View Full Version : 6.8 vs 308
Im new to the ar world just got a stag and i love it,but i want more power than the 223 , the 6.8 looks like a good move up but it cost a bit more.the 308 aint to bad on price.I want to be able to put a big hog or mule deer down past 300 yards.What do yall think?
joetapout, go for the .308. It's a proven round.
joetapout, go for the .308. It's a proven round.
You need a whole new rifle to shoot .308. You just need a new barrel, bolt, magazine, and muzzle device (e.g. flash suppressor or brake) to shoot 6.8. The 6.8 rifle will weigh less and kick less than a .308 AR. There are excellent hunting rounds available for 6.8 that will take game up to 250 lbs (or more) at up to 300 yards. Oh, and 6.8 excels in barrels from 12.5 - 18", whereas .308 is just getting going in a 16" barrel and really wants 18" for good performance.
If you had a dedicated 5.56 upper with a .22LR conversion kit, as well as a dedicated 6.8 upper, you could plink, PLINK, and HUNT with the same lower, stock, trigger, etc.
It's not as easy to switch between 5.56 and .308.
I agree on the 6.8 upper, over a totally new, larger, heavier (approx. 10 lbs.) AR-10 .308 platform.
Remember, the 6.8 has similar trajectories to the 5.6 and the .308, and the kicker is, the 6.8 has 80% of the .308 power with mild recoil!
Wrong Forum,
These two rounds are not in the same class by any means.
shadowalker
11-25-08, 08:34
For hunting I'd go with the .308, if weight isn't a concern a LR-308 or AR10 would be fine, otherwise I'd look at a bolt action .308. You should be able to get a 700 SPS in .308 with a decent scope for ~ $680 so a little less than buying a 6.8 SPC upper and a scope.
The 6.8 SPC in an AR is limited to about 115 grain bullet weight which isn't awesome for hunting with. The 6.8 SPC has a little less energy than the .243 with comparable bullet weight. The 6.8 SPC does have better terminal ballistics than .223 but is not nearly as flexible as a .308. Use 110 grain .308 and you have slightly better performance than 6.8 SPC with the flexiblity of using 150, 168 or even 180 if needed.
I considered 6.8 SPC but with 75 grain .223 and 110 grain .308 I don't see a lot of benefit from a performance standpoint.
whereas .308 is just getting going in a 16" barrel and really wants 18" for good performance.
I was hoping for a 18" LR-308 but got a good deal on a 16". With 150 grain bullets I get 2650 FPS with ammunition estimated at 2800 FPS. I've found .308 loses 20-25 fps per inch of barrel. Muzzle flash / recoil is very controllable and blast is not bad at all, I get ~ .7 inch groups at 100 yards. It is a little heavy at ~ 10 lb with a bipod but not too bad.
Magazine cost is about the same, a little cheaper for the LR-308 compared to Barrett 6.8 mags.
.308 has far more ammunition choices both assembled and in component form.
Remember, the 6.8 has similar trajectories to the 5.6 and the .308, and the kicker is, the 6.8 has 80% of the .308 power with mild recoil!
It has 80% of the energy of a 110 grain .308 load which is also pretty low recoil. The 6.8 SPC is probably quite a bit lighter than a LR-308 too. With a 8 pound 6.8 SPC free recoil is about 6.4 ft/lb with a 9.5 pound LR-308 it is 7.8 ft/lb so pretty comparable.
6.8 SPC with 110 grain bullet at 2600 fps has 1650 ft/lb of energy and momentum of 40.
Even with a 16" barrel a .308 should get around 2965 FPS with a 110 grain meaning 2147 ft/lb of energy and a momentum of 46.
With a 150 grain bullet at 2650 fps you get 2338 ft/lb of energy and momentum of 56 and it'll stay super sonic past 800 yards.
6.8 SPC 110 grain at 2600 FPS
http://ang.idahoimageworks.com/jas/68110.png
308 110 grain at 2965 FPS (16" barrel)
http://ang.idahoimageworks.com/jas/308110.png
More energy in the first 400 yards
308 150 grain at 2650 FPS (16" barrel)
http://ang.idahoimageworks.com/jas/308150.png
At 400 yards 56% and at 600 65% more energy than 6.8 SPC
308 150 grain at 2800 FPS (22-24" barrel)
http://ang.idahoimageworks.com/jas/30815024inch.png
I believe you are comparing the 6.8 based on the old 1:10 twist barrel limitations. The new industry standard is now becoming 1:11 twist, which opens up far more performance for the 6.8mm. Stag is just one of the first factory AR mfg. introducing the 1:11 twist for lower pressure and higher performance. Many more to come. Stay tuned for major changes in the 6.8mm come January 09. It's not a replacement for .308 lovers, just better performance in a standard AR platform for a mid-range (300 yd.) cartridge.
shadowalker
11-25-08, 16:45
The bullet weight limit isn't due to barrel twist, it is the cartridge overall length limit imposed by the lower receiver and magazine. The 6.8 SPC fires the same diameter bullet as the 270 but with far less powder.
