I found that the Brenneke KO slugs worked very well, in my 870 (with factory slug barrel). These have an attached red plastic wad....that stabilises the slug in flight, similar to the feathers on a shuttlecock. The Brenneke slugs always produced about 2 -3" groups at 50 yards, for me. I could even get 6 - 7" inch groups at 100 yards....though I had to "hold over" so much, this was inconsistent. I must disagree with those that say that just about any (so-called) rifled slug will give equal accuracy. I tested, in addition to the Brenekes, Remington, Federal and Winchester slugs. No comparison, in my gun. The Brennekes were worlds better.