This one gives me a semi-
http://www.gunblast.com/50Beowulf.htm
A .50 cal AR! ! ! ! ! ! ! ! !
Yea that's a bad ass weapon. It's interesting that it can use a 7.62x39 bolt. That's a good thing because if you ream much more metal you start to have breakage problems. Others, like Bushmaster are making .48 - .50 cal offerings as well. You WILL learn a lot about handloading if you shoot these rounds.
Alexander Arms is an interesting company. They make first rate weapons and are very innovative. That said, IMHO their proprietary marketing practice of requiring other companies to pay licensing fees to build anything around their rounds has really hurt the growth of their products.
The 6.5 Grendel is a great example. A few years ago there was a real dog fight between the 6.8 SPC and the 6.5 Grendel. Both fantastic improvements to the AR platform. The 6.8 SPC is a little better at short to med range and the 6.5 is a little better at med to long range but basically a dead head as far as performance goes.
Fast forward 3-4 years and every major manufacturer of ARs (except Colt LOL) makes at least one 6.8 SPC weapon. Most offer it in every style weapon they make. Ammo is being made by several major companies and bullet makers are begining to offer more and more choices for 6.8 SPC.
Equate what's happened to the IT world.
The 6.8 SPC is an "open systems" offering like Linux. The Alexander Arms 6.5 Grendel is proprietary. Over the years many small companies and creative individuals have worked together to improve the 6.8 SPC. Most of the major innovations allowing drastic improvement in performance, like an improved chamber and barrels using the proper twist rate, have come from individuals. Individuals that would never be able to pay Alexander Arms a royality. These innovations were picked up by the weapons makers and are now available to everyone.
The 6.8 SPC is considered by most to be mainstream now. The 6.5 Grendel, a fantastic perfomer, is still not much more than an interesting wildcat.