Shot many a flat base 139 myself, very accurate and solid reputation of clean kills, tad more accurate than the boatail in my experience and a few cents cheaper.
FWIW, it's what Rem loaded in their initial '140 corelokt' loads for years over a powder like W760/H414...48-49gr comes to mind, but check it. Me - I loved Varget and IMR4064.
I killed deer w/120s in SP and HP Hornady's via a 7mmBR rifle, at 2878mv, but prefer 140s typically.
