I've just replaced the factory rear sight on my BC with the FP sight that H&R sells and I thought I'd post some info. Maybe this has already been posted somewhere but here it is. Hope this will help others who are new to the Buffalo Classic.
The factory rear sight can adjust approx. from 1.000 inches to 1.100 inches above bore centerline.
The FP goes approx. from .935 inches to 1.435 inches above bore centerline.
Practically this means if you can't get your group to zero because you've run out of adjustment on the factory rear sight and you replace it with the FP sight, you'll be able to lower your point of impact by 7.5 additional inches or raise it by almost 39 additional inches beyond what the factory sight will give you. This is at 100 yards. To get even more elevation with the FP you'd have to get a shorter front sight.
Just FWIW