I have pretty much decided I am going to add a 450 bushmaster upper to my shrinking gun collection. I have read pretty much everything on it I can find. The only thing I am struggling with is 16 or 20 inch. I had to write everything down in order to really figure out why I couldn't make up my mind. Figured out that the only reason I prefer the 20 is it will have less recoil. I plan on applying all the other tricks to reduce the felt recoil. Just how much difference is there in the felt recoil between the two? Thanks in advance. Chris