I have recently tested the winchester, remmington slugger, and the federal truball rifled slugs through my win. 1200 defender, and the federal truball shot the most accurately. The truball is designed to work similarly to how a miniball does so that the slug will expand a little bit to better fit itself to the bore of the gun as it travels through the barrel.
The remmingtons work ok , and the winchester was least accurate for me.