A 1:11 twist should favor lighter, not heavier bullets. Heavier bullets have more momentum so tend to penetrate better, they are more heavily constructed, hold onto velocity longer and aren't as affected by wind. For better performance from a .277 diameter bullet I'd look at the 270.
In 6.8 SPC Hodgdon's max load for a 110 grain bullet using H4895 is 29 grains and is a compressed load at 42,400 PSI, plenty of pressure headroom but no more space for the powder. The .308 max load for a 110 grain bullet is 49 grains and is also compressed but with an extra 20 grains of powder.
I'm not attacking the 6.8 SPC, but I think it is a solution to a problem that was already solved quite nicely by 110 grain .308 for a lot of people. 6.8 SPC does allow a person to carry a little more ammo for the same weight.
The 6.8 SPC is better compared to 7.62x39 than it is to 7.62x51.
Get the latest info at www.68forums.com
The bullet weight limit isn't due to barrel twist, it is the cartridge overall length limit imposed by the lower receiver and magazine. The 6.8 SPC fires the same diameter bullet as the 270 but with far less powder.
A 1:11 twist should favor lighter, not heavier bullets. Heavier bullets have more momentum so tend to penetrate better, they are more heavily constructed, hold onto velocity longer and aren't as affected by wind. For better performance from a .277 diameter bullet I'd look at the 270.
In 6.8 SPC Hodgdon's max load for a 110 grain bullet using H4895 is 29 grains and is a compressed load at 42,400 PSI, plenty of pressure headroom but no more space for the powder. The .308 max load for a 110 grain bullet is 49 grains and is also compressed but with an extra 20 grains of powder.
I'm not attacking the 6.8 SPC, but I think it is a solution to a problem that was already solved quite nicely by 110 grain .308 for a lot of people. 6.8 SPC does allow a person to carry a little more ammo for the same weight.
The 6.8 SPC is better compared to 7.62x39 than it is to 7.62x51.
No one is saying 6.8SPC is a replacement for .308. But if you already have an AR-15 type rifle and don't want to purchase a completely new rifle, a 6.8SPC upper will let you hunt feral pigs, mulies, etc, humanely and effectively out to 300 yards (or farther, if you have the shot and know how to take it). It beats the pants off of any 5.56 loading. For example, if you have a 16" 6.8 barrel with an SPCII or DMR chamber (analogous to 5.56 and Wylde chambers), you can drive a 110gr Accubond at 2700fps. And that's SSA factory ammo, not some crazy handloader's bleeding edge creation. No, not .308, but astonishingly good nonetheless.
shadowalker
11-25-08, 18:07
If you want a dual purpose defense / light hunting rifle 6.8 can be a good choice, if you primarily want it for hunting you can do better.
110 grain is marginal on larger deer, the 243 has higher sectional density and higher velocity and is still marginal. Yes it CAN, even probably will work especially at shorter ranges but larger calibers give more range, tolerance for shot placement and makes it more likely to make a humane kill. Also the OP asked about ranges over 300 yards which is where larger calibers would be a bit better.
If you don't already have a rifle, a LR-308 or AR10 is about the same price (~1K for LR-308, Stag suggests $1045 for their 6.8 SPC). With the LR-308 and AR10 being more adaptable due to far more ammunition choices. You can also get a LR-308 in .243, .260 and a few others.
A SPS 700 or Mossberg ATR or Stevens rifle with scope will come in right about the same price if not less than a 6.8 upper and be in a much more capable hunting caliber.
Dr. Quickdraw Mcgraw
11-25-08, 18:13
Perhaps a 6.5 grendel would be a better choice for you.
shadowalker,
Your comments re. 6.8 mm terminal performance are not entirely accurate.
Part of the USG testing of 6.8 mm involved controlled harvesting of deer by Federal Game Wardens--they were quite astonished by 6.8 mm capabilities on deer--it is anything but "marginal" on deer, even larger ones...
For those with Gun & Shooting memberships (Chuck Hawks' site) there is an interesting series of reviews. One on the 6.5 Grendel, another on the 6.8 SPC, and a third comparing the two. Basically they rate the two as quite acceptable deer cartridges out to 250yds. They also saw quite a bit of handloading potential in the 6.8 SPC. If you don't have a membership and are interested in an unbiased opinion it might be worth $5 for a one month membership. But then again DocGKR has spoken and I listen very-very closely to anything he has to say.
Edit: One key myth-busting point that they made was that they found that the only advantage to the 6.5 Grendel over the 6.8 SPC was the slippery shape of the match style bullet used in 6.5 Grendel factory loadings. They felt that given the same bullet shape that the 6.8 with its slightly higher muzzle velocity could easily match the long range performance of the Grendel. And that the 6.8 had more room for improvement in the hands of handloaders.
Perhaps a 6.5 grendel would be a better choice for you.
Probably the best "all around" round out there. Just not many ammo choices.
I am on Constructor's list for a new 6.8 Xtreme. I primarily hunt with a bow, but may use the 6.8 on occasion. I traded my 308 since it was too heavy for what it offers, in my humble opinion.
