Ok then, a 100% machined stripped lower. The way you phrased the question I wanted you to clear that up.
I agree with the others, if you're handy with tools and want to save a little money, sure - build up a lower with the parts you want - but choose parts of quality.
If you choose wisely you'll assemble a better quality lower for about the same money as a fully assembled entry level factory job.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek