I haven't shot the long rifle, but I can attest that Nazi 1938 ammo is brutal from the carbines! I chronographed and it's plenty hot for that old of a rifle and cartridge. The 8x56R is a very underated round. If you think about it and you have one that has a fat groove, you are very close to it being a 338 then a 323 groove for a 8x57. That's an impressive round.
I use to shoot wheelweight alloy and 50-50 alloy from mine and I shot the fattest bullets that would chamber. It shot cast exceptionally well. I did have to put a higher front sight on my carbine as it shot extremely high at 100 yards.
So if you fellows thing the long rifles can be unpleasant with that original ammo try shooting the carbine!!