A:
Scott,
I don't know about an H&R slug gun and you did not mention the gage, scope or
iron sights. I have a Savage 20 ga. with
a scope and it shoots great , within, 2 inches @ 100yds. You have to use sabot
slugs and they work great. They make range finder scopes for slug guns.
I suggest zeoring it it at 100yds and then
moving the target to 125, 150, etc. No one
can tell you how your particular gun will
shoot. That is up to you to find out.
Good Luck,
Doug