+1 on what NoMercy448 said also.
If you have the time, you might want to shoot a few shots at coyote size paper targets different distances so you can pattern your shots and know where your buckshot hits.
When we had the old 870 riot shotguns in police cars with IC chokes, most of the patterns with 00 Buck got too wide after 25 yards (i.e. weren't in the black) on the FBI B27 silhouette target which was an obvious liability issue. When we switched to tighter customized barrels with lengthened forcing cones, we were able to shoot groups with all of the buckshot on the same target at 35-40 yards and most of the buckshot on the target at 50 yards. Here's a link if you're curious about the gunsmithing used on those barrels.
https://vangcomp.com/