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OK I have searched and cant find an answer to my question..
I am going to build a long gun on the AR platform and was wondering about the upper. I know DPMS has a specific .308 upper but i'm wondering do I actually need it?
I was going to go with a 24" Bull Barrel, DPMS lower with the Timmy Style drop in trigger group etc. The upper is what i'm wondering about. Can I get a stripped upper
and build it like my CQB weapon or do I have to have the .308 spec upper? Same question for the 6.8. I am finding this a cheaper alternative to building a .338 or
buying a Anzio lightweight .50. Also i'm a machinist so if I need special parts that you cant buy I can make them. I was going to make my own suppressor and my
own Flash Hider.

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You'd have better luck and more responses by posting here:

http://www.ar15.com/forums/f_3/121_AR_Variants.html

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You will want to get that in writing from the NFA branch.  Last I heard you were not allowed to have extra baffle stacks.  It doesn't matter what someone on the phone tells you.

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Yes, a .308 is a totally different lower.

The 6.8 was designed to fit as much kick ass in the existing lower as they could in combat length or shorter barrels.

FWIW, I do shoot my 6.8 at 750 yards, and there are guys that go 1,000 yards with it. It isn't that bad at all, especially with the 140gr Berger load from SSA. It is supersonic past 1,000 yards from a 16 inch barrel. It's more than doable.

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6.8 is not a 1,000 yard weapon regardless of what Pavlovwolf and the 6.8 fanclub says.  The.308 is not even considered a 1,000 yard gun in some circles but it is far more capable than the 6.8 at long distances.

Is it possible to hit things at 1000 yards with the 6.8?  Yes.  So can a .223 with the right bullet and shooter.

Is 6.8 the correct tool for the job that will perform in varying environmental conditions at that distance without potentially dangerous hot-rodded ammo? No, not even close.

.308 and the sister calibers are not compatible with AR15 type lowers.  Get a .308 caliber lower and build your rifle for this purpose.

If you want 1,000 yard+ capability, then I would really recommend looking into the .260 Remington or 6.5 Creedmore.  DPMS does chamber 24" uppers in these calibers.  For factory ammo, I would look into HSM for the .260, but the rest of the factory ammo in this caliber leaves a lot to be desired.  6.5 Creedmore has the Hornady and a few other match grade loads available so it might be better if you don't roll your own.

The DPMS/SR25 platform has Magpul magazines and the DPMS .308 lower has the most interchangability of the .308 variants (CMMG, DPMS, Knights, POF, & several others).  The Armalite AR10 platform is another option but mags are going to be more expensive and uppers are more proprietary but high-end custom shops typically can build them.  

If you really want a 1,000 yard gun semi-auto you should check out GA Precision.

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Wolf, don't waste your time with tool bags.

For the OP, I believe you have found some good answers. The 6.8 is good for hunting out to 400ish yards, a little bit longer for the .308. You will need dope on both if you are after game at those ranges. Both can engage targets much farther, depending on how much elevation your glass has.

Read up on the NFA stuff for sure or get those statements in writing. The ATF doesn't play around.

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OOPS!!!

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Yea i'm finding that the ATF and NFA have different opinions on the same subject. I was the same when I was in the Navy. We learned about the correct way to use breaching charges from our chief then the NEW LT came in and wanted it done a totally different way. Needless to say the chief had been in combat situations before and the LT had not. Same old shit i guess.

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The 140gr Berger VLD was tested near SSA's headquarters, so that is close to 1,000ft above sea level. I don't know the temps since I can't remember the exact date Art tested it.

Per Art, from 68forums

Default

The rounds were shot from a 1-10 and 1-11 twist semi autos, the range we were at only goes to 800, all ballistics were from a 1-10 twist 16" barrel. From a 18" I would guess the velocity will be around 2,500 FPS. With the 1-10 the round is still super sonic pass 1,000. We loaded then out to 2.295 so you need to have the right mag.


Art - SSA

FWIW, on 68forums, pretty much every single bullet is actually drop tested to get the real BC numbers. We have revised them both up and down for different bullets. Those real numbers are posted, but as the site is down for maintenance, I can't retrieve the data.

That ammo has been tested by multiple people, and it has given at least 2400fps from a 16" and in many cases actually closer to 2450fps in the 1/11 twist, and the ARP barrels.

Also, before someone cries about special magazines, only one maker now holds less than 2.295 and that is Barrett. C Products Defense is out with ones that hold 2.305, and they are only $13.99 at a few retailers, and $14.99 everywhere else. There are tons of them out there, and I have two coming in tomorrow or Thursday. They have been receiving excellent reviews, and nobody has had an issue with function, other than the very first batch, where a few got out with bad coating. All of those have been replaced, and the replacements are perfect.

BD, you can fuck with the numbers all you want. The temp, or the elevation isn't going to change anything more than a few fps, and they are still more than fine with high heat, or low cold. Hell, my" unsafe" dynamite loads ( 90gr TNTs at 2925fps, and 110gr Hornady OTM at 2700fps)  have been shot on a farm, in close to 100f heat and unGodly South Carolina humidity, after the gun, with the ammo in the chamber, and full mags were laying on top of a mat in the field, and, after some rapid fire strings. Guess what. I still have all my fingers and toes, and none of the ammo showed any flat primers, swipes or anything else. Even in the extreme heat, the ones that were fired at the end of the strings had very slight swipes. The 5.56 guns that were there that day, were showing much more than what I had. No popped primers or anything, but they had some cases that had ejector marks, with ammo that normally didn't unless under rapid fire. The rifles they were shooting were Colts and Spikes, and one Olympic with a Wylde chamber ( which is rated for 5.56 ), and a Bushmaster. They also had a few bolt guns.

OK, now let's get down and dirty.

The 6.8, though fun at 1,000 yards, is not what I would chose if I had a choice. If I had a 6.8, and a .308 right now, and Trevor "farmer boy" called and asked if I wanted to come out and shoot at the farm. I would ask what field. If he answered the 750 yard or the 1200 yard field, I would ask how far we would be shooting. If we were doing mostly 500 and back, maybe with a little 750s ( which I have shot ), and maybe a couple of 1000 yard targets, I'd take the 6.8. If he said, we were going to go and set up for 750 or 1000 or 1200 mostly, I would take the .308 and pray at anything over 1000 yards. If it was windy, I'd pray at all ranges. If it was windy, I would likely take the .308 over the 6.8 at 500 yards even if that was about all I was shooting.  

Now, I don't have the cash to buy anything more suitable for 1000 or more, nor do I currently own anything. If I did, I would go that route if I was shooting more of that than anything else.

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You guys are soooooo right!  I have seen the light.  I am selling my entire gun collection now and repurchasing a single 6.8 for all my shooting needs.

You have educated me through your informative posts that the 6.8 is a 1,000 yard gun which outperforms the .308 all day, meaning that the Marines will now be downsizing their M24's from the .308 instead upsizing to the .300 Winchester Magnum because of the .308's performance issues in different environments and conditions they are likely to encounter at 1,000 yards.

One ballistics chart done by the company selling the cartridge has completely changed everything I know about ballistics and F Class shooting.  My own ballistic charts from JBM showing things like barometric pressure and temperature creating transsonic destabilization before 1,000 yards is irrelevant because it is "only a few fps difference" (even though the drop from 950-1000 yards is about 5.5 feet and the destabilization won't throw the accuracy off at all). Plus I have learned that ballistic coefficients are absolute constants and never change with velocity differences.  Boy did I learn a lot from you guys!

I am also in awe of the 140 grain Berger's superior windbucking ability and additional 10MOA of drop (requiring 47+ MOA of elevation adjustment) is going to make it the top choice for all distance loads vs. anything in the .308 platform.  I guess the AR10 and .308 AR platforms are now obsolete and useless because of this load.



Sarcasm aside, the personal bias and belief that the 6.8 is the greatest round ever makes a thread citing a very good round for the 6.8 AR platform into a crapstorm of misinformation and rhetoric that is not based on personal experience but suppositions and uneducated assertions.  The .308 is typically considered an 800 yard platform out of a 20-24" bolt action even though it is much more capable beyond that with some rounds in the right conditions.  

Being lucky enough to get the one magic factory load or one magic bullet capable of that distance to shoot in your rifle accurately and consistently is going to be a challenge and doing it over varying conditions is another challenge altogether.  This is why I have adjusted pet loads for different environmental conditions on my .260.  The temperatures here go from 0-110 degrees depending on the season and it does in fact change your ballistics and accuracy node considerably and in certain conditions my distance capability gets severely diminished.

