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Old January 23, 2012, 07:33 PM   #1
markel
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6.5 Grendel vs. the .308

Hey guys,
I am looking to custom build an larger caliber AR-15 and need some input on what caliber to use. From what I have read about the 6.5 Grendel it would seem that it would be more popular give its accuracy and range but I commonly see .308 in both uppers and complete rifles. Why is the .308 more popular? is it a better cartridge? what benefits does it provide? Also if anybody knows who makes good uppers for the 6.5 or even completes please chime in on the discussion. Thank you for your time
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Old January 23, 2012, 08:14 PM   #2
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The benefit of the Grendel is that it fits in a AR-15 lower whereas the .308 requires a AR-10 lower. Check out the Alexander Arms Overwatch uppers.
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Old January 23, 2012, 08:24 PM   #3
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The .308 is also very common and plentiful round, ammo is much easier to find on the shelf and usually a lot cheaper.
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Old January 23, 2012, 08:38 PM   #4
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While .308 is more common, Wolf (don't laugh!) makes a brass-cased 6.5G that costs about $13.00/box on the AA website. I'm facing the same conundrum as to putting together a long-range AR, really leaning towards 6.5G, but there's just so much more availability both for rounds and ballistic information for the .308, so we'll see.
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Old January 23, 2012, 09:53 PM   #5
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Does anyone sell a 6.5 in the typical 6.8 price range?
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Old January 23, 2012, 10:01 PM   #6
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I think you really need to ask yourself if you want a .308 are you willing to step up to a AR-10 build.
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Old January 23, 2012, 10:04 PM   #7
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I am in the process of putting together a 6.8SPC and from all the research I have done, it seems that a quality 6.5G barrel will cost somewhere in the area of $200 more than a quality 6.8SPC barrel and until around 400-500 yards, the ballistics are nearly identical.
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Old January 24, 2012, 09:18 AM   #8
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.308 is a commercial round based on a military based cartridge (or vis versa, but the point still applies), so there's a lot more availability of ammo for sale. It's also been around a while, and is used as a long range precision cartridge by both military and police. All that adds up to a LOT of data, bullets, and powders for the .308 round.

The .308 is going to require an AR-10 pattern platform, which tends to be more expensive than the AR-15, and less standardized. If you go that route, consider getting something that uses the Magpul SR25 / DPMS magazines; that looks to be the most widespread, and Armalite now makes rifles that use those mags also.

The 6.5 Grendel is a cartridge developed for long range shooting out of a standard AR-15 platform. Ammo is limited in selection compared to the .308, but that would be true for almost anything compared to the .308. The pricing isn't too bad, especially given Wolf's entry to the ammo market. It also has recently become a SAAMI standard, so more people should be making the round soon, which may drive the price down on the ammo.

One point of confusion on the 6.5 Grendel is the various chamber configurations out there. To my best understanding, Bill Alexander held the copyrights to the 6.5 Grendel, but let other people develop the Grendel without charge. Alexander Arms then got a new majority stockholder, who tried to make money off of it. Since the copyright was only for the name, Les Baer and others made "clones" with slightly different shoulders and chambers that would still work for the cartridge, and named them differently (such as .264-LBC). With any luck, now that Bill gave the copyrights to SAAMI, that will all shake out, but it is something to think about.

I'd recommend basing the decision on what you've got now. If you don't have a .308, go that route - lots of data, powder and match ammo available, and you can use the round in any number of competition sports. If you already have a .308, then look at the Grendel.
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Old January 24, 2012, 09:59 AM   #9
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I shoot with buds who compete with the 6.5 Grendel in their AR15 rifles.

They best of them shoot outstanding small groups.

Based on the number of malfunctions I have seen, the 6.5 Grendel is not as reliable in feed as the .223 in the AR mechanism.

One real issue is lug cracking. The AR15 bolt is designed to function with .223 loads. The Grendel has a bigger base and I am certain puts more load on the bolt. The fatique lifetime of the bolt is significantally less than a .223. One bud already has had a cracked lug, and he told me of others who have cracked lugs.

For competitors, this is just the cost of using the round, like rebarreling. They just replace the bolt.
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Old January 24, 2012, 10:40 AM   #10
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Quote:
I shoot with buds who compete with the 6.5 Grendel in their AR15 rifles.

They best of them shoot outstanding small groups.

Based on the number of malfunctions I have seen, the 6.5 Grendel is not as reliable in feed as the .223 in the AR mechanism.
I agree, the Grendel mags can be problematic and many need some hand massaging of the feed lips for best reliability. You must have M4 feed ramps because of the over all length of the cartridge. I took a few trips to the range to get my Grendel sorted out and to the reliability I wanted.

