Well Colt did make a Sporter in this caliber but I'm not sure what pin size for the pivot and breakdown holes. (Colt's aren't always standard size, thus my concern whether this will work with just any old lower.)
I found a video on the Sporter and it does appear to have standard size holes but he'll have to measure before buying anything yet.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek