Dopey AR question

[brewer12345]

I bought a complete lower and complete upper, both made by Aero in 556. I actually have yet to put them together, but the lego set nature of these things makes me curious: if I wanted to shoot other calibers, do I just need additional uppers (and mag)? Is there a limitation on what caliber upper I can slap on my lower?

 

[Panzerschwein]

Not if it's made for a standard lower... which is most things. Sometimes, all you need is a new barrel for shooting something like .300 BLK.

 

[Jackal]

There are a number of other calibers that will work. Some require only a barrel swap, others need barrel, bolt and mags.

 

[OilyPablo]

Depends on caliber. My 6.8 upper works fine with my 5.56 lower, just gotta use 6.8 magazines and 6.8 bolt. Always need bolt match. My 10mm AR is all alone. For example.

 

[1911 guy]

Everything they have posted is correct, but let me add details that might clear it up for you.

The limiting factor for you right now is magazine length. That's why the AR10 (.308 caliber) is a separate design. But there are plenty of calibers that fit into the magazine length (or less) of 5.56x45mm.

Everything from .22 rimfire up to .450 bushmaster will fit in the magazine well of the standard AR15 lower receiver. However, bolts and magazines are a mash-up. Some cartridges were designed from the ground up to use both existing magazines and bolts. Others use the same magazine but require a different bolt, while a few require magazines and bolts all their own. But all will fit into the AR15 lower receiver.

New stuff all the time, but there's something like two dozen calibers to choose from if you want to switch things up. Some are cartridges that previously existed and uppers made to fire them, while many are cartridges designed specifically for the AR.

 

[OilyPablo]

And people still wonder why AR-15 is popular? Pretty funny really.

 

[DIY-Pete]

Top expand the OP's question. Would I be correct in saying that if I had an AR set up for 5.56 and wanted to go to 300 blackout I could just switch uppers and use the same bolt carrier group, but if I went to .458 SOCOM I would have to switch the upper and the bolt carrier group?

Pete

 

[bangswitch]

Top expand the OP's question. Would I be correct in saying that if I had an AR set up for 5.56 and wanted to go to 300 blackout I could just switch uppers and use the same bolt carrier group, but if I went to .458 SOCOM I would have to switch the upper and the bolt carrier group?

Pete

Yes.

.300BLK uses the same upper, same BCG, same magazines as .556/.223. Only difference is the barrel. Bolt and carrier are the same, because the .300BLK case is made from .223/.556 cases, so the case head is the same size.

6.5 Grendel only requires a barrel and a different bolt, but uses same carrier, and the magazine is slightly different (follower) I believe 6.8 SPC is about the same.

.458 SOCOM cases are much larger diameter, but only the barrel and bolt are caliber specific. The 30 round magazine becomes a single stack and holds ten rounds.

You might want to check out the .50 Beowulf, too.

 

[DIY-Pete]

Thanks bangswitch

 

[W.E.G.]

...and while you CAN switch to all these adapted calibers, at the end of the day, you are probably looking for more power.

Appreciably more.

In which case you will need to upgrade the whole thing to take .308
Lotta people complain about the 5.56 being not enough gun.
You'll have to look hard to find anybody who will argue that .308 is not enough gun.

The 5.56 in other calibers is handy if you want to play around with adapted "niche" calibers. The .300 BO is popular with people who want to shoot heavy bullets real slow. In my opinion, none of the other caliber options on the small receiver offer enough extra-anything to warrant the distraction and cost.

You can get a complete .308 AR for what you will invest in getting a working AR upper on the small receiver in .458 or .500 caliber.

 

[1911 guy]

I seriously love me some M80 ball. But the size and weight difference in AR15 and AR10 receivers is noticeable. Plus, the other calibers are "niche" calibers, in that they fill a specific role between the 5.56 and 7.62.

When you need a .308, nothing else will do. But sometimes we shoot niche calibers simply because they'll do for our purpose and we're intrigued by them. And sometimes we shoot them just because they're cool.

 

[W.E.G.]

I've been down the "cool caliber" path.

Nothing wrong with it if it entertains you.
That's what hobby gun ownership is all about.

But, for utility, "boring old 7.62 NATO" AR weighs a lot less than you might think.





Accurate. 100 yards.
Not using "ball ammo" though.
This was with Lake City M852 (which is basically 41.5 grains IMR4895 and a 168 SMK)

 

[gojuice101]

You can get a complete .308 AR for what you will invest in getting a working AR upper on the small receiver in .458 or .500 caliber.

I have to disagree. The cheapest AR-10s I have seen are over a grand (unless I'm missing some super cheap ones somewhere). I built my .458 SOCOM for less than half that.

 

[brewer12345]

Frankly I bought the AR because they are currently pretty cheap and there is potentially elevated risk of political restrictions on ownership thereof. I don't really have a use for a 5.56 rifle, other than as a range toy. I can't legally hunt deer with it in my state. If I use it for small game (which is perfectly legal in my state) it will mean my quarry is splattered across the landscape. My go to for home defense is a revolver or a shotgun. Hence my question.

Realistically, the only calibers I would be interested as add-ons would be .22LR or WMR, or something sufficiently powerful such that it is at least .23 caliber and produces a minimum of 1000 ft.-lbs. at 100 yards.

 

[1911 guy]

Here's a list of calibers you can convert to:

https://en.wikipedia.org/wiki/List_of_AR_platform_calibers

 

[12Bravo20]

Frankly I bought the AR because they are currently pretty cheap and there is potentially elevated risk of political restrictions on ownership thereof. I don't really have a use for a 5.56 rifle, other than as a range toy. I can't legally hunt deer with it in my state. If I use it for small game (which is perfectly legal in my state) it will mean my quarry is splattered across the landscape. My go to for home defense is a revolver or a shotgun. Hence my question.

Realistically, the only calibers I would be interested as add-ons would be .22LR or WMR, or something sufficiently powerful such that it is at least .23 caliber and produces a minimum of 1000 ft.-lbs. at 100 yards.

Sounds like you might want two different uppers then. Look into a 22lr upper for small game. If you want to hunt deer, look into either a 300 or 6.8 upper. I personally like the 6.8 for deer.

 

[USAF_Vet]

You can get a complete .308 AR for what you will invest in getting a working AR upper on the small receiver in .458 or .500 caliber.

I don't know about all that. I've got links to .450 Bushmaster upper kits (granted, not .458 SOCOM or .50 Beowulf, but certainly on that level) for as little as $550.

The absolute bottom dollar for a .308 AR is near double that.

 

[J_McLeod]

Yes.

.300BLK uses the same upper, same BCG, same magazines as .556/.223. Only difference is the barrel. Bolt and carrier are the same, because the .300BLK case is made from .223/.556 cases, so the case head is the same size.

Would there be anything wrong with using the same bolt in two uppers, one for .223 and one for .300 BLK?

 

[USAF_Vet]

Would there be anything wrong with using the same bolt in two uppers, one for .223 and one for .300 BLK?

The only thing wrong is different bolt wear patterns on two different barrel extensions. While it's probably, nothing to worry about, I prefer to have a dedicated both for each barrel. Although, I have installed a brand new bolt into a used gun, and swapped that used bolt into a new gun. The used bolt and barrel were at a fairly low round count, though.