Thanks for the info.
I was reading how heavy or medium profile barrels may be too heavy. I got a reply from Lothar and the barrels are 740 before the gas block and 850 after. I could also have it lathed down to cut weight.
I found a different upper with a DPMS 18" ss 1/8 barrel with rifle gas, yankee hill 5009 free float, flash hider, lo pro gas block. I like the idea of a rifle gas upper too. BCG and charging handle. I could always add a small rail to the button instead of having all the rails add weight and grabbing on everything. This one is only $625 minus $20 shipping.