I have my 1919 set up to run 8mm. If you're throwing volume you need cheap ammo. I have cases of milsurp.
You can buy by the pallet at classic firearms. During the ammo panic surplus 8mm wasn't bringing in huge money. Probably cause a lot of us 8mm people stacked big surplus ammo.
How does it run? My a4 is running '06 and the a6 is 7.62 NATO. It's a conversion by the IDF. The MG34&42 are both 8mm.
Some people will 1x fired buy berdan 8mm brass. The good thing about berdan in the US is you know it's only once fired.