You can buy different caliber uppers, 9mm, 45, .22, any pistol caliber would be fine on your lower, though it does require a mag block to make the smaller mags fit in the magwell. I don't think .308 works simply because of the length of the cartridge. It would be longer then the standard AR magwell, so the magazines wouldn't work with a normal lower. I'm not sure if the upper is longer as well, so I don't know if it would even fit on a standard lower.BCurry1 said:I have done alot of research (read: surfing the internet) on the AR - 15's over the last two months. I am wondering, if I buy an AR in .223, can I then buy a .308 or a 9mm upper put on it, or do I have to have a .308 lower?
Also, Rock River Arms calls their rifles LAR - 15's, what does the "L" stand for?
Thanks for your help!
There are several alternative calibers that do work though. 6.5 Grendel, .50 beowulf, and .458 socom come to mind. These are designed to fit in the same length as .223/5.56. Usually they are a bit wider, so you lose magazine capacity. The .458 and the .50 make your standard mags a single stack one. Of course, ammo is quite a bit more expensive for these relatively new and uncommon rounds. There isn't any surplus out there either.
There is also a company, MGI, that is making AR lowers with interchangeable magwells to accomplish what your looking for. It's a relatively new concept and I don't know the cost, but maybe it would work for you here is an ar15.com thread about it.
As to what the "L" stands for, I don't know that, they couldn't call it an AR because it is/was specifically banned in the AWB and I think it is a Colt trademark.
I assume you've come across http://ar15.com, but if not, that's the definitive AR resource on the net.
Mike