Antlers - For the simple reason that I can eliminate one more step from the loading process, I avoid using fillers. I also use H4831 wherever I can. It fills the large NE cases well and using one powder is just another step towards simplifying my reloading chores.

All of the new 450/400s I've loaded for have shot to regulation somewhere between 79 and 82 grains of H4831. In the 26” barrels of the HEYM, 2080-2100 is the average velocity I expect to see with those loads. The bullet you use will have some impact on that charge, as will the obvious altitude and temperature variables that affect powder burn and pressure.

Having said that, common sense rules still apply; back off an appropriate amount and work up each load gradually. Powders can and do vary from lot to lot, and a specified charge will not necessarily guarantee you the same results. If you don’t have a chronograph, you should. It is a very insightful tool to use when developing loads.