Did you actually sell it without even trying it? Were you aware of the massively weighted buttstock, as explained by Shell Shucker above? Taking that out transformed that gun, making it a very easy carry; a real compact powerhouse.
OP, you should also consider trying one of the other H&R slug guns if you can locate one of them. The Ultra was made with a 10-gauge barrel blank bored out to 12-gauge, so it had extremely thick and heavy barrel walls. The other H&R slug shooter, I think it was called the Tracker, had a standard-weight barrel and open sights. I never tried one, so can't comment on its relative accuracy.