User Review: Big Agnes Lost Ranger 15°
Fill: 650 down
Temperature Rating: putatively 15 degrees F
Very comfortable sleeping bag. I like not rolling off the pad.
I used it in the Adirondacks on a cold Columbus Day weekend (temps in the low 20's) along with a lightweight down sleeping bag liner from Western Mountaineering. I tend to sleep pretty warm, and with the liner I slept very (but not overly) warm; bottom line, even for a warm sleeper like me, I am not sure about the 15 degree rating...
One thing to note about the Big Agnes system: I was using the bag in a lean-to. Because the pad slips right into a sleeve on the bottom of the bag, it was a bit more of a pain the butt to roll it up in the morning, so I didn't. That turned out to be a little unfortunate when the snow blew straight sideways into the lean-to -- I came back to find a fair amount of snow on the bag.
Moral of the story -- be less lazy than I was, or throw the bag/pad combo in the back of a lean-to along the rear wall.