i guess it depends on the use, too. i've got a browning BLR in 270 win that isn't too pleasant to shoot off the bench for extended periods. i get a sore shoulder, no doubt. but in the field, with just the odd shot taken, it's a beauty.i reckon 308/30-06 is the absolute upper limit for a 60-round session, and even then you'd want a reasonably heavy rig. once you pick up a flinch, it is damn hard to get rid of, and your accuracy is gone. a 7mm in the boiler room of most animals will do the job, a 50-cal in the wrong spot will do nothing.i agree with jamesb and ideaman. for practising technique, there is no point shooting cannons. something in 223 or 222 that you can shoot all day with little wear on shooter and barrel makes a lot of sense. and if you really want to hone your "pure shooting" skills, you can't beat .22lr smallbore target competition. trigger control, breathing techniques, sight picture.... all the basics are hammered home without the worry of busting yourself up. but i suspect i've gone way off topic.

the 06 will have less recoil.