Quote Originally Posted by CBR View Post
Heavy arrows would be about 100-110 grams max and velocity 55-40 m/s depending on range and bow. That is similar if not less momentum than from a baseball thrown by some major league pitcher. Now I have no experience in being hit by neither a baseball nor an arrow but FWIW I'd say as long as the arrow didn't penetrate and the target was not scared by the sound of impact he would be fine.
Getting hit by a baseball by a major league pitcher hurts. A blow to an unprotected head (if the pitcher was hurling their best stuff) could easily kill you. I would think that your helmet would be knocked back and it would make a nice sound, if it didn't penetrate.