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Well I finally got someone with some sense on the phone at NFA Virgina. On the suppressor issue its kinda a grey area. I was told the local office could look one way or they could look the other way. Technically any part of a suppressor is considered a suppressor so even tho the baffles are not SN# an agent could technically say they were a separate suppressor. The way around this whole mess is to get my FFL, SOT and MFG license then I can make what ever and however many I want. Man they make it a pain in the ass! Good news is right now according to Mrs. Steely and the NFA its not a long wait on getting all the stuff I need but a tax stamp is 6 to 8 months out. FFL, SOT and Mfg will only take a little under 3 months. What a pain!

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You guys are soooooo right!  I have seen the light.  I am selling my entire gun collection now and repurchasing a single 6.8 for all my shooting needs.

You have educated me through your informative posts that the 6.8 is a 1,000 yard gun which outperforms the .308 all day, meaning that the Marines will now be downsizing their M24's from the .308 instead upsizing to the .300 Winchester Magnum because of the .308's performance issues in different environments and conditions they are likely to encounter at 1,000 yards.

One ballistics chart done by the company selling the cartridge has completely changed everything I know about ballistics and F Class shooting.  My own ballistic charts from JBM showing things like barometric pressure and temperature creating transsonic destabilization before 1,000 yards is irrelevant because it is "only a few fps difference" (even though the drop from 950-1000 yards is about 5.5 feet and the destabilization won't throw the accuracy off at all). Plus I have learned that ballistic coefficients are absolute constants and never change with velocity differences.  Boy did I learn a lot from you guys!

I am also in awe of the 140 grain Berger's superior windbucking ability and additional 10MOA of drop (requiring 47+ MOA of elevation adjustment) is going to make it the top choice for all distance loads vs. anything in the .308 platform.  I guess the AR10 and .308 AR platforms are now obsolete and useless because of this load.



Sarcasm aside, the personal bias and belief that the 6.8 is the greatest round ever makes a thread citing a very good round for the 6.8 AR platform into a crapstorm of misinformation and rhetoric that is not based on personal experience but suppositions and uneducated assertions. The .308 is typically considered an 800 yard platform out of a 20-24" bolt action even though it is much more capable beyond that with some rounds in the right conditions.  

Being lucky enough to get the one magic factory load or one magic bullet capable of that distance to shoot in your rifle accurately and consistently is going to be a challenge and doing it over varying conditions is another challenge altogether.  This is why I have adjusted pet loads for different environmental conditions on my .260.  The temperatures here go from 0-110 degrees depending on the season and it does in fact change your ballistics and accuracy node considerably and in certain conditions my distance capability gets severely diminished.

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We said it could do 1000y & still have 1000fps. We didn't say it was the best 1000y cartridge on the market. Also, we showed the pressure tests of the factory ammo.
We backed up what we said. You didn't. So, look who's calling the kettle black. So, SSA are misinforming & making uneducated assertions. I'd call that slander/libel. Unless you can back your claims & assertions up with data.

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You 6.8 guys are incorrigible.  If anyone disagrees with you, you resort to childish name calling like "tool bag" and "fucking nut job" and saying that I am libeling/slandering someone?  

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You are assuming a powder sensitivity that may not be there. Many of the powders that we have been using are not very temp sensitive at all. I have shot several of my loads throughout the year that vary no more than 10fps from the 100f temps, to the 20f temps that we have here occasionally. Nothing I shoot is sensitive at all in regards to the powders I use for my 6.8 loads .

Now, if I were to go back to the .308 loads I used to use, one using BLC-2, there were big swings. In that case you would be right. I got really kooky swings with it. I didn't like it at all. I went to IMR 4064 and it lessened things a good bit, but I was still getting 25fps differences in the lowest and highest temps.

My 6.8 loads though, with the H322, and the Re7, are very, very stable regarding temps. I have not yet chronographed the AA2200 in extreme temps, but I have some Nosler 110gr ABs that I am saving for that purpose. Of what I have tested, the Re7 90gr TNT was the most sensitive, with about 15fps between a 27F day, and a 101f day. I went from 2925fps with the 90gr TNT, down to 2905fps. That is not a drastic difference, and the poi is changed very little. Both days were had high humidity, and it was raining one, and sleeting the other.

