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Such a dilemma...

H60Gunner

Registered User
Contributor
According to what I've read, and I am no expert, the 6.8mm is ballisticly superior to the 5.56mm in the short barrel A4 config.
But if you shoot alot, maybe the 5.56 is a better fit due to the cost of ammo.
 

Rocketman

Rockets Up
Contributor
I own both and love the 6.8 SPC. IMHO it makes an AR the weapon it should have been to start with. You can get factory ammo from SSA that will push a 90gr bullet 3000 fps out of a 16" barrel. That's smokin for a short barrel. The 6.8 SPC is a fantastic deer round. People are killing a lot of tough feral hogs with it too. If I every have to do a damn damn on any nasty zombies around the house I hope I have a 6.8 SPC in my hands.

That said if I only planned to buy one AR it wouldn't be a 6.8. Like you said ammo costs are pretty high and it's important to shoot a lot if you plan on being any good at it.

My advice is to buy an AR in 5.56 first and later an upper in 6.8. Pick up a couple of 6.8 SPC mags and you are good to go.
 

JSF_Dreamer

Busted Head
I'm a total noob at the AR scene. A 6.8 upper will fit on a 5.56 lower?

I love target shooting so I will probably go with the 5.56 since the ammo is so much cheaper.

Either way, I'll be happy to own either. If anyone knows anyone selling an AR in P-cola in good shape and a good price, let me know.
 

Rocketman

Rockets Up
Contributor
I'm a total noob at the AR scene. A 6.8 upper will fit on a 5.56 lower?

Yes it absolutely will. Anybody's 6.8 upper will fit on anybody's 5.56 lower. If you buy a complete 6.8 upper (which includes the bolt and bolt carrier) All you need to add is a 6.8 mag.

6.8's use a different barrel, bolt and mag. Everything else is interchangeable including the bolt carrier.
 

Fog

Old RIOs never die: They just can't fast-erect
None
Contributor
Is the 6.8mm Rem SPC the same as the [relatively] new Rem. 260 ??
 

Rocketman

Rockets Up
Contributor
Is the 6.8mm Rem SPC the same as the [relatively] new Rem. 260 ??

No it's not the same round. The 6.8 uses a .270 cal bullet and was derived from the .30 Rem case.

I don't know much about it but I just read that the .260 Rem uses a .308 case necked down to a .264 cal bullet. It looks like it may shoot the same 6.5 rounds that the 6.5 Grendel uses. If so that would make it a somewhat better long range round than the 6.8 SPC. But I think it would also mean that because of the longer case it wouldn't fit in a standard size AR lower just like a .308 won't.
 

Bevo16

Registered User
pilot
You can't go wrong with Rock River. What is 6.8 ammo go for?

AFTER I got my RRA AR in 5.56, I was looking for a more robust round and went with the M1A over the LAR-8 from RRA. To my surprise (and with some help from Rocketman), I have found .308 ammo that is basically the same price per round as 5.56.

If you are just going to punch holes in paper, get the one that you can do it cheaper. If you are going to use it for something other that that...get the one that fires the round that performs the way you want it to.
 

Rocketman

Rockets Up
Contributor
You can't go wrong with Rock River. What is 6.8 ammo go for?

Unfortunately 6.8 is very pricy. More pricy that both 5.56 and .308. Part of the problem is that no one is yet making a relatively inexpensive "plinking" round. There are several manufactures who have said they will but demand for components is still outstripping supply by far. There is no surplus in 6.8 SPC either which doesn't help.

Hands down the best you can buy is made by Silver State Armory (SSA). http://www.ssarmory.com/6.8ammunitionsales.aspx

Right now their least expensive round is the 115 gr Sierra OTM at just under $20.00 for a box of 20. Their least expensive round ain't cheap for sure but it is also the most accurate factory round I've ever shot out of an AR. It produces a seriously bad ass wound profile out of a 16" barrel as well.

Their "plinking" round is supposed to be out at the end of this month and priced at about $13.00 a box.

If you have a 6.8 and plan to shoot a lot you have to reload right now. Or you can do what I do and shoot the hell out of my 5.56 and save the 6.8 for killing hogs and zombies.
 

H60Gunner

Registered User
Contributor
They make dies for the 6.8mm. That may be a little cheaper if you handload.

I would do exactly what Rocketman said and start with a 5.56 then just buy a 6.8 upper later.

Personally, if any of my AR lowers ever arrive I think I will build one in 6.8mm.
 

XeroJaeger

New Member
You can't go wrong with Rock River. What is 6.8 ammo

I respectfully beg to differ. In the m4 pattern rifle series (for civvie and LEO use), RRA is around the moderate level in terms of QC.

Check out http://spreadsheets.google.com/ccc?key=pwswheghNQsEuEhjFwPrgTA

Some good info on configurations of the rifle. A lot of the same manf's have uppers and BCGs in 6.8. Its a powerful cartridge for military use. However, civilian-side, it depends on what you want the rifle for. If you want a battle rifle for home defense or whatnot, there are superior alternatives for FAR cheaper (esp. in the realm of ammo cost). If you want it for a hunting rifle, I recommend upgrading to the AR-10 frame and just going .308. More punch, same tacticoolness.

-X.
http://spreadsheets.google.com/ccc?key=pwswheghNQsEuEhjFwPrgTA
 

Rocketman

Rockets Up
Contributor
I respectfully beg to differ. In the m4 pattern rifle series (for civvie and LEO use), RRA is around the moderate level in terms of QC.

If you feel you have to have all mil spec and don't mind paying the premium, that chart really has developed into a great tool over the years.

I was issued Colt A2s by the Marine Corps and they served me well. That said in the last 30 years I've owned Colts, Bushmasters and Rock River ARs and put 10's of thousands of rounds down range. Several times over 600 mostly rapid fire rounds at a time. I have yet to have a Rock River or Bushmaster fly apart because it doesn't have a shot peened bolt. I've owned a couple of RRAs that would shoot rings around my Colts in the accuracy dept too. As you say, it's a matter of choice because they all seem to work well.

By the way, I wonder why that chart doesn't show Colt second to Noveske? After all Colt doesn't show a lifetime warrenty and Noveske does.........I'm just sayin
 

H60Gunner

Registered User
Contributor
How many calibers?

Searching around, I found some interesting calibers that can be used on an AR lower.

AR-15, without bolt modification
.17 Remington
.20 Tactical
.204 Ruger
.221 Fireball
.222 Remington
.222 Remington Magnum
.223 Remington (5.56x45mm)
.223 Remington Ackley Improved
6x45mm
6mm Whisper
6.5mm Whisper
7mm Whisper
7mm TCU
.300 Whisper (.300/221, .300 Fireball)
.338 Whisper

AR-15, with bolt modification
223 WSSM
5.45x39mm (.21 Genghis)
243 WSSM
6mm PPC
6mm BR Remington
6.5mm PPC
6.5mm Grendel
25 WSSM
6.8x43mm SPC
.30 Herrett Rimless Tactical (6.8x43mm case trimmed to 41mm and necked up to .308; the 6.8mm version of the .300 Whisper)
7.62x39mm
.357 Auto
.458 SOCOM
.50 Action Express
.50 Beowulf

AR-15 using a simple blowback operation
.17 HMR
.22 LR
.22 WMR
9x19mm
40S&W
10mm Auto
45ACP

450 Bushmaster- Didn't say if this caliber required a bolt mod or not.
The forum I plagiarized this from went on to list a whole bunch of others, some one of a kind rifles, including the .50BMG. I am talking about calibers which will fit into the magazine well of a mil spec AR lower.

I have no idea what the bolt modification is, can someone explain?

I understand the blowback system ie. no gas tube, and assume it is built into the upper for the required caliber.
 

Rocketman

Rockets Up
Contributor
I have no idea what the bolt modification is, can someone explain?

I understand the blowback system ie. no gas tube, and assume it is built into the upper for the required caliber.

I can speak to the bolt mod for at least some of the calibers you mention (6.8 SPC and 7.62x39 for sure and probably many of the others that are based on smaller diameter cases)

The only bolt mod necessary for these two is that the bolt face is "reamed" out to accept the larger case diameter. I'm certain nothing else need be changed on the bolt itself unless maybe someone might put in a different extractor spring. I don't know why they would though.

I have read where some early 7.62x39 bolts had problems breaking because they lost some strength when reamed to accept the larger diameter. I don't think this was a huge problem but it did happen early. I haven't heard of the 6.8 having this issue.

Don't know about the blowback ARs
 
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