AR lower receiver

[metalman8600]

I am new to ARs, but I like how it is somewhat modular in that you can get a longer/shorter barrel and easily put it in just by changing the upper.

Do .308 ARs and 5.56 ARs use the same lower receiver?

 

[Acera]

No..

 

[metalman8600]

What about 5.45x39 and 5.56x45... same receiver?

and 7.62x39 and 5.56x45? I am assuming no on this because of the no on the .308

 

[hatchetbearer]

5.56, 5.45, 7.62x39, 9mm, .458 SOCOM, .45, 6.8 SPC, 6.5 Grendel, .50 beowulf, and most likely a handful of others can all go on the same lower, using different upper receivers, bolts and magazines. you can even mount a .50 BMG upper, but it is side magazine fed or single shot, depending who you buy it from. I have also seen a cross bow upper for that tactical ninja.

 

[Tirod]

It has to do with the magazine well length. If you can hold the overall length under a certain dimension, about 2.600", they can make a magazine and it will fit the AR15.

The 6.8 and 6.5 are a good comparison. The 6.8 has a 43mm case and a shorter bullet, the 6.5 is 41mm (?) and has a correspondingly longer bullet. The fact they both fit the magazine well is about all they share. They don't stack the same, use different magazines, have much different ballistics, use optimum barrel lengths that are 6" different.

The lower doesn't care, and have the same operating and handling characteristics is nice. Use a 5.56 for three gun and plinking, a 6.5 for long distance precision, and a 6.8 for hunting. Jordan is getting licenses to build an 8" barreled 6.8 Personal Defense Weapon for their security forces.

For the casual shooter, it makes for a more versatile gun case to have different uppers and familiar handling.

 

[Darthbauer]

And if you go with a 5.45 upper you can use the same mags as the 5.56

 

[migkillertwo]

I am new to ARs, but I like how it is somewhat modular in that you can get a longer/shorter barrel and easily put it in just by changing the upper.

Do .308 ARs and 5.56 ARs use the same lower receiver?

welcome to the world of AR-15s

No they do not use the same lower receiver. However 5.56 AR lowers accept 6.8 magazines.

Anyway, if you're looking for a 5.56 AR lower receiver and you're on a budget, I'd recommend the DSArms ZM-4 complete lower receiver. I have one and it works just fine. Has never failed me yet.

If you're looking to get a .308 AR-15, don't build one yourself. The parts are not as standardized between different manufacturers as the 5.56 parts. Either get a DPMS .308 or a Rock River Arms .308.

 

[Acera]

I am assuming no on this because of the no on the .308

You only asked one question in your original post, and that was the simple answer.

 

[Tirod]

Consider the AR15 the short action, and the AR10 the long action. It actually came first, was produced first, and chambered in the bigger NATO caliber first. It has about a 1 1/2" longer lower and upper, longer bolt, longer charging handle, and about 2 more pounds. While I haven't seen one in .30-06, it can be had in those sized rounds, vs. the shorter intermediate loads.

No doubt to come for those with enough money, the AR XX length in magnum calibers. Reading human nature (more accurate than a crystal ball,) there will be a .338 Lapua AR someday.