I also shoot o/u but in the field it really don't make a heck of a difference. The gun should fit you. In theory, you're not suppose to be looking down the barrel,you're suppose to concentrate on the bird. Once you mount the gun, you should automatically be looking straight down the barrel.

In target shooting, there's alittle more to it because the little clay things are moving much much faster.

But I shoot best with 870 pump because that gun fits me well.