There are supposed to be new Grendel mags coming to market that address these issues.



Quote:
One real issue is lug cracking. The AR15 bolt is designed to function with .223 loads. The Grendel has a bigger base and I am certain puts more load on the bolt. The fatique lifetime of the bolt is significantally less than a .223. One bud already has had a cracked lug, and he told me of others who have cracked lugs.
This has been a problem with the G since it's introduction. Some Grendel shooters have increased bolt lug life buy "facing" the upper receiver. This ensures perfect bolt alignment with the barrel extension. Better bolt alignment should give better bolt lug engagement.

If you load for 3000+ fps you increase the chance of a lug cracking.

Between facing the upper and shooting reasonable loads you shouldn't have a bolt issue. Even if you have to replace the bolt every 1-2K rounds it's not that costly, and even 5.56 bolts are a wear item.


6.5 Grendel ammo has become much more available in the past 6-8 months. Hornady and Wolf both offer quality affordable loads now. Wolf is working on a steel case Grendel round that should sell for .30-.40 cents a round. While I wouldn't plan on a lot of "plinking" with my 24" Overwatch barrel, that ammo would encourage me to build a Grendel 14.5" carbine. From my experience the Grendel has a slight edge on accuracy, especially at longer ranges over the 7.62 AR platform.

24" Overwatch barrel/bolt, Alexander Arms upper, ArmaLite NM lower, Vltor Emod A5 with a Vortex Viper.


The 7.62 AR's are going to be heavier, they are propitiatory to a certain extent. Not any cheaper to feed, even good surplus ammo is pushing .50 a round with match grade starting a $1-1.50 a round. I have shoot several different brands of these, all seem to be very reliable and accurate. There are minor differences in fit and finish, some come out of the box well configured and some may need some upgrades. The monolithic upper on the LMT is very nice. Only thing stopping me from owning one is money.

My NoveskaLite AR10. Noveske 21" N6 upper, ArmaLite NM lower, PRS, Atlas, Accu-shot. Waiting for a Nightforce.
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Old January 24, 2012, 11:13 AM   #11
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Quote:
...One point of confusion on the 6.5 Grendel is the various chamber configurations out there. To my best understanding, Bill Alexander held the copyrights to the 6.5 Grendel
The 6.5 Grendel is now a SAAMI cartridge, which will rapidly cause all new production by various barrel and ammunition manufactures to become standardized. I understand that the Grendel trademark is useable by all. This means that anyone can make a chamber to the SAAMI specifications and call the result a Grendel.

The variations in chamber deal only with the throat, leade, and neck diameter. All variations seem to work well with brass cases. The AA neck diameter is a tad larger than most of the others to provide a better balance between accuracy and reliability. The differences in accuracy are more in the category of the size of one-hole 5-shot groups at 100 yards, which is of interest to truly competitive target shooters, but not most hunters.

The larger neck will also better accommodate the steel cased 6.5 Grendel ammunition Wolf is introducing. This development will make Grendel ammuinition as affordable as .308 Winchester.
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Old January 24, 2012, 11:24 AM   #12
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Depends on what platform you wish to build from.
The AR-15 platform is less expensive than AR-10...

For long range target, the 6.5 Grendel is superior to any other chambering for the AR-15 platform, though you'll no doubt hear arguments to the contrary, without merit to back them up.

If I were going with an AR-10 platform, it would be chambered in .260 Remington- not .308, for the same reason of superior long range ballistics.
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Old January 24, 2012, 04:37 PM   #13
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6.5 Grendel vs. .308W

"Why is the .308 more popular?"

So far, don't think anyone mentioned the obvious...

1 - The .308W was introduced (about) 1952, the 6.5 Grendel became a SAAMI round just last year giving the .308W a long head start.

2 - The .308W (7.62X51mm) has been a US standard military cartridge since (about) 1954. A huge advantage and guarantee of being very popular.


"Based on the number of malfunctions I have seen, the 6.5 Grendel is not as reliable in feed as the .223 in the AR mechanism."

Not true, there is NO problem with feeding the 6.5 Grendel in the AR-15. As someone else mentioned, the problem is with the quality of the available magazines. Unreliable mags can be a problem for the .223R also.


"One real issue is lug cracking. The AR15 bolt is designed to function with .223 loads. The Grendel has a bigger base and I am certain puts more load on the bolt.One bud already has had a cracked lug, and he told me of others who have cracked lugs."

This is NOT a problem with the 6.5 Grendel, it can be a problem with ANY cartridge with a larger rim than the .223R. including the 6.8 SPC, .458 Socom and others.