The H 322 was less sensitive. But it was in a 30f day versus a 100f day. It was single digits in difference. The 110gr Hornady OTM was 2705fps in the 100f, and 2697fps in the 30f day. Both days were dry, although the 100f day was very humid as it tends to get around here in late summer.

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In reference to the libel/slander. I was talking about you stating their load was dangerously over pressured.But, that's up to SSA.  I showed the pressure data, eluded to the similar pressure with the M855A2 round & gave the usual 6.8 proofing pressure load in countering. So, I'll leave it there.

Thanks for sharing the data.
Ah, 32.6 & 31.2 MOA with a 100y sight in & still over 1000fps @ 1000y. Not too shabby!!
Like I said before The 6.8 isn't the best round at 1000 yards. But, it will do quite well.
I'm not going to lower myself to name calling.
Say what you will. I don't care. I've probably hear it before anyhow. :rolleyes:

The 6.8 is what it is. A dang good multipurpose intermediate round, designed for carbine-middy barrels (But, does very well with longer & shorter barrels too.) that can crossover in other areas!

Now, what was the OP?

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6.8 is not a 1,000 yard weapon regardless of what Pavlovwolf and the 6.8 fanclub says.  The.308 is not even considered a 1,000 yard gun in some circles but it is far more capable than the 6.8 at long distances.

Is it possible to hit things at 1000 yards with the 6.8?  Yes.  So can a .223 with the right bullet and shooter.

Is 6.8 the correct tool for the job that will perform in varying environmental conditions at that distance without potentially dangerous hot-rodded ammo? No, not even close.
.308 and the sister calibers are not compatible with AR15 type lowers.  Get a .308 caliber lower and build your rifle for this purpose.

If you want 1,000 yard+ capability, then I would really recommend looking into the .260 Remington or 6.5 Creedmore.  DPMS does chamber 24" uppers in these calibers.  For factory ammo, I would look into HSM for the .260, but the rest of the factory ammo in this caliber leaves a lot to be desired.  6.5 Creedmore has the Hornady and a few other match grade loads available so it might be better if you don't roll your own.

The DPMS/SR25 platform has Magpul magazines and the DPMS .308 lower has the most interchangability of the .308 variants (CMMG, DPMS, Knights, POF, & several others).  The Armalite AR10 platform is another option but mags are going to be more expensive and uppers are more proprietary but high-end custom shops typically can build them.  

If you really want a 1,000 yard gun semi-auto you should check out GA Precision.

ETA:


The way I read this, you are saying the 6.8 is a 1,000 yard gun.  I don't believe that a 16" 6.8 is a 1,000 yard gun despite the claim above and on SSA's website I don't see the 140 grain Berger load that is doing what you say.

The Marines are now converting their M24's to 300 Win Mag because they concur that the .308 doesn't have enough conistency across the potential environmental conditions they encounter and thus they consider it an 800 meter platform from a bolt action.

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Seriously, you are accusing me of libel (the written form) from the above?  And I am accused of lacking in the reading comprehension skills?

The average max pressure posted on SSA's load was 58,700 PSI.  Again that was the average and the temperature outside was not listed on the test sheet.  SAAMI, which is the only standardized and approved pressure limit is at 55,000 PSI, and SPEC II's are typically stated to be between 57,000 and 58,000 and sometimes up to 59,000.  With no concrete standard, they can load to whatever pressure they want and so can handloaders.

Over and over and over and over I have stated that in order to CONSISTENTLY get a load to perform at 1,000 yards in ALL ENVIRONMENTAL CONDITIONS, you would have to actually FAR EXCEED SSA's load which is too high for 6.8 chambers and on the cusp of the SPEC II's generally accepted top pressure end.   Also, after being accused of lying and libeling by you, I show 2 ballistics tables with minimal environmental changes of that load not performing supersonically at 1,000 yards.

Lastly, you might want to inform yourself about the speed of sound.  It is not 1,000 fps and bullets typically start to destabilize just prior to reaching the subsonic threshold as the pressure cone at the nose of the bullet becomes inconsistent.