We have coated AR, AUG, and AK, HK plastic with never any problems whatsoever, even some of the really cheap butler creek stocks for hunting rifles. The stencils are $80 each and with that you get your choice of up to four 4oz bottles of Arma-Coat for $12.00 a piece. (Regular MSRP is $17.99 for 4oz's) The stencils are reusable and can be baked up to 350F. With this stencil kit and up to 16oz of Arma-Coat you can finish about 8 M4's if you use the product effeciently.
www.armacoat.net