ar15 lower and upper compatibility

[Furr_Shizzle]

Hi i'm fairly new to the ar-15 scene and i've been reading for the last 3 or 4weeks. I was thinking about buying a 5.56mm lower receiver and using a 6.8 upper. As i recall people say the lowers are interchangeable and the only thing you need to change is the bolt, barrel, and magazine. But I get confused when certain websites sell lowers that specifically say 6.8 or 7.62x39mm or 5.56mm and forums say it's interchangeable. I just needed clarification any help is appreciated. and does anyone know of a good 6.8 upper or barrel atleast? thank you.

[tacticalcity]

They are physically compatable. However, it is advisable to make sure the caliber marking on the side of your lower says MULTI rather than a specific caliber. I am 90% sure, but not a 100% sure, its not legal to have a different caliber on the side than the gun is actually chambered in. I remember reading an ATF letter that specifically said this when researching building a 9mm AR PISTOL. The letter was original about the use of various buffer tubes in an AR PISTOL, but the last paragraph specifically said the marking on the side could not be different than the caliber of the gun. A "Multi" marked lower allows you to use any caliber you wish. Bill Wise and a few other legal experts can confirm whether or not that is true, or whether or not some ATF representative got it wrong in a specific letter that was later corrected. If you do some searching, you'll find that letter. I am not trying to spread fud, just passing on what I read off an ATF letter posted on AR15.com.

There are plenty of Califonia Legal lowers (OLL) out there that say MULTI instead of a specific caliber. Mega Machine is a perfect example.

Your 6.8 upper will come with everything you need to make it work except the 6.8 magazine. Best to buy it completely assembled for that reason.

7.62 NATO which companies also pitch as .308 uppers are a completely different animal than 6.8 or 5.56mm. When they say 7.62 will work with a 5.56mm lower, they are not referring to the NATO round, they are referring to the Russian round used in the AK47.

There are lots of places to get a good 6.8 Barrel assembly, completely put together for you. I carry them on my website and have them in stock ready to ship. Other dealers that are members on Calguns.net have them as well.

http://www.tacticalcity.com