[mrpopgun]

So, I'm looking at the 6.8's and 6.5's right now for my next upper. Coming into this, I thought I was a surefire 6.5 buyer. The info on this site, though, is definitely making me step back and really examine the two cartridges.

Demand: MOA to 600yds
Want: 1/2 MOA to 600yds

After looking back and forth, comparing ballistics, throat erosion and what not, I'm still left with a fundamental question: How do these two rounds compare on a 600yd MOA basis. Actually, the question is a quite a bit more general than that: Any rifle I buy I want to be as accurate as possible. Stripping out ammunition, shooter and environmental factors, how do I evaluate one to be any more inherently/mechanically accurate than another without either a guarantee by the manufacturer (that can be acted on) or real world tests?

Truth is I am looking for a < 300yd deer rifle that will serve secondary duty as a varmint and target rifle. No issues with the first, pick the upper of your choice and you're taken care of. The issue lies, however, in that I am also an accuracy nut and like to shoot out as far as I can for varmints and paper. At that point, you can impress me all you want with ballistics, but if the round is hitting at lightning fasts speeds but turning in 3-4 MOA groups, I just don't care. The chart here makes me think of just how disappointed I would be in all but the MSTN and Noveske rifles on that chart

So, what goes into building a sub-MOA AR in 6.8 (or any other caliber for that matter)? What should I be looking for specifically to ensure the highest accuracy possible? I thought it was primarily the barrel, but that chart makes me think there must be a host of factors.

Any input would be appreciated,
Pop

 

[paulosantos]

Welcome aboard. Both cartridges will fit your needs very well. I'll just talk about the 6.8SPC.

Out to 300 yards for hunting, there are plenty of bullets and ammunition from SSA that will work with no problems. The SSA 110 Gr. TSX, SSA 110 Gr. Pro-Hunters, and the SSA 110 Gr. Accubonds.

For target and Varmint Hunting, the Speer 90 Gr. TNT are great bullets that are super accurate and have some great velocities even out of a 14" and 16" barrel. SSA is also coming out with a 90 Gr. OTM bullet that may also be an excellent choice. I got 2900 FPS with the Speer 90 Gr. TNT out of my 14" barrel and it was 1MOA with a lightweight chrome lined barrel. Those Speer 90 Gr. TNT are very capable of 1/2 MOA.

As far as the barrels go, you obviously want an SS barrel. A 16" or 18" would be ideal. White Oak Armament makes great 1:11" twist barrels to your liking. PRI also makes some 16", 18", and 20" barrels that are proven to be very accurate. If you can wait a little bit, AR15Performance is coming out with a 16" 1:11.25" Poly barrel with the DMR Chamber that will be one of the best.

Hope this helps.

 

[ron169]

Well you have a mini conundrum. If I were trying to drive tacks at 600 yards, I would want a 24 in barrel, with a 20 at a bare, bare, bare minimum. Problem with a 24 in barrel is that it is kind of impractical for deer hunting. Too heavy and too long. The thing about that link you posted is that the test was performed in 2007, when many of the companies were using 10 twist, SAAMI chambers. Most have upgraded to 10 twist, or even 12 and 13 twist barrels using SPCII and DMR chambers.

Now as for the question of 6.5 or 6.8. If I were wanting to shoot out of 600 for accuracy, I would prolly go with the Grendal. i havent really seen any of their long range numbers, but they seem to swear by them. I would like to see what http://www.AR15Performance.com could do with a 24 in bull barrel after he laid his hands on it.

 

[constructor]

If you want to punch paper at 600 yds stick with the Grendel but, you will need the CSS match chamber (.295-.296 neck)or similar not the AA chamber. The 6.5 has decent match type bullets that will carry it to 600yds. 100gr lapua minimum, 108gr lapua would be my choice to 600 at unknown ranges or maybe the 107 SMK. 123gr Lapua if at known distances, the 139 is just too heavy IMO.
Again you need a real match grade barrel, not a Sabre, or AA or any other with the standard AA chamber it is too loose in the neck. Lapua bullets are known to be slightly undersized so you need a barrel that is also known to come in small,
Pac Nor comes to mind, 8 twist, 3 groove 22" min, 26" if you can handle it. There are very few guys who really know how to build a benchrest quality AR so ask them all to go into detail about their procedure then compare

If I was competing at 600yds neither the 6.8 or 6.5 would be my choice there are too many others that do it better.
Over 300 I'll use a 6.5-08 Ackley, .243 or 6.5ARSM under 300 I'll stick with the 6.8. JMO
BTW I've had 3 grendels or grendel cats, all true match grade.

ETA- there are 3 match grade barrels on that chart, The MSTN, the PRI and the Noveske, the rest are production barrels.
Paying for match barrels is like buying insurance that you will get a good barrel. Production barrels have larger tolerances some are good some are bad.
I am not building custom rifles at this time.

 

[ma1cyr]

I have an 18 inch SPR and 10.5 inch SBR that are both sub moa. I am using Noveske barrels mated to Larue uppers. My brother has the same configuration in 5.56 and he gets the same result. Take away = a great barrel mated to a top notch upper.

 

[sholling]

It may be worth your while to sign up for a 1 month subscription at Chuck Hawks' site. It's only like $5. He wrote three articles. A detailed analysis of the 6.5 Grendel, a detailed analysis of the 6.8SPC, and a 3rd comparing and contrasting the two. The bottom line was that in his opinion the only long range advantage that the 6.5 may display is with factory loaded rounds, and only because of the bullet design used in factory loads. He stated that the bullet's used in 6.5 Grendel factory loadings were long range target projectiles, while the bullets used in the 6.8 SPC factory loads were hunting projectiles.

 

[Test_User]

That is or should I say was accurate until SSA came out with both the 90 tnt and accubond. Either will shoot inside the Gren out to 600 with same length barrels. If you get a Grendel do yourself a favor and make sure its the longest barrel you are willing to deal with. The grendel doesn't really shine until you get to 24"-28". It doesn't have the horsepower the 6.8 does in the vel department and uses slower powders that need and can use the extra barrel length.

 

[constructor]

He did say 1/2 MOA to 600yds, and didn't say anything about barrel length. The 6.8 does not have a match grade bullet that will do it. That's a 3" group at 600 yds,the 90 would get blown all over. If he had said 16" barrel on both rifles it would make a big difference.
The 6.5 does not have many hunting bullets in the <123gr range The 100 Nosler 120 TSX and 120 Nosler thats it.
IMO the 6.8 is a better combat or hunting round, the 6.5 is a better paper puncher past 400yds.
Would I sacrifice the better hunting bullets and velocity from a short barreled AR to punch paper? No, that's why I don't own a Grendel anymore.

 

[Test_User]

very good point. I agree

 

[Strawdawg]

The way that you two guys stay up all night makes me wonder why you have not developed a couple of rounds and named them the "Vampire" and the "Lycan".....or a derivative thereof. :?: