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View Full Version : 6.8 SPC or 5.56 20" A2 Upper


Uranium238
04-17-2012, 8:43 AM
I stumbled across an article recently that the purpose of the 6.8 SPC cartridge was to increase the stopping power on M4s in the battlefield. This has made wonder about the use on a 20" rifle. My next build I am looking for a classic AR15 A2 look, but am stuck deciding between a 6.8 or 5.56 caliber. I assume that a 20" will carry more energy for the 6.8 cartridge, but not the speed of a 5.56. Of course, this depends on the grain of bullet as well. I am open to hear recommendations or suggestions on what upper to use for my next AR build. :cool:

HK Dave
04-17-2012, 8:58 AM
What is the intended purpose of the rifle?

Standard
04-17-2012, 9:15 AM
20" 5.56

swl
04-17-2012, 9:34 AM
Are you a reloader? If not, 5.56. Heck, even if you ARE are reloader I'd still say 5.56. Price out 6.8 spc and 5.56 ammo and see what I mean.

Unless you're just building this rifle as a "once in awhile" shooter you'll spend a fortune on ammo. If you're building it for hunting, well then you should probably just go with an AR-10 build, because even with the increase in costs for AR-10 parts you'll still come out ahead by the time you've put a couple thousand rounds through it. It really depends on what you intend to use the rifle for.

xpbprox
04-17-2012, 9:36 AM
Why not a 6.5, wolf makes ammo for it. But if you plan on shotting this thing a lot then you might better off with a 5.56...

Uranium238
04-17-2012, 9:44 AM
It won't be shot off a lot. I have seen some pretty good prices for ammunition online. I don't mind spending $1 per round, but I don't expect to be shooting it off every week like I do with the CAR-15 I built.

chicoredneck
04-17-2012, 9:49 AM
The 6.8 was designed to be used in carbine length barrels. You will not see much velocity gain going from a 16" to a 20" barrel in 6.8.

Mamluke
04-17-2012, 11:55 AM
The 6.8 was designed to be used in carbine length barrels. You will not see much velocity gain going from a 16" to a 20" barrel in 6.8.

^^^ This

Go 5.56 out of a 20" barrel, 70 grain tsx. Nice & flat Ballistic Arc.

.........

mif_slim
04-17-2012, 11:57 AM
Yup, either 5.56 or 6.5 for 20".

warkaj
04-17-2012, 12:01 PM
Well look at this possibility... if everything goes to complete hell what kind of ammo do you think is going to be laying around plentiful? .223/5.56 or the 6.8?

I'd put my betting cash on 7.62x39 / 7.62x51 / .223, 5.56 being the plentiful rounds laying around to resupply on.

Same goes for pistols... 9mm, .40, .45... the .44 and .357.. more exotic some say. the 5.7 very exotic.

I go for the easily replenished ammo myself. Just my .02's

clutchy
04-17-2012, 8:46 PM
The 6.8 was designed to be used in carbine length barrels. You will not see much velocity gain going from a 16" to a 20" barrel in 6.8.

this^ you're trying to hamfist a cartridge into a purpose it wasn't meant to be used for.

6.5 loves long barrels!

5.56 was designed for a 20" barrel out of the AR platform!


6.8spc is an awesome cartridge b/c it does pretty much anything it can do out of a a 16" barrel.