Well, the elevationmakes a difference. I think the ballistic coefficient goes up about 5% for every 1,000 feet above sea level. Most likely, however, it is a scope height issue. I'm using fairly high rings so I can still leave the open sights on the gun. This can artificially flatten out the trajectory.

I use RWS musket caps. Not sure if you're doing anything "wrong". It is what it is - as long as the grouping is good, hold for whatever drop you are getting. Good luck. Roscoe