Competitors shooting the 6.5 Grendel who push the cartridge above the limits of the AR-15 are the ones I know of who have had bolt problems.

This can be true of competitors using the .223R. Keep pushing it beyond limits and they can have cracked lugs.


"The fatique lifetime of the bolt is significantally less than a .223."

And what source are you quoting to back up this supposed fact?


"I am in the process of putting together a 6.8SPC and from all the research I have done, it seems that a quality 6.5G barrel will cost somewhere in the area of $200 more than a quality 6.8SPC barrel"

You need to do a lot more research, in fact you need to start over!

Basically the ONLY difference in build costs between two identical 6.5 Grendel and 6.8 SPC are the barrels.

Unlike the 6.8, there are few if any mediocre 6.5 Grendels barrels.

Use a SAME quality, SAME brand barrel on both and there will be little if any difference in price.


"...and until around 400-500 yards, the ballistics are nearly identical."

Internet BS or personal bias... Again, check the ballistics from the SAME (reliable) source. Even with a higher MV the 6.8 has lost that at only around 75 yards.

There is not that much difference at normal hunting ranges but by 400-500 yards the 6.8 is FAR INFERIOR to the 6.5 Grendel.

T.
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Old January 24, 2012, 05:52 PM   #14
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Quote:
The 6.5 Grendel is now a SAAMI cartridge, which will rapidly cause all new production by various barrel and ammunition manufactures to become standardized.
I hope this means they will start selling barrels at a more reasonable price.
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Old January 24, 2012, 07:19 PM   #15
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Bolt Challenges

Alexander Arms specifies a 50,000 psi maximum working pressure for the Grendel. I am told the SAAMI spec is consistent with this level.

Loads from AA, Hornady, Wolf, etc. comply with this pressure ceiling.

Yes, running higher pressures will compromise fatigue life but folks running those pressures are outside of the recommended specifications. The choice of pressure limit keeps bolt life where it should be.

TimW77 captured the essence of the question with the comment that "...who push the cartridge above the limits of the AR-15..." are the ones who experience bolt problems. In the Grendel and other cartridges based on the 7.62X59, the 50ksi limit keeps the bolt thrust more in line with what the AR15 was designed to accommodate.
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Old January 24, 2012, 10:22 PM   #16
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I have about 7000 rounds down 5 different Grendels. Most on my first, 19.5 inch barreled rifle.

All of them have shot very well, with groups in the sub .5 inch range with the preferred bullets in each.

I agree with David Fortier, I can find no reason whatsoever for a .308 in an AR, since I have Grendels. I might be able to find a reason for a .260, but not a .308.

At shorter ranges, the heavier .308 bullets have some benefit, but once you get to 500-600 yards, there is minimal difference.

As for ammo cost, if you shoot surplus ammo, the .308 is cheaper. BUT...most people on this forum aren't looking for volume, but instead for accuracy, and so they will be paying roughly the same cost for ammo. In fact, to match Hornady Factory Grendel ammo in accuracy actually cost more to buy .308!

The truth is that all the ammo will run in Grendel chambers, and most of the variant chambers as well.

With SAAMI approval now, most people will use the SAAMI chamber.
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Old January 25, 2012, 02:05 PM   #17
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Quote:
"...and until around 400-500 yards, the ballistics are nearly identical."

Internet BS or personal bias... Again, check the ballistics from the SAME (reliable) source. Even with a higher MV the 6.8 has lost that at only around 75 yards.
I ain't got a dog in this fight, but I'll toss my 2 cents in.

The ballistics are nearly identical on all modern rifle rounds out to 500. Why do you think so many generic "ballistic drop compensating" reticles are on the market now?

Ballistics describes the path of the bullet in flight, and the curves traveled by the 6.5, 6.8, and even the 5.56 are similar enough that only small rodents would be able to dodge a bullet by the differences. The velocity/energy differences aren't enough to save the life of any animal unlucky enough to be in your cross hairs.

Arguing over incremental increases between rounds in the firearm world is a waste of time. Sure is fun though.

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Old January 25, 2012, 05:45 PM   #18
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I have looked at many charts, they always seem to want to compare 6.5G 123gr bullet to 6.8 110gr bullets but I still say that they are so similar up to 400 yards that you can't tell the difference. If I am missing something, somebody show me where I am wrong.
Also, as for barrels being comparatively priced, show me. I haven't found a good high quality 6.5G for under $450 or so when a good high quality 6.8 barrel will sell for around $250.
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Old January 25, 2012, 06:56 PM   #19
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Quote:
You need to do a lot more research, in fact you need to start over!
Quote:
Internet BS or personal bias... Again, check the ballistics from the SAME (reliable) source. Even with a higher MV the 6.8 has lost that at only around 75 yards.
That's not really what I am seeing here. If anything, comparing the 90gr 6.5 to the 110gr 6.8 it is pretty much the opposite and I can't seem to find data to verify it but have been told that the 90gr in the 6.8 cleans the 90gr 6.5's clock at all ranges.


