Can an Standard AR-15 with 5.56 upper be replaced with a 6.8mm upper easily

C

CowboyinIL

New member
Hello

Just curious if a Smith & Wesson M&P AR-15 with a 5.56 barrel (upper) have a 6.8mm barrel (upper) put on without changing anything else on the AR-15 rifle? If so, I don't believe that Smith & Wesson make an upper in the 6.8mm caliber, so could I use any brand upper like Rock River Arms or another well known brand? If that is a big yes, then anyone have any recommendations as to a good quality brand and a good twist rate (maybe 1:11). Third, is the 6.8mm pretty much like a .270 caliber?

Please let me know if anything else other than the actual barrel is needed to convert the caliber from 5.56 to 6.8mm.

Thanks to all of you guys in advance.


Cowboy

PS Will the 6.8mm vaporize a coyote or is it possibly fur friendly with lower grain v-max rounds?
 
Originally Posted By: CowboyinIL
Just curious if a Smith & Wesson M&P AR-15 with a 5.56 barrel (upper) have a 6.8mm barrel (upper) put on without changing anything else on the AR-15 rifle?

Yes

Originally Posted By: CowboyinIL
If so, I don't believe that Smith & Wesson make an upper in the 6.8mm caliber, so could I use any brand upper like Rock River Arms or another well known brand? If that is a big yes, then anyone have any recommendations as to a good quality brand and a good twist rate (maybe 1:11).

Stag, DPMS, Bushy, RRA... any quality upper you should be happy

Originally Posted By: CowboyinIL
Third, is the 6.8mm pretty much like a .270 caliber?

Please let me know if anything else other than the actual barrel is needed to convert the caliber from 5.56 to 6.8mm.

Yes the 6.8 is a .270" bullet but most common .270 rifle bullets are too heavy if you reload. Most 6.8 shooters use 110-115'ish weight rounds. Most 270 rifles use 130-150 grain bullets.

For the conversion:
You will also need a 6.8 magazine or a modified magazine to have reliable feeding with the 6.8 round.
There is a differrent bolt in addition to the magazine required if you are putting one together....not just a barrel swap.
 
So then I cannot just get the barrel / upper. I also need to get a bolt and a magazine? The magazine I get, but why the bolt? So, it will not work without getting a bolt also, correct?

Cowboy
 
Change the bolt head and barrel. Do make sure you get the sammi spec 2 1/11 4 groove barrel. I went with a complete upper from ben at bisonarmory.com That gives you the choice of using your .223 or the 6.8 upper.

For just a few dollars more than a off the rack upper, you can have custom upper made the way you want it from ben.

Which ever way you go, make sure you get the sammi spec 2. blue

P.S. i haven't touched any of my .223's since i got the 6.8spc.
 
You need the different bolt because the 6.8 brass has a larger diameter than the .223/5.56.

My 6.8 upper is a Rainier Arms Custom Elite, just to give you another option.
 
So you don't have to have one of the 6.8 lowers like they sell to make these work? I know Stag sells 6.8 specific lowers... I have a complete 5.56 Stag Lower Half, so all I have to do is get a complete upper like from Bison Armory and another Magazine?
 
Quote:so all I have to do is get a complete upper like from Bison Armory and another Magazine?

Correct. If you had a complete upper (with bolt/carrier group) and a magazine, you would be ready to go.
You could swap back and forth by pushing 2 pins, swapping uppers and changing mags.
The lowers are identical.
 
Originally Posted By: Evil_Lurker Quote:so all I have to do is get a complete upper like from Bison Armory and another Magazine?

Correct. If you had a complete upper (with bolt/carrier group) and a magazine, you would be ready to go.
You could swap back and forth by pushing 2 pins, swapping uppers and changing mags.
The lowers are identical.

Interesting... so why do they sell 6.8 specific lowers??
 
Cool, so what is the general cost of the 6.8mm spc with the complete upper bolt/carrier group in which you could just swap out the upper by "pushing the 2 pins"?

Cowboy
 
Olympic Arms sells one for $637 (catalog price) complete. Download their catalog here:

2009 catalog

Then look on page 24.

Quote:K8-MAG-UR These top end assemblies include a flat top upper receiver with picatinny rail, charging handle, bolt carrier
assembly, 24” or 20” bull diameter Ultramatch broach-cut barrel in stainless steel chambered to the Winchester Super Short
Magnum caliber specified. Also includes a free floating aluminum tube handguard with knurled surface and a gas block with
picatinny rail. Also includes one 7 round magazine for WSSM.
The WSSM upper receivers do
not have a brass deflector or
an ejection cover assembly.

K68-UR K68 top end assembly, 6.8 Remington / SPC $637.00



That's the SUM barrel that D-Tech uses, it should shoot bugholes.
 
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I bought a used Cardinal upper, popped the pins and put it right on the same superior lower I use on my 5.56 RRA upper. No problems.

That said some aftermarket triggers (or spring kits) will give you light strikes on the primers used by SSA in their ammo, but that's really not common.

What is important is the specifications of your upper. You want a 6.8 SPCII chamber and a 1x11 twist would be the best although the 1x10s work if you have the SPCII chamber. This will allow you to get the most out of your 6.8.

I'd give ben at bison a call and discuss your needs with him. I've heard good things about him and his prices are good. Also you could go to 6.8.com and get a lot of information from people who know a lot more about the round than I do.

You do need 6.8 mags. C products 25 round mags have worked good for me. PRI also makes mags and if you reload this will allow you to load the longest OAL of any of the mags and Barrett 30 round 6 8 magazines are the gold standard if you want the ultimate in relability.

As far as fur friendly, I'll let someone else answer that, I've yet to take a coyote with mine.
 
as you can tell i'm an RGuns fan!! noway associated with the site!!!! but man he has in stock deals and shipping is fantastic!!!! these come with the BCG and CH!!ooh and they have Sharps lowers for $55!!!

http://www.rguns.net/rifles/rifles-semiauto-ar15-uppers-68.shtml

DPMS 6.8mm 20" A3 Upper
With Bolt and Charging Handle
IN STOCK
$525.00 without carry handle
$625 with carry handle

DPMS 6.8mm 20" A2 Upper
With Bolt and Charging Handle
IN STOCK

DPMS 6.8mm 20" A3 QuadRail Upper
With Bolt and Charging Handle
IN STOCK
$630.00 without carry handle
$730.00 with carry handle

DPMS 6.8mm 16" M4 QuadRail Upper
With Bolt and Charging Handle
IN STOCK
$630.00 without carry handle
$730.00 with carry handle

DPMS 6.8mm 16" M4 Upper
With Bolt and Charging Handle
IN STOCK
$510.00 without carry handle
$599.00 with carry handle
 
I have a olympic .223 upper that I swap with a rra 6.8 all the time. Just remember to get the correct follower for your mags. I just keep a stack of .223 and 6.8 in the safe and grab rhe one I need when I swap uppers.
 


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