (2,519 J)
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Old June 9, 2014, 08:38 PM   #9
hodaka
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Based on your numbers, 100 fps for an extra 8 inches of length and weight is not much of a gain. My 16" shoots 5 shots into less than an inch at 100 at around 2600 fps. I had a Stag 20" for a while and it did not shoot any better, although a little faster. The 16 inch is fine.
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Old June 9, 2014, 11:08 PM   #10
marine6680
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So far I have found just the 14.5" at a reasonable price.

This is a low use toy mostly, so I was hoping to keep the overall cost down.

I have seen a few really nice uppers that I would like, but the cost is more than I am willing to pay.
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Old June 9, 2014, 11:33 PM   #11
tirod
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6.8 is a cartridge that isn't supported by the military contract system or taxpayer dollars. The barrels are largely made for the hunting and SD market, and the cut rate makers don't get orders for them much. They can keep making 5.56 barrels and not changing out the tooling means no profit loss.

As for barrel length, there are pros and cons. The 6.8 was built on the 14.5" military NFA barrel being the "correct" length and having 50% more power than 5.56 - out of that shorter barrel. What civilian shooters are stuck for are either pinned or 16" barrels to be legal - and that is where most of the market lies.

Does it do any good to go longer? First, there is no guarantee of an accuracy increase with a longer barrel. Second, the incremental difference of 100fps going to 18, or 200fps going to 20 can be easily achieved with handloads or Tactical ammo that requires the SPCII chamber. The reality is that a 6.8 with a barrel longer than 16" is just extra weight and length for basically nothing more than looks. The ballistics already overpower the 5.56, which was the whole point originally.

Nonetheless, on the internet, people have to play games and claim their's is better, and it helps if the barrel is longer and some reason given. Well, others have proven they can get over 3100 fps out of a 16" 6.8 with handloads, and nobody has documented or credibly claimed the extra 100/200 fps reliably kills anything deader, or shoots more accurately.

All this was cussed and discussed on boards for years before I built mine, and it's been assembled for three years already. Despite all the bickering and chest thumping, a longer barrel really doesn't do anything many claim - except look longer. If I need more fps, I shoot Silver State Tactical, and if that doesn't do it, then I'll get a handloader. But I frankly won't know what it would do without a chronograph to go with it.

Most 6.8 is SAMMI loaded at the original spec, playing with barrel length to boost it is just one way to gain some speed, and certainly has it's disadvantages. I rank 18/20" barrels right up with magazines that allow 2.30 OAL - it's usually a lot of work and money for a minimal improvement.
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Old June 10, 2014, 06:28 AM   #12
marine6680
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I wouldn't mind a 16 inch barrel. The pinned flash hider on a 14.5 is more trouble than anything.
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Old June 10, 2014, 07:01 AM   #13
bedlamite
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Using the same load, a longer barrel will gain about 20-30 fps per inch of barrel from about 12" to 24" in 6.8.

http://68forums.com/forums/showthrea...ch-Stag-barrel
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Old June 10, 2014, 01:17 PM   #14
JD0x0
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Quote:
Using the same load, a longer barrel will gain about 20-30 fps per inch of barrel from about 12" to 24" in 6.8.
To give a reference point, tests have shown that from 24'' to 20'' a 180 grain .30-06 will lose an average of 15fps per inch.
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Old June 10, 2014, 01:20 PM   #15
Unlicensed Dremel
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Go with 16" just in case you want to suppress it or something (rather than 14.5") - yet still maintain the very short & light feel.
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