I'm trying to do the same to my 870 20ga. I like the 336 since it lets you mount the ff3 directly to it which keeps it sitting low on the receiver. When I got on Burris site I saw a mount specifically for the ff sights. Will it work on an 870? If so, will it keep the sight as low as the 336? Just curious as to why I haven't seen anything on the Burris mount and a lot on the 336.