For a cow, its ok. Any less of a bullet at that weight an' speed I' d be worried. You still might git a blowup. A 165 might be the happy medium. I rely on 180 NPs myself. They ain' t failed me yet. I usually git complete penetration. I don' t like finding pieces of my bullet all over. Makes me worry about next time. I say try the 165s. You also don' t need 1/2" accuracy. Chances are, you won' t have field conditions to mimic that level. 1-1/2" accuracy is all you need for the odd 250 yard shot off a pack or down tree. I like my bullets like my wimmin, heavy an' only fast enough to git the job done right.