Are semi autos less powerful than a bolt action?

No, however each action has it design limit and so do you! More cartridges are chambered in bolt guns because its easier and cheaper then developing a auto to work with each cartridge case and load. Remember we have auto loading main tank and artillery pieces (203mm ie 8 inch guns!)

CD

Depends on what your hunting. My targets shoot back! Back in 89' my unit had some Browning BARs in .300 Win Mag with heavy barrels for sniper rifles. Now almost 20 yrs later FN comes out with the FNAR. I have great confidence with my M14 to shoot 1000yds with iron sights shooting 7.62/.308 loads.

CD