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Along with that I use a Big Agnes Insulated Core air pad. specs @ 21oz

For cold weather conditions I also use a cut to fit blue foam pad that I slip in the sleeve along with the air pad.

I do not, or will not get cold

5 yards of insulation, 5 yards of fabric. You'll only use about 4.2 of each. Materials weigh in at roughly 30 ounces for a full size bag. That's less than 2 pounds. That's less than commercial offerings due to the nylon. Commercial bags use heavier shells to cover the wide base use that comes from different users. However, the 1.1 nylon works just fine. No more narrow foot beds of the mummy bags if you don't want it.

This insulation doesn't have to be baffled either. Pin it to the shell and sew the edges. Done. Compresses almost as small as down. It doesn't get damaged by compression. Heats when wet too. Dries fast also. This Synthetic is top notch and AFFORDABLE when you do it yourself. God Bless

Sure WM bags are awesome, (I too have a Sequoia) but they aren't nearly as packable, heavier and cost three times as much. I use WM late season, but would never get rid of my BA bags for early season. I like their down-tek bags. Own three of them along with the WM Sequoia and a Kifaru Slick Bag.

ED

Another consideration is down vs synthetic. Most down doesn't dry when wet but if you hunt relatively dry areas and keep your bag in a dry bag you it may work fine. Down is super nice because it is super light and compact. Some down bags have water resistant outers.

You usually pay for what you get with sleeping bags. It's pretty tough to beat WM. I've used a Marmot down bag with a water resistant outer for years and had great results. I've brought it on several trips to Alaska and use it in Colo, Wyo, and other Western states every year.

I, too, use a 0 bag in September. That means a real "15-20" bag for most people, and at elevation in CO it isn't unusual to have sub-20 mornings.

I also have a Marmot 15 and it's fine for summer backpacking and scouting at 10K+, but I've been cold in it in September, which is why I invested in a 0.

My philosophy is that a well-rested hunter is a better hunter. I endure a few pounds for a good tent, pad, and bag and cut back elsewhere.

Plus, the OP wanted lightweight, not ultra light

Keep in mind too,that temperature ratings are subjective.Western Mountaineering's ratings are conservative compared to many.I don't sleep that warm but I wouldn't be afraid to stay stay out in this bag at 0.It's really too warm for September hunts in the mountains.

Western has both roomy mummies as well as semi-rectangular bags.If I get another one for Fall bowhunts,it will be either a semi-rectangular Sycamore or an Alpinlite which is a fairly roomy mummy.Both are 2 lb bags.Good luck with your choices.

I've used the Mountain Hardware phantom 32 (just under a pound) for the last 10 years. On warm nights, it was perfect, on cold nights I slept in my puffy.

But on wet nights...or when I hadn't managed the dew point...I was totally miserable.

The down compressed immediately and by morning, I was shaking, or just tired.

I bought a water treated down jacket to determine if it would be worth while buying a treated down sleeping bag. And, to be honest, the treated down just does not hold up for the length of time that you'd be spending in a wet bag (i.e. a full night...more than an hour or two).

So, I've committed to buying an ultralight synthetic bag. Previously, this was somewhat of a misnomer as ultralight synthetics were hard pressed to fall below two pounds.

I just bought a 23 degree Mammut for less than $200 that weighs 1 pound 15 oz. In my opinion, synthetic provides the best balance between confidence, warmth, and weight.

With most backpacking gear... all else being equal in performance, money buys you less weight/bulk. Jims nailed a bunch of it.... some depends on are you a hot of cold sleeper. My thermostat is set higher than most, I'm always traveling from 80's tropics to fall mountains, usually in a matter of hours. Body is still set on dealing with heat, not staying warm.

Temp ratings are normally set by salesmen, not the designers. Like with many things, people spec hunt. Sales fudge the specs to compete better. WM is one of the few that IMO use a true "comfort" rating and not "survivable" ratings. I've been toasty warm at 17 in my 15 bag. If looking at other bags a person should consider that.

If I were in constantly wet conditions such as much of AK then I'd consider a synthetic bag. They have come a long way the last few years. But then so has bag cover material. Been in a few spots were it rained for several days.... left the down bag in a drip zone once during the day, but the bag came out of it just fine.

Also don't forget... it's called a sleep system. A good quality pad makes a huge difference. One of the neat things about big aggie is how their pad integrates with their bags in a sleeve.

Link

http://www.bigskyfishing.com/camping-gear/sleeping-bag-temperature-ratings.php

Ed

http://www.backcountry.com/explore/warmth-to-the-wise-temperature-ratings-for-sleeping-bags-decoded

I tend to sleep about 10 to 15 degrees colder than a decent quality bag's temp rating. But carrying too much weight with too much bag is not a pleasure either.

I've learned that on the colder nights to drink a cup of hot water before turning in. No tea, hot chocolate, etc, just water. Being cold is enough to have me constantly peeing through the night and caffine/sugar exacerbates that. Just a cup of hot water is all it takes without waking constantly.

I believe this helps because I don't start out in my bag at a temp deficit that rarely catches up through the night. By starting out warmer on my inside I don't chase warmth as my body slows down sleeping.

Give it a try sometime, you might just find your nice light bag is nicer than you thought.

Andy

As for the Western Mountaineer stuff -- its great gear no doubt. But $500-800 is not something I'm ready to spend on a peace of gear that will fail if wet when I can spend a fraction of that and get a peace of gear that won't (or will to a lesser extent).

I would also emphasize getting a good pad. You loose 30% of your body heat through the ground and a good pad has really helped (saved?) me in the past. I've used exped for a while now and their customer service is right up there with vortex.

A nice pad gives you the option of getting a lighter bag.

The temp on Friday night dipped to about MAYBE 35-40 degrees. I slept with socks and briefs on and I froze my ass off until I said screw it and put my pants and a shirt on.

I was not impressed. I was hoping I found the perfect lightweight synthetic option, but now I'm back looking for something similar since the Mammut I was looking for is not available.

Anyway, just an update.