Fill weight and temp rating: Western Mountaineering vs. Montbell UL SS

[paul buzzard]

I have the same bag, and for me, its' ultra conservatively rated. I think if you are slim person,and I am, 6' 170#, these bags are as quality as the WM. That is because slim people don't stretch the baffling and deloft the bag, and the SS feature drapes you, reducing the air volume inside. Who knows, thou lol. I slept in a shelter 2 weeks ago for two nights, low was 8 and 11 at 7 am. Used light weight down jacket and vest inside my bag as helpers, slept in wool socks, light poly pants and cotton tshirt, light fleece cap. Warm as toast. Happy flip floppy side sleeper who is very happy with this bag.

[Brad Groves]

Ok, lots of great info here. FWIW, there is no doubt in my mind that greater density of down yields a warmer bag, and I greatly appreciate all the work Richard has done for us.

That said, we're getting far away from the point at hand, IMHO. We're getting all wound up discussing how the MB bag w/less loft could be warmer than the WM bag. In so doing, we're ignoring the basic tenets of density: if the down in the MB bag has less density, ie thin spots, then it would only magnify the effects of a bag with less loft. I think that's what the original posts were about. The MB bags in question had thin spots. Spots where there was very little down between the shells, maybe even none? So we're starting off with the premise that the MB bags have less density of down as well as less loft relative to the WM bags in question. These are traits I see regularly in many manufacturers, and traits that many of us can attribute to other (under) down-filled products we use. It is all about density, and the OP's experience was that the MB didn't have enough density–or so it seems.

Lastly, as much as I hear about Valandre bags, I think I'm going to have to check one out!

[Anonymous]

I have never owned a bag that wasn’t on sale, that is until this year. I have been freezing in a 15° bag that kept me warm when first purchased but now as I approach my mid-60s, find that I am not producing the BTUs that formerly kept me warm with the skimpiest of bags.

Tired of being cold I purchased a 10° WM Versalite at full retail price. Ouch! After all, the 15° bag left me shivering at night. The Versalite has been too warm on all but a few nights. It really is a 10° bag or warmer. Since then I managed to find a WM Megalite on sale and, although a 30° bag, it has kept me very comfortable into the mid 20s. Amazing that both of these bags are at least a pound lighter than the 15° bag and in significantly sharp contrast, are rated to give the user good notice as to what to expect out of it.

[Author]

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