If you have the ammo, clean your gun real good, shoot one any where by the target(called a fouling shot) and THEN try a couple of different size bullets of a minimum of 3 shot groups and see which shoots the best at 100 yards. To be fair, have a target for each size bullet and shoot a 150 in the first, then 165 in the second and a 180 in the third. Repeat minimum 3 times in that order. This will help eliminate, flinches, sneezing, hiccups, irregular heart beats, fatigue, buck fever, two legged buck fever watching you or shooting next to you and prejudice of different ammo. Over the years I've shot 150s, 165s and 180s. I keep coming back to the 165 grain, mostly because it is a tact driver in my gun.