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mjohns930

AR Lower Receiver Question

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I have a question regarding AR style lower receivers. If someone were to buy one that was marked for 5.56 or .223 or whatever, is that the only caliber upper you are legally able to put on there or does it not matter? I see people selling multi-caliber marked lowers for a premium over the standard .223/5.56 lowers and I am just wondering if it really matters.

So for example, if I had a lower the was marked for .223, could I stick a 6.5 Grendel upper on that and would it matter? Also are the lowers different for different calibers? I am most certain that the lowers for say a .308 are different sized than a .223 lower but what about 6.8spc and 6.5 Grendel?

I have done some searching on this and I can't come up with the clear cut answers I am seeking. I also read over this thread http://www.brianenos.com/forums/index.php?showtopic=78810 but it didn't shed too much light for me on the subject.

Thanks for any help on this.

Mitch

Edited by mjohns930

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lmccrock   

Apparently there is some legal reason to mark the caliber on the lower, but there is no US Federal requirement, and none of the states I have lived in require it. Other states? I guess.

The 6.8spc and 6.5 Grendel fit on AR15 lowers. 308 is a different lower. There is also a Cobb Mfg 30-06 rifle which had a bigger lower, but these are uncommon.

Lee

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gose   
Apparently there is some legal reason to mark the caliber on the lower, but there is no US Federal requirement, and none of the states I have lived in require it. Other states? I guess.

The 6.8spc and 6.5 Grendel fit on AR15 lowers. 308 is a different lower. There is also a Cobb Mfg 30-06 rifle which had a bigger lower, but these are uncommon.

Lee

A .22 AR can't be an "Assault Weapon" here in California, so some people get a little fuzzier and warmer by buying a lower that says multi, or even .22, over one that says 5.56, for their .22 upper.

From a legal standpoint, it doesn't matter at all though.

Edited by gose

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Carlos   

I think that some guys who make their ARs into Class III (actually Title II under NFA) guns - such as "short barrelled rifles" are supposed to have a caliber designation.

But ordinary ARs most of us buy at the gunshop and own? Use whichever upper you like without regard to what caliber is listed on the receiver.

I made an AR lower at home for my own use. It has no caliber listed at all. It also lacked any serial number for a long time too - and it was and is 100% legal. Its all approved of by the BATFE & its listed on their FAQ.

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J-Ho   

Mine says "Multi" for the caliber. I'm still looking for the Multi caliber rounds at the gun shop. ;)

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davidwiz   

The magwell on a AR is different for .223 and .308 (among other things). A .223/5.56 AR lower can handle a variety of calibers, from 9x19mm (with mag adapter), .223, 6.8 SPC, Grendel, etc. while a .308 AR lower can handle almost any "short action" .308 based round, such as the 7-08, .260 Remington (aka 6.5-08), etc. - as long as the round can fit in the magazine.

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Wakal   

The ATF admitted...in writing...that my short barrel rifle AR15 receiver can "wear" any caliber and any barrel length, as long as I maintain at least one short barrel dedicated to the gun. The receiver is marked .223, but the associated paperwork has a laundry list of calibers :)

There is no reason to charge any more for "caliber: multi;" it doesn't cost any more to produce. My "DI" lowers are all caliber: multi and the engraving cost between that and caliber: 5.56 is the same (laughs)

Alex

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