A marlin with JC Higgins model 45 on the barrel. Not Microgroove and pretty clean mostly.Picking it up tomorrow so will get a closer look at it then. I guess I will use the 182 grain NOE mold I picked up a while back and probably load it to 1900 fps for my grandson to use this year. What is the best powder for this speed in the 20 inch barrel? Blue Dot?