Hey guys...I can confirm that the Bushmaster ACR is indeed built in Windham, ME. I'll be up there next week to go through the factory and am taking a special guest through to build his own personal ACR. More on that next week.
The marking on the Remington ACR upper actually reads "Elizabethtown, KY" which is where the early Remington samples were produced. Ilion, NY is the permanent manufacturing plant for the Remington ACR long term.
Can't make any promises on bringing out the alternate material lower on the Commercial side, but if it is of interest to you let me know.