I went with a 1-9" on my F-class rifle and it shoots 180 grain bergers great, I have not tried any heavier than that, I am at about 600 feet ASL so no gain from elevation. I just purchased a Brux 7mm blank for a hunting rifle 21-inch barrel and spec'ed a 1-8.5" to be on the safe side and I wanted to be able to shoot monos.
