All depends on your gun and choke. Also different brands shoot differently. You should have patterned your gun weeks or months ago. But as joeturse said you should be good to 50 yds. However I noticed you mentioned slugs, if you intend to shoot 00 through your slug gun let me tell you the rifling in the barrel will ruin the pattern. If you are shooting out of a rifled choke tube you are good out to maybe 20 yds. And shouldn't even be thought of, in a fully rifled barrel. How ever if you are shooting through a choke tube just go and buy one that works. If you don't have time to pattern it than I recomend a modified. It will always work. A full choke is better. But on some guns, and brands of buck shot, It might constrict the pattern too much, so when they come out of the muzzle they are actually fighting each other and and flare out, But with the new plastic wads it seldom happens.