BTT.
I would say it fits like a medium lol. I typically need a large jacket to prevent my shoulder movement from being restricted on a draw cycle, especially with layers. I'm 5'10", ~155-160lbs., 30-31" waist, and with a ~36" sleeve length. When used in my preferred layering position, as a mid-layer, the medium fits me well. I just have more than a few other vests...How does that medium fit? Like a large? I have very broad shoulders and a small waist.