i bought a rifle kit and a lower from american spirit arms back in 1993.. or 1994.. and built it.. the rifle always functioned flawlessly.

few months ago.. i got a DD omega rail, and i noticed that the rail height did not match my upper rail... i thought it was strange.. so i tried the DD on two Rock river uppers, and they matched perfectly.. so i tried another brand, sundevil upper(sundevil has crappy product and customer service in my opinion) and again it fit perfectly.. so i ended up putting the rail on a rock river rifle i built...

i contacted American Spirit arms and asked them if they at any time built A3 upper out side of mil-spec height.. they told me that they have not..  so i have no idea why my upper is rail is higher than my other rifles..

anyone experience anything similar?  this is the ONLY receiver that is out of spec.. and i only have one american spirit upper, so difficult for me to see if it is just a fluke...

thanks.