6.8spc

F

FairChase93

Active member
Alright guys do to an ordering error one of my gun buddies has all the parts for a 6.8 spc upper. I have the opportunity to purchase the parts cheap, but I really don't know much about the round. What are your experiences? Performance? Velocities and ballistics? What should I be able to expect from the cartridge?
 
I have a 6.8 SPC, and have killed deer and coyotes with it. I've never shot it past 300 yards, but it's a very good shooter up to that range. I mostly reload for mine, using 90 and 110 grain bullets and also shoot 110 VMax factory ammo. Like the above poster stated, you can find a lot of info over on the 6.8 forums.
 
Originally Posted By: FairChase93What are your experiences? Performance? Velocities and ballistics? What should I be able to expect from the cartridge?


REALLY like the cartridge in the AR-15 platform. Performance is good with 90-110 gr. bullets. For medium game, the 95 gr. Barnes TTSX is hard to beat. Shoots flat, and hits hard. For predators, I shoot either the Sierra or the Speer 90 gr. HP. Both shoot sub-MOA with the same case, primer, and powder charge, in my rifles. Not fur friendly, but effective. For SD ammo, I load 110 gr. VMax loads, and they also shoot well. Velocities out of my 1:11.25 ARP barrel run a bit over 2800 fps MV, with the 90-95 gr. bullets, with no signs of pressure on the case. Ballistics are pretty flat to 200 yds, with not too much compensation out to 300 yds. This round is probably what the AR-15/M-16 should have been chambered in originally.

Squeeze
 
Originally Posted By: SqueezeVelocities out of my 1:11.25 ARP barrel run a bit over 2800 fps MV, with the 90-95 gr. bullets, with no signs of pressure on the case.


What length barrel? I have a 16" barrel and with the 90 gr Sierra my chrony says about 2500 FPS using benchmark.
 
I've searched the topic quite a bit actually. There are always new and different opinions out there.

The barrel on this upper that I can get is 24 inches. I meant to include that in the original post and overlooked it. The majority of people I have spoke with have 16 or 18 inch barrels, curious if anybody else out there is running that long of a barrel with this round.
 
I too have an ARPerformance upper and really like it. It is a hammer for sure.

+1 on 68forums. That's your wiki.

What chamber does it have (needs to be gen 2)? Make sure it's not one of the old/bad ones (gen 1). Likely isn't a gen 1, but make sure. Agree that 24 inches makes absolutely no sense for the 6.8. A 24 inch 6.8 barrel is odd, which made me question the chambering. Also, what's the barrel twist? If it's not 11.25 or at least 11 I'd pass. YMMV.

And above all remember, cheap junk is still junk. You just have money left over to buy beer to cry into.

Sendit
 
I don't believe that I'd go 12 twist in 6.8, and I'm not going 24" either. I had a 16", just bought another 18" barrel. The gap to a 20" and a 24" just wasn't worth much.

Then again, I'm not building a 6.8 bench rifle. If I were building a bench rifle, it wouldn't be a 6.8. If you ARE, then good on ya. The 6.8SPC only has 10% more powder capacity than the 223rem, but almost 60% more bore volume (for the same length), so you don't get the same returns in terms of velocity per barrel length as you do in a 22cal. Data that I've found around from reliable sources show about 20fps per inch, so the difference in 18" and 24" is only about 120fps, but adds about a half a pound of muzzle weight, and 6" of extra barrel to snag on things.
 
Originally Posted By: reb8600Originally Posted By: SqueezeVelocities out of my 1:11.25 ARP barrel run a bit over 2800 fps MV, with the 90-95 gr. bullets, with no signs of pressure on the case.


What length barrel? I have a 16" barrel and with the 90 gr Sierra my chrony says about 2500 FPS using benchmark.

It is an 18" mid length gas port, if IIRC. ARP did a lot to research getting the most out of the 6.8 SPC case. The 1:11.25" 5R barrel, with a "DMR" chamber, is suppose to be the culmination of that work. And Benchmark wasn't the fastest powder. For the 95 gr. TTSX, I got something like 2820 fps ave, with Reloder 7, and with the Sierra 90 gr. HPs, Reloder 10x was like 2810 fps ave. I was a little surprised to see these velocities, too. My 18" 1:10" Wilson barrel isn't even close to these numbers(mid to upper 2600s IIRC). It does shoot these loads safely, but I do get the occasional ejector swipe marks on some cases.

