For anyone looking to reduce fps on the scar/m4, I just posted this on the arnies scar thread/gas guns info.
As for the scar itself, the sound/recoil are amazing. The youtube videos don't do it justice. Hop up needed a little breaking in, but it's more accurate than I had hoped and reinforcing the stock was simple. I just stuck in a small piece of dense balsa wood about 3/4 inch long between the most forward part of the cheek rest and the base plate of the hinge. For the price I couldn't pass it up and I would definitely buy it again.