I would shoot it with the open sights first and see how it groups. Start out close and work back to 50 yards. You will be surprised at how accurate the open fiber optic sights are.

I did mount a scope on my Black Diamond XR. I put low riding weaver style mounts and a set of Quick-ee rings. The scope I picked was a 1.5 X 4.5 32mm Bushnell Banner Dusk to Dawn Shotgun scope with extended eye relief. The scope was under $70.00. I find the scope very clear and excellent for the money spent.

The reason I went with a low mount scope and not a see through is, you will find that when people put a scope on their rifles they very seldom ever again use the sites. Also the lower mounted scopes are more comfortable to the shooter and the shooter is far better able to get into the same sight position on the rifle time and time again.

The reason I went with the low end scope is, I wanted to keep the cost down, but I was very impressed with the quality of the scope. With the scope on the low setting of 1.5 power I get a excellent field of view for close range shooting. With the scope on 4.5 power I feel it is more then enough maganification to make a 100 or even 150 yard shot. I would seldom ever get a shot more then 60 yards, so this scope will work perfect. I shot it today in the snow and cold and it worked perfect as usual.

The nice thing knowing your sights are on is, if your scope is not hitting and acting up and your not sure it is the load your shooting or the scope, pull the scope and shoot the load with the known open sights. In fact I worked two loads up with the open sights before I scoped the rifle. I have even thought about taking the scope off because we can not use them during out muzzleloader season, but I have six other rifles to choose from, so the scope will stay...

Another good scope and still low dollar end which is an excellent value is the Millet Buck series.... I believe it is a 3 X 9 power. There are other choices in the Buck series. Just do a search and check them out. I almost spent the extra and went with that scope, but Bass Pro had a sale on the Banner at the time, so I took the deal......