Nothing wrong with shooting hard cast bullets, nothing at all.
Just don't get carried away with the powder charge, stick to the loads listed in reloading manuals for your bullet and you'll be ok.
If you want to softer bullets, go to a scrap yard and buy some lead. Normally it will be soft.
If you'll look at reloading manuals, what determines pressure is the amount of the bullet that touches the barrel. Also you'll notice for the same type of bullet, one being jacketed one being lead, they recommend less powder for lead. I think the soft lead creats more drag.
But, if you'll stick to the loads listed (not max loads) you'll be OK.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071