Here is something I wrote on another forum:
_______________________________________________________________
I had a 16" AP4 with quad rails. I mounted a Kahles 2-7x Multizero with a Laure SPR and it weighed 10 lbs.
Pluses-
Very accurate with cheap soft-point ammo. I shot 5/8", 3-shot groups at 200 yards off a bench. 100% reliable with the ammo I used (Federal Hi-shok, about the cheapest non-surplus you could find at the time (Wal-mart)). This carbine was fun for blasting at 100-200 yards and even plinking at 400-500 yards (scope had 5 zeros for quick elevation adjustment).
Minuses-
HEAVY! The carbine was "ok" with irons, but with the Larue mount and 2-7x if felt slow and heavy at 10lbs especially compared to an AR15. My hunting rifle (bolt action) was 8lbs with 4-12x scope for comparison and it was a 300 WSM (much more range and energy, but was a bolt action and follow-up shots wouldn't be as fast). The AP4 is very heavy under the handguards and this probably helps with accuracy, but also makes the rifle very heavy.
The other downside is that the short barrel wastes some powder so a 16" barrel on a 308 duplicates a 300 Savage ballistically. Don't get me wrong here, this smokes a 5.56 but a 10lb AR that duplicates a 300 Savage is not my idea of being combat or hunting "efficient". The 300 Savage is a great deer hunting cartridge, but its a little weak for a 10lb platform, in my opinion.
You could get a longer barrel version of the LR308, but then they get even heavier. If you want a bench rifle, that would be fine but its not realistic for hunting on foot unless you like carrying extra weight.
I'm not a big fan of the .308 for longrange either so the 24" LR308 rifles or the 24" AR10 rifles are not appealing to me. I would choose a bolt action in a different cartridge for a longrange rig but that is my preference. Many people like the 308 (semi and bolt) for longrange, and some people like the AR10/LR308 for medium range shooting with fast follow-up shots. It really depends on what you intend to do with this rifle.
I worry about FINDING 6.8 spc ammo if it never "catches on" with the USARMY -- 308 is everywhere. Right now 6.8 is way more expensive than 5.56...
Yall guys have been great thanks for all the info.I think I will stray away from the ar platform and go with a remmington bolt action in 243.
The 6.8 SPC is better compared to 7.62x39 than it is to 7.62x51.
I am intrigued. I am recent to AR's having been a Com block fan for a bunch of years. Will a 7.62x39 upper work on a .223 lower? I find myself eyeballing other caliber uppers as the idea of ammo restrictions and new presidents loom in the nearer future. Any safe bets? I haven't looked at balistics charts yet, but then I just got up in the middle of the night for an OJ and happened into this thread. What does the 6.8 SPC and 6.5 Grendal offer that the 7.62x39 doesn't?
Yall guys have been great thanks for all the info.I think I will stray away from the ar platform and go with a remmington bolt action in 243.
My longrange paper puncher will be a heavy barrel 243. I'll have to wait to build it after my AR collection is finished. If you plan to shoot long/heavy bullets just make sure you get the proper twist. Most hunting rifles should be able to shoot the 105 AMAX off the rack. Run the ballistics of this bullet at 3000 fps. Its impressive and not even the best bullet for the 243. Have fun.
constructor
11-27-08, 12:03
SSAs factory loads for the 6.8 are pushing 115gr bullets 2690-2700 fps from a 16" barrel now. He tells me he wants to develop a real +p load for barrels with the correct twist and chamber lke the DMR chamber and 11-12 twist. I pointed him toward the Swiss powders like RE17(not using RE17 just powders made with the same process) to get more velocity out of the same charge.
The 85gr TSX loads he has now are 3000fps.
With hand loads I can get 2950fps from a 110 Accubond or 110 Barnes TSX out of a 20" barrel, and 3200 with the 85 TSX.
The max distance at my range is 464 yds. I set my 308 and my 6.8 for 300 yds zeros, at 464yds the 6.8 needs less come up with 110gr hunting bullets than my 308 does with 155gr Lapua match bullets.
Terminal results on animals is great, we shot several hogs in Texas a few months ago then decided to shoot one large hog apx 275lbs through the thickest part of the shoulder with the 110 TSX and a 80gr GS custom bullet. We set the hog at 100 yds and shot the TSX at 2900fps through both shoulders it destroyed both shoulders and exited, The little 80gr GS custom did the same.
The 110 Sierra Prohunter would be better for deer but killed several hogs that weekend, The prohunter went through the first shoulder but hit the inside of the far shoulder busting it but it did not exit.
On a deer or hog a Prohunter would work well in a heart lung shot, If you like to blow their shoulders where they don't run A Barnes TSX or TTSX will work better.
Two years ago I dropped a mule deer at 428yds with a 110gr Prohunter, this year I shot an elk at 372yds with a 110 Accubond. I was hunting deer again but had an elk tag so I took the shot when the elk stepped forward with his left front exposing the heart area. I am not recommending the 6.8 as an elk rifle but it can be done if you wait for that perfect shot.
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