I use a kicks turkey choke and remington express high velocity 3" # 4 buckshot in my 870 express magnum. I bought these shells at sportsmans guide for $3.00 or so for 5 . this was the best price I could find they are buffered and pattern great in my gun. As far as range no one can tell you . You'll need to pattern your own gun. I have taken coyotes out to about 55 yards which is my max . Try several different loads to see which patterns best in your gun then do a search and you may find them cheaper as I did. #4 is the best size shot I've found for coyotes , bobcats . You still get a good size pattern with minimal pelt damage as long as you don't shoot them when there in your lap, let them get out at least 20yds. or more with a xtra full choke if you care about hides.
Good - Luck,
zapper :-D