Here is what I can find as a comparison:
6.5G Speer 90gr TNT:
V/energy: Muzzle 2780/1545, 100yds 2463/1212, 200yds 2167/938, 300yds 1892/716, 400yds 1641/549, 500yds 1421/403

6.8SPC 110gr Vmax
Muzzle 2550/1558, 100yds 2319/1313, 200yds 2100/1077, 300yds 1893/875, 400yds 1700/706, 500yds 1524/567

6.5G Nosler 120gr Ballistic tip:
Muzzle 2520/1693, 100yds 2334/1451, 200yds 2155/1238, 300yds 1984/1050, 400yds 1822/885, 500yds 1670/743

Hmm, looks like a pretty close comparison to me. The 6.5G stats were from Alexander Arms website and the 6.8SPC was from Hornady.

Last edited by CTS; January 25, 2012 at 07:03 PM.
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Old January 25, 2012, 07:12 PM   #20
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To me, the effective differences are fairly clear.



For similar barrel lengths between the SPC & the Grendel (and the issue M14).
The Grendel velocities come from my own rifle.
The SPC came from here:
http://www.frfrogspad.com/68spc.htm (with a little charity delta-V added)

Ship me other bullet suggestions and I'll run them.

Last edited by mehavey; January 25, 2012 at 07:22 PM.
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Old January 25, 2012, 07:48 PM   #21
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How about using the same ones I did so that we can see how your program compares to factory published load data? Of course you are showing trajectory and not downrange velocity and energy so it still doesn't help much.
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Old January 25, 2012, 09:01 PM   #22
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Here you go:



The 120gr Grendel cleans the 110SPC's clock -- about the same as the SPC cleans the 90gr Grendel.
(It's a mass/energy retention thing all round.)
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Old January 25, 2012, 09:35 PM   #23
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Interesting. I would love to know what rifling twist and barrel length these are based on. Is that something you enter yourself? I have heard the 6.8SPC velocities have improved greatly since they started using a slower twist rate of 1:11. It would also be nice to see the two with the same weight bullets.
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Old January 25, 2012, 10:13 PM   #24
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My Grendel is 1:9 and I'm getting 2,575fps (Oehler chrono'd) out of a 19.5" barrel using commercial (AlexArms) 123gr Scenars. (Handloads are hitting 2,550-ish).

Good ballistics/info for the 6.8SPC is found heree:
http://www.frfrogspad.com/68spc.htm

and here:
http://www.bvac-ammo.com/images/pdfs...isticsData.pdf

...both of which are consistent with other published/DoD values.

Comparing the two should start with usable case capacity after the bullet is seated to magazine length. The Grendel using a 123gr anything gets to use about 28.0gr H2O case volume. The SPC optimizes on ~115gr bullets leaving 27.6gr H20 volume. This lighter-weight bullet enables the .277 SPC to roughly hit/equal the heavier-weight .264 Grendel velocities, but at the cost of a much less ballistically-efficient projectile at range
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Old January 25, 2012, 10:24 PM   #25
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THE OP DIDN'T ASK ABOUT THE 6.8.

The issue is this:

Quote:
From what I have read about the 6.5 Grendel it would seem that it would be more popular give its accuracy and range
And as was already said, it would do well to study the ballistics of each quite a bit more. The simple fact is that most data given on calibers are not baselined with the same rifle, barrel length, or ammo. You get a variety of each, and some study is needed to sort out the bias, BS, fanboyism, marketing, and agendas.

Companies who sell any of the guns and ammo are generally held in respectful suspicion, after all, they are trying to sell you something. Fanboys generally exhibit the affects of testosterone poisoning, it's entirely a locker room measuring contest to them, data is what it's all about.

From the perspective of what tool is better, here's the straight scoop: in the AR, the 6.8 is a great killer under 500m, the 6.5 will punch paper very precisely out to 600m, and the .308 will still kill people at 850m. If you try to use any of them for a different purpose, be very sure you are going to have to accept compromises, understand what they are, and whether it's going to affect things adversely. If it's a matter of exploiting the optimum performance, none will do what the others do. They are all designed and purpose built to do different things, and none can hold a candle to the .50BMG.

Of course, no one would want to shoot one of those from a 14.5" barrel for a full 30 round mag, either.

IBTL.
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