The military arrows came in at about 750 grains and were good to about 400 yards. At Crecy they faced knights dressed in chainmail and were very effective.
I shoot large bullets in the 400 to 500 grain range and 750 grains is a very scary number. The projectile just keeps going after hitting the target.
There was a story from Agincourt (or it could have been Crecy) about a french knight that was hit in his leg as he sat on his horse. The arrow punched through his armor, his thigh, the saddle and hit his horse. The horse wheeled around and another arrow hit the knight's other leg and repeated the process. The knight was stapled to his horse by arrows.