My first concern with themwould be lead fouling. Since they have no sabot to protect the projectile I would be sure to give your barrel a good cleaning afterwards.

Second, Remington themselves advertises to expect 3 in groups vs copper solids at 2.5 in and core lokts at 1.8 in.

The one thing that does intrigue me though is that they are full bore slugs. That means that theoretically they should perform best in guns with a relatively slow twist rate of 1-35 or 1-36. That should perform well in guns like my Savage 210 or a Mossberg 695. Not sure if it would have I'll effect on guns with a faster twist such as your H and R which I believe is 1-28, and ideally suited to sub-caliber projectiles.