Agreed. Rub a little M.A.N. on it, and the pain will go away.

In all seriousness, the recoil IS different because of the weight of the bolt going rearward, then forward with force. Also, with wooden stocks, and synthetic full length stocks, the buttstock DOEs divert energy differently than an AR, which has no such deadening material from stem to stern. But seriously; it's nothing to run 500 rounds and not have a sore shoulder.

The doctors' remedy for AR15 pain? A prescription of 3" 12ga. mag goose loads of 1-5/8oz tungsten. Shoot 20, and call me in the morning.