First, get yourself a chronograph and do not start developing your own loads until you do that. Hot loads are a big no-no with DRs.

Second, start with a lower recommended powder charge that what you were told, and work up from there, shooting over a chronograph.

When you find a combo that works for you, LOAD UP ON THE SAME LOT OF POWDER THAT YOU DEVELOPED WITH!!!!! Because if you change lots, you will probably have to redevelop a new load for that new lot of powder. I've had to do it, and I'm sure a number of guys had to do it too to get the best groupings.

But get a chrono and make sure you are not going hot - that will potentially cause big problems later with the gun.