Alternative AR 15 chamberings

[dakota.potts]

In my constant fantasizing about guns and such (if only I had money) I like to do a lot of research on the things I'll end up buying.

I'm wondering what cartridges are available for an AR 15 that would well by simply swapping out an upper receiver or a few pieces.

One in particular that interests me is the 6.8mm SPC.

I'm looking for something in between 5.56 and .308 in terms of power, recoil, range, and price. A .308 is more than I want and more expensive. But I want something that would have a little more power than a 5.56 and maybe go out to ranges a little farther if I wanted to take it out shooting longer ranges.

Are there any calibers available that are relatively easy to do this with without paying $1.50 a round? Will the options increase if I reload?

 

[tahunua001]

6.5 grendel is better for long range shooting and hunting. 6.8 is better for up close and personal combat and more readily available ammo.

if I ever get an alternative caliber(besides the 9mm that I already own) it would be 6.5G.

the 6x45(243 bullet in a 223 casing) interests me too but finding barrels for them is a huge pain in the rear.

 

[Tejicano]

I am a big proponent of the 6.8 SPC round. For my interests it is about optimal in bore diameter, bullet weight, and muzzle energy for a round that can be properly staggered in a magazine which fits in the standard AR-15 magazine well. In addition is it quite accurate and designed for optimal velocity out of shorter barrels - it doesn't give up so much velocity out of a short barrel.

I have three firearms in this caliber - a plain-Jane 16-inch barreled "M-4" type, A custom ordered Bison Armory carbine, and a 11.5-inch barreled AR handgun.

In fact the only AR I have in 5.56mm is a "Retro" model built like the M-16A1 I carried in the Marines.

I never cared so much for the 5.56 round. 7.62X39mm is cheaper but the only high capacity magazines that function reliably with that round out of a standard AR have to be un-naturally curved and almost "bent" forward from the mag well.

The 6.5 Grendel is a great round but its designed more for accuracy from longer barrels and high-capacity magazines either nave significantly fewer rounds or don't fit standard mag pouches.

 

[dakota.potts]

How available/expensive is 6.8 ammo? I don't reload, though I think I probably will start if I get into a rifle either way.

It seems that the 6.8 is built to swap onto a 5.56 lower with no issues.

With this in mind, would I be better suited buying a 6.8 rifle with a spare 5.56 upper or a 5.56 rifle with a spare 6.8 upper? One of the things that interests me about the AR platform is the ability to swap rounds fairly easily.

What other calibers can go onto a 5.56 lower with no modification?

 

[Theohazard]

What other calibers can go onto a 5.56 lower with no modification?

My favorite alternative AR-15 caliber is the 300 Blackout. I doesn't have the range or power of the 6.5 or 6.8, but in supersonic form it pretty much matches the ballistics of the 7.62x39mm. And in subsonic form you have a 220+ gr. bullet that can still cycle the action of the rifle, has a much better ballistic coefficient than any pistol round, and is super-quiet when suppressed. But what I like most about the 300 Blackout is that it uses all the same parts as a 5.56 except for the barrel. It even uses the same mags, which is extremely convenient.

 

[MJFlores]

Ya know....I would absolutely love it (just from a hunting standpoint) if someone would try chambering a 35 Rem on an AR platform. I would think it wouldn't be overly complicated as I believe the bolt face for a .308 could be easily machined for the 35 Rem case. A 35 cal barrel would be screwed on, and maybe?....do 35 Rem cases fit in a .308 magazine? It would be close although 35 Rem magazines would probably have to be manufactured meaning the idea would probably never occur. Recoil would be about the same as a .308 although with a piston system you could dial down eliminate too much force on the carrier group during cycling. Being able to cycle and fire a 200 grain 35 cal bullet from an AR platform to me would be a wonderful thing, as far as hunting is concerned. Maybe someday.

 

[dean1818]

I went with a Bison Armory 6.8.

I am very happy with the rifle.

3 friends bought the same rifle after I bought mine.

If you are thinking about the 6.8, call Ben, the owner of Bison and ask about the round and the rifle. He is a great guy.

Tell him Dean from Dallas said to call


The rifle is very accurate, and I use it on wild boar here in Texas.

Using the Hornady 120g SST, all but one of my shots have been DRT

Its a thumper of a round. It will give you 1k ft lbs out to 275 yards


The only downside of 6.8 is ammo cost. You can find deals for $1 per bullet, but you have to look for them. I reload, so my cost is around $.30 a round.

There is availability of 6.8 on shelves, but limited choices.


If you plan on a SBR and /or surppresed use, the 300 is a logical choice
The hunting range is significantly less than a 6.5 or 6.8
Factory ammo availability is very spotty and almost always over $1.25

The one you should also look at is the 6.5 as mentioned above

I havent shot one yet, but they are getting impressive performance

But....... Almost no availabilty of ammo(for now)

 

[Fishbed77]

With this in mind, would I be better suited buying a 6.8 rifle with a spare 5.56 upper or a 5.56 rifle with a spare 6.8 upper?

It doesn't matter. It would probably be easier and less expensive to buy a 5.56mm rifle and get a 6.8mm upper.

 

[globemaster3]

I've purchase several rifles for my kids in 6.8. At the same time, I also purchased separate, matching uppers in 5.56. The theory was if equipped with the same scope/bipod, they could practice with the cheaper 5.56 and swap to the 6.8 for hunting.

