ORIGINAL: Briman
Doesn't DPMS make an AR-15 based .243?
It would be an AR-10. A .308 case will fit in a AR-15 magazine with about 1/4" to spare,the AR-15 just isn't long enough for a .308 parent case.
Sure looks like an AR15 to me.
http://www.dpmsinc.com/store/products/?prod=1998