I have a DPMS and the receiver height is normal. I have a 4 rail gas block that is lower than the receiver height. I have no problem with my irons matching up when attached to the gas block. My front sight is designed to go on the gas block and is the correct height. It does take a taller front sight but it is pretty much standardized. The lgs even had them in stock.
"I would not be an old man if I had not been an armed young man." JTJ
Patron Member NRA
"If you have always believed that everyone should play by the same rules and be judged by the same standards, that would have gotten you labeled as a radical 60 years ago, a liberal 30 years ago and a racist today"