Stock fit can be a big deal too, as far as felt recoil. Like was said above, to compare recoil, you'd have to compare the same gun in each caliber. So M1 Garand vs M1a, or Rem 700 in .308 and .30-06. But comparing a lightweight bolt action .30-06 in an ill-fitting stock and no recoil pad to a bull barreled AR style .308 would not be fair.