Congratulation with your new/old gun

I would advise you to reload ammo in blackpowder. The original load for the .500BPE was 140 grain Black powder + 440 grain leadbullet. I don`t know if the germans had some other loads aswell??.

If you are going to shoot this thing as you intend, it would be adviseable to have your barrels "slugged", and then order a bulletmold for the nominal dia.

Midway has a lot of reloading stuff, but also Buffalo Arms ifn idaho could supply you with stuff, such as brass , dies and bulletmold...maybe ever good leadbullets aswell.

The .500BPE caliber was considered a large medium bore of its time, and practicly every gunmaker around the world made that caliber.

IF you are going to reload smokeless powder, I would have the gun checked by a gunsmith WHO KNOWS SOMETHING ABOUT DOUBLERIFLE AND BLACKPOWDERLOADS....not just any local "bubba"...even if it requires some travelling out of state.

If your gun is tight you shouldn`t be affraid to makeup blackpowderloads with FG/FFG blackpowder.
There are many books about reloading blackpowder rifle catridges...techniqes and such....one cannot too much litteratur about ones favorite hobby...bookcollecting will become a secondary hobby..hahaha

Never feel you ask too much....much better to ask too much...hahaha.
Please bring a picture!!
Everybody here loves to watch pictures