If it is dangerous to fire the new ammo in the 88 rifles, the Germans didn't know it since they issued them to reserve units along with the "S" size ammo.
Oh, I'm sure they knew it ..... they just did not think ther reservists would fire it enough to matter ...... or they did not care. The Turks certainly did not.
I can tell you that 50K CUP loads in an 88/05 WILL do bad things to the recieviever, and fairly quickly.
I can also tell you that a short barrelled 88 carbine will not develop enough pressure to obturate with the max loads listed for the 88 in most manuals.