Thus far, my oldest has tipped over 3 deer with hers using Hornady's 120 grain SSTs. All shots inside 100 yards and all DRT.

The challenge with most alternative AR calibers is ammo cost/availability. I am currently paying just over $1 a round for ammo, but I've seen more expensive offerings out there. I buy either Silver State Armory or Hornady. Federal is producing an MSR for 6.8 and at last check, it's coming in at $24/box.

I've seen 6.8 on the shelves at Cabellas, my LGS, but strangely, never at BPS. Lots of places to either order online or my LGS orders it for me.

One thing is for sure, when I start reloading, it will be for this cartridge first!

Another thought is .243 or .25 WSSM. I still see ammo around and there are a couple companies producing rifles for them. Just a thought.

And before you completely rule out .308, I shoot a DPMS LR-308B that I purchased new for $900. I still see them on GB for~950-1,000. That's not too much from a mid-tier AR-15. It's slick sided, but for my hunting uses, it's worked fine.

 

[MarkCO]

Don't count out the .450BM, 300BO, 30 Remington AR. For medium range cartridges, they have some great appeal.

 

[Mobuck]

I gave up on the 6.8 due to ammo availability issues. I added a 300AAC and another 7.62x39-at least I can get ammo and/or reloading supplies for those.

 

[ripnbst]

People talk down to the .300 BLK a lot. It can be shot effectively to 700 yards using supersonic loadings. I'm not a fan of alternative calibers because I can't ever find any of them for a decent price 6.8, .300BLK, 6.5G, et al.

 

[dakota.potts]

The 6.8 and 6.5 sound close to what I'm looking for -- more punch, higher velocities, better ballistics, less recoil than a .308 or such.

Both seem relatively expensive, even reloading, and the low ammo availability concerns me.

The .300BLK doesn't do as much as I want but seems to have higher muzzle energy at close range. It would be cool if I were going the NFA route, but I'm neither old enough nor looking to spend that much money yet. I might see an 8 or 10 inch suppressed AR in .300BLK appearing in my future though

I am curious about how hard it is to swap over to a 6.5 Grendel? Will just an upper do it or do you need to swap more?
I'm also hearing that although a 6.8 will fit in an AR magazine, manufacturers are recommending only loading 5 or 6 at a time or else it will bulge? Can anyone confirm?

Also, did Tula ever come through on the cheaper 6.8 ammo they promised?

 

[dayman]

.458 SOCOM fits in standard mags (a 30 round 5.56 mag becomes a 10 round .458 mag), and only requires a new upper.
It's less of a long range option than 6.5/6.8, but if you're just looking for raw stopping power (as in stopping a truck) it's hard to beat.

 

[MJFlores]

I wonder...could you screw a 35 cal barrel chambered in .358 winchester on to an AR setup for .308 win and run the 358 Win through it? Same bolt face, same cartridge length, should fit in .308 magazines. I would think yes?

 

[Rascall]

I'm also hearing that although a 6.8 will fit in an AR magazine, manufacturers are recommending only loading 5 or 6 at a time or else it will bulge? Can anyone confirm??

That's odd...I load all my 6.8 mags to capacity with no problems. But then, I'm putting 6.8 cartridges into 6.8 mags. What you describe is what happens if you try to use the wrong mags.

Rascal

 

[globemaster3]

If you try running the 6.8 in 5.56 mags, then as has been mentioned in other threads here, it can be a concern with the mag bulging.

However, I have always used 6.8 mags, and all 5 rounders (purpose built hunting rigs) and have never had a problem.

 

[dean1818]

I load my 6.8 mags to the hilt

Not a problem


Tula talked about a 6.8, but never delivered



Another option if you dont reload

There are deals for just under a buck per bullet for 6.8 for gunbot

You can get $.40 to .50 a piece for brass, by selling it

Net price.... under 50 cents

Read 6.8 forums.... many gurus and great people

And you can sell your once fired brass

 

[Theohazard]

That's odd...I load all my 6.8 mags to capacity with no problems. But then, I'm putting 6.8 cartridges into 6.8 mags. What you describe is what happens if you try to use the wrong mags.

I load my 6.8 mags to the hilt

Not a problem

Dakota was talking about putting 6.8 rounds into 5.56 mags. Some alternative AR chambering can use standard 5.56 mags no problem, but 6.8 only kinda works. That's what he's referring to.

 

[TimW77]

"The 6.5 Grendel is a great round but its designed more for accuracy from longer barrels...

As usual, total BS about the 6.5 Grendel from a non knowing uninformed 6.8 "fanboy"!

As said over and over...

Barrel length itself does NOT change accuracy...

The Grendel is extremely accurate in a 16", 28" or any in between length.

AND, the Grendel does NOT need a long barrel to attain its velocity advantage.

Given similar barrel lengths and bullet weights, the muzzle velocities and at 100 yards are not that different.

"...and high-capacity magazines either nave significantly fewer rounds..."

That is, to be nice, just silly...

In the same size magazine, there might be a 1 round difference between the 6.8 and 6.5 magazines...


"...or don't fit standard mag pouches."

Again, total nonsense, in order to fit in an AR-15 both the 6.8 and 6.5 magazines have to have the SAME OUTSIDE dimensions. If they are the same size on the outside they will fit in the SAME standard mag pouches.

T.