Squeeze
 
My 6.8 AR consists of a 16" 11-1 twist Bison Armory mid length gas barrel with a SPC II chamber on a RRA upper receiver. I run a Colt FA Mil Surplus bolt carrier and a Stag 6.8 bolt. My lower is a RRA with a Timney trigger, and a 6 position Magpul MOE stock. I've been hand loading mostly 90 grain Sierra and Speer bullets for it since I've had it. I started out using H-335 powder in SSA cases, and was able to get them going from 2750 to 2775 FPS with no pressure signs, but my rifle was ejecting to 1 Oclock, and the load just felt hot. I was able to get just under one inch groups from these loads. I switched to RL7 a couple of years ago and have been able to get these same bullets up 2850 FPS. No pressure signs other than slightly flattened primers, but no more than factory loads from my .22-250. The rifle is ejecting at 3 Oclock, and isn't taking a beating. With a 200 yard zero, this load is dropping 10 inches at 300 yards. I haven't tested it any farther as this is about as far as I usually shoot. I've had this rifle for about 4 years now, and in that time have never had a malfunction of any kind with it. I've taken a good number of coyotes with it, and even put this upper on a pistol lower, loaded it with 110 grain Pro Hunters, and took a deer with it. It worked good on the deer too.
I think my 6.8 is just about the perfect coyote hunting AR for areas where I won't be getting shots much over 200 yards. For open fields though I still prefer my .22-250 or .243 Winchester bolt action rifles.
 
Thanks for all the opinions everyone. I've decided that this particular upper is not for me. Like a few others noted it seemed that the barrel length did not make sense for the caliber it is quite a heavy barrel to boot. The 6.8 may well be in my future but not set up like this.
 
The guy ordered parts for what was supposed to be a varmint rifle in 223, ended up getting barrel and bolt for 6.8. On a side note the barrel is an Anderson manufacturing, any one have an opinion on them for future reference?
 
Originally Posted By: FairChase93The guy ordered parts for what was supposed to be a varmint rifle in 223, ended up getting barrel and bolt for 6.8. On a side note the barrel is an Anderson manufacturing, any one have an opinion on them for future reference?


I have built a few lowers using Anderson lower receivers, and they seem to be okay.
 
Agreed - good move.

I might make the comment that this exact topic (how to squeeze more out of the 6.8spc?) is something that gets kicked around a lot, and frankly, that simple fact is what propagates the question, and gives the 6.8 a bad name (if you will).

When you look at the numbers, there's nothing "wrong" with the 6.8SPC except that it was born in the wrong century.

For everything that it is, the 6.8SPC is incredibly well designed, but it was released into a 21st century sporting culture that only looks at (and sparsely understands) two numbers, velocity and energy. ***Reminding here that kinetic energy depends most profoundly upon velocity*** And it gets compared most frequently to it's college frat brother, the 6.5 Grendel, and as such, the legend of the 1,000yrd 6.5Grendel AR propagates, and the 6.8spc gets dismissed as a 200yrd proposition...

So the 6.8SPC gets a reputation of being slow - making people assume that it needs to be hot-rodded to be useful - and a resulting reputation of being a short range solution.

And then you shoot them in the field, side by side. The 6.8 is a coyote HAMMER, with a very manageable trajectory. The relative drop of the 6.8 beside the 6.5 is almost negligible - if you can connect with the 6.5 at a given range, you can connect with the 6.8. The killing power for the two is almost identical over range as well.

I suppose we'll keep seeing these threads asking "tell me about the 6.8's performance," or "6.5 vs. 6.8," which are really just guys that are interested in the 6.8 that need convincing that it's not a mistake, or need convincing that the 6.8 will meet their needs, even if someone might try to denigrate them at the range for shooting it.

It's a great round for coyotes in the AR-15, with a longer effective anchoring range than the 223, and expansion velocities that make it surprisingly fur friendly. If you believe all of the anti-6.8 hype, then don't buy it. If you want to anchor coyotes as far as most AR-15 shooters can connect on one, then it's going to be a very promising round for you.
 


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