doing a 6.8 upper(maybe)

[dhdoug]

i am hoping for some guidance/input from a few of the AR gurus from INGO. so here goes....i have a lower(spikes) that is marked "multi" and have the parts kit installed. no stock kit yet as i wasnt sure if a different caliber than 5.56 would effect the buffer and such. but the real issue(s) is.....can a 6.8 upper go with on this lower? if so, are magazines the only other item that "changes"? sure would appreciate any help. thanks.

 

[melensdad]

Yes you can put a 6.8 Upper on any lower, even a lower that is marked for 5.56. No need to change the buffer or spring.

C-Products makes dedicated 6.8 magazines.

Given the shortcomings of the 6.8, I have to ask what will the purpose of the rifle be once you convert it?

 

[Duce]

Short comings of the 6.8 ????? Would you care to expand on this, possibly in another thread so we don't jack this one? Duce<><

 

[sp3worker]

Short comings of the 6.8 ????? Would you care to expand on this, possibly in another thread so we don't jack this one? Duce<><

I'm wondering as well. I considered building one up to use as a light antelope/deer rifle.

 

[melensdad]

Oh its a good deer rifle but not here in Indiana. Basically its a modern 30-30 and a 30-30 is certainly an excellent whitetail round at modest ranges.

Not sure it would be a particularly good antelope round as it is basically a short range round and runs out of energy pretty quick. Its not uncommon to take antelope at long ranges and the BC of the 6.8 bullets are miserable, it drops below 1000 ft lbs of energy at 225 yards and velocity drops off quick too.

Not many bullet choices.

Not a particularly good varmint round as lightweight bullets choices are sparse and actually a 5.56 is probably a better varmint round.

Not a great coyote round because its not well suited to long range shots, but it certainly could take feral hogs with ease.

Simply put there are much better choices than the 6.8. The 6.8 gained popularity because the publicity with the military trials, no doubt that it would be a great Close Quarters Battle round beating out the 5.56. But unless you are building a CQB rifle then I don't much see a lot of logic for the round given the poor ballistics and slim bullet choices.

 

[malern28us]

Dont forget that 6.8 ammo is ungodly expensive! I love mine but hate the ammo cost. You can get 7.62x51 ammo cheaper!!!

 

[Duce]

Doesn't 6.8MM=.270"?
I see your point though sounds as if you want a larger caliber AR, you'd be better off going 7.62X39 route.
Given the cost of AR uppers you may be just as well picking up an AK.
Thanks..Food For Thought..Duce<><

 

[melensdad]

Doesn't 6.8MM=.270"?

Yes, but you don't have the ability to use all the bullets that are designed for the 270 because you have the limitation of the overall length that will feed and function in an AR. There is a long case body so the bullets required must be fairly short and light to function. Factory loads run between 85 to 115 grain bullets (a 26% spread in weight). I know of only 4 factory loaded weights available (85, 90, 110 and 115). That is not a wide range of weights and the highest ballistic coefficient bullet is the 115 grain and that has a very poor BC.

To put that into perspective, factory loads range from 90 to 144 grains for the 6.5 Grendel (37.5% spread in weight). I know of 7 factory loaded weights available. While factory loads range from 45 to 77 grains for the 5.56 NATO (42% spread in weight) with at least 8 factory loaded weights available. The wider the weight range the greater the choices of bullets available for various purposes from varmint to bad guy to various game sizes.

 

[malern28us]

UM...wrong. 85gr, 95 gr, 97 gr, 100 gr, 110 gr, 115 gr...can load your own 120 gr and 130 gr....will fit in AR mag. If you have questions refer to ..::68FORUMS::..

 

[melensdad]

UM...wrong. 85gr, 95 gr, 97 gr, 100 gr, 110 gr, 115 gr...can load your own...

OK there are a few more middle weight bullets than I am aware of but the bottom to top spread is still only a 26% spread. That is pretty meager.

Obviously with handloads many things can be done but that is true with ANY round, but for factory loads you list a couple that I have not seen. However the ballistic coefficients are still horrible and the rounds still drop below 1000ft lbs of energy at only 225 yards. That is simply not an adequate range for game like antelope (which was mentioned as a possible use for the round in one of the early posts) which are often shot a 400, 500, 600 yards and beyond. Now you don't need 1000 ft lbs of energy on an antelope but it would probably not be too ethical to go below 800 ft lbs of energy on game like that.

So with a 115grain bullet the 6.8 runs below 800ft lbs at about 435 yards, which is the shorter range that is typical for antelope. In contrast a 243 WSSM will push to probably 800 yards and still retain 800 ft lbs of energy with a hunting bullet ... almost double the effective range of the 6.8. While a 6.5 Grendel will carry a 120 grain hunting bullet out to 700 yards and still have just over 800ft lbs of energy, so the Grendel is not up to the range of the 243 WSSM but still offers much more effective range than the 6.8spc. Clearly some hunters will shoot an animal with at lower bullet energies but many simply consider it unethical.

Why do I stress the range distances for antelope? Simply because there are many recorded 1 shot antelope kills at 1000 yards and beyond. Antelope are shot on the plains and in areas where there is no cover so shots are typically very long.

One of the things that I find interesting with the 6.8 is that people do load them to some very high pressures, and flattened primers or cupped firing pin strikes are common. Those are danger signs for reloaders but seem to be common with 6.8 loads. I don't know why people keep trying to put 20# of **** into a 10# bag but that seems to be commonplace with some of the 6.8 loads.

 

[sp3worker]

So with a 115grain bullet the 6.8 runs below 800ft lbs at about 435 yards, which is the shorter range that is typical for antelope.

Why do I stress the range distances for antelope? Simply because there are many recorded 1 shot antelope kills at 1000 yards and beyond. Antelope are shot on the plains and in areas where there is no cover so shots are typically very long.

I've shot 4 antelope, longest shot was a little over 300yds. I was going to start using my muzzleloader to make a little sport of it, but would like to get one with an AR type rifle too. After seeing the #'s on the 6.8 I might think about another route. The 6.5 sounds pretty good. Are there many factory hunting type rounds for it?

 

[melensdad]

The 6.5 sounds pretty good. Are there many factory hunting type rounds for it?

Not a lot but a few. I'm not advocating any one round. Just pointing out there are alternatives.

However to answer your question, in factory loaded 6.5 Grendel ammo, Wolf makes a 123 grain soft point that is pretty good and cheap, I've gotten it as low as 50 cents a round delivered to my door but its scarce since one of the Wolf plants went KaBoom! Other factory loads include 120 grain Noslers, 120 grain Barnes Triple Shocks and 129 grain Hornady and 130 grain Swift loads suitable for hunting. There are lighter weights also.

Honestly I think the 243 WSSM is under appreciated in the AR platform and that really has some potential. Realistically it can't be pushed too far in the AR15 platform by handloaders because of overall length limits, but for people who don't handload the factory loads are more than suitable for long range hunting.

Mind you I'm not saying the 6.8 is a bad round, in fact out to a couple hundred yards its all positive. And for a whitetail round its going to be a killer round in states where it is allowed. Its just that it realistically cannot be pushed out too far because the energy numbers drop off pretty quick.

 

[Duce]

Melensdad: Thanks for the insight put forth in a professional manner......Now how do you give the guy rep points??????....Duce<><

 

[kwatters]

Melensdad: Thanks for the insight put forth in a professional manner......Now how do you give the guy rep points??????....Duce<><

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