I guess I didn't know double-base smokeless rifle powders weren't "modern". Double-base smokeless propellants remain nitrocellulose and nitroglycerine as they've been for 123 years and are just as modern as they ever were. There were no loading problems with it at all. It was simply cut to length and dropped in the case before the case was tapered and necked. It was designed for mass production of munitions, not for handloading.