I give one a bit of a try.( it was borrowed and had to give it back) I only tried it on The bulk stuff of various brands . It looks like to me it improved accuracy a small amount in almost every case. What ammo was working best before the die also worked best after. My buddy (die owner) said it turns the shallow hollow pointed federals into terrific gopher killers if you put a good hollow point on them. Conclusion - if you need better ammo , buy better ammo . That said ,its a great toy to play around with. Like another buddy used to say, more toys makes us shoot more, and that makes us better shots.