I want a 10.5" barrel gas piston upper for my soon to be registered SBR Rock River lower. My friend has a HK 416 upper and it is unbelievable, he hasn't cleaned it in about year and it is still spotless inside after about 1000 rounds. I was checking out LWRC, but the back order is ridiculous and I heard that POF uppers aren't very good.

My question:
Bushmaster sells a gas piston conversion kit for a carbine length AR ($399), and I was wondering if anyone has ever installed one? and how is the quality?