What is the definition of a high power rifle?

Answer 1

A Rifle that exceds 270 grain and larger then .30 calibre A Rifle that exceds 270 grain and larger then .30 calibre

General usage, 30-06 and above. Often includes high velocity .22 like .22-250. The power of a rifle is measured in foot pounds, 1/2 M Vsquared where velocity is feet per second m is mass in pounds. Much larger rifles like .375 H&H mag are usually called big game