Depends on the weapon and the blanks. I do a lot of military reenacting. Civil War, WWI, and WWII.
Depending on the weapon and the quality of the blanks you're using, some are very mild. Some (very few) are almost up to live ammo.
Easier to up ammo on bolt guns and muskets.
Wood tip blanks have more kick then crimped rounds in my experience, but you had better be sure you have a good BFA on the end or you'll be sending lots of nasty bits out.
I know the .50 blanks in the Boyes AT rifle kicked pretty good.
Jeff