I also have the marlin 336, and have deer hunted with it for the past 3 years. Definately use the 170gr. I use the 170gr remington corelokt and dropped two deer in their tracks at about 30 and75 yards. My dad has an older marlin, a glenfield model 30. Last season he dropped a buck in its tracks at a little over 200 yards with a170gr corelokt bullet. Its a really good bullet for deer hunting.