8x57 is fine and a great round if kept under 150yds or so. Hugely underrated IMHO
It would have been unpleasant because of the rifles stock design most likely, esp. if it was the original k98 stock Sporterised and original steel buttplate. There’s nothing in it recoil wise between the 8mm Mauser and your beloved 7x57 really.
Could also be it was a heavy pill, thy can handle up to around 200g, which gives a fair amount of recoil