To answer your question, yes a 50-55gr factory load will work best in your 1/12 twist rifle. 1/12 & 1/14 is fairly "standard" for the various 22 calibre centerfires and 40-55 grain bullets are the normal fodder except for the folks shooting heavier milsup ammo or trying to duplicate military specs in which case a "faster" twist is called for, ie 1/9 or so.