What kind of choke do you have??? Depending on you choke type will tell you what will fly out of it. One of my shotguns is an 870 Rem. with an 26" improved cylinder, it doesn' t hold a pattern past 25 yrds very well at all, but I can shoot slugs out of it and hit a 6 inch target all day long, ( if my shoulder could hold up ) and that is just with open sights. Now my mossberg is full choke and I use this one for my turkey gun because in being a full choke it will hold a tighter pattern at a further distance. I would say with 00 buck, a full choke will reach out and drop a deer out to 60-70 yrds.
The best way to find out is set up a large target and see what kind of pattern your gun has at various yardages. Good Luck, Bobby