I have a marmot sawtooth that I use for backcountry elk hunts and I like it a lot.  It's a 15 degree bag and combined with a pad, I have no problem staying warm (in fact I usually don't even zip it up all the way).
 
My .02 -  spend your money on good boots and a good sleeping bag, unless you find something on sale cheap 100 bucks doesn't buy much.  You have to remember on back country hunts weight is a issue but ALMOST equally important is volume.  Generally nicer -more expensive- bags are lighter and compress down significantly.  
 
Get EVERYTHING you THINK your bringing together and try and pack your bag- ha ha- you'll figure out that your gonna have to make some sacrifices and more and then some more!
My sleeping bag goes in a stuff sack that goes in a waterproof compression bag and rides outside my pack but I wouldn't want it any bigger than it is.

 Just my thoughts- pm me if you'd like more info- I would be happy to help as my yearly trip to the Rockies constantly runs thru my head

Sorry to disagree, but there are insulated air mattresses that provide 5 to 7+ R values that insulate quite well.

When down bags compress under your body they lose loft. Loss of loft is loss of insulation. Something like a BA Aircore or Exped Syn or Downmat has insulation inside of the mattress. No loss of loft, trapped air=insulation.

Will a $20 wallyWorld air mattress cut it, no. Proper tools proper job.

I use the Military Modular 4 part Sleep System with GORTEX Bivy Cover . That way depending on the weather you can sleep light +30 or down to -40 and waterproof if you use the outer shell. if in a tent dont use the bivey. They come with a compression sack. They are used on the big auction well under $100  for me the 7 lbs is worth sleeping dry and warm

Ajungilak Tyin Winter 180L Sleeping Bag, that's what I use since 1999. A Canadian Army sleeping bag worked wonders up in the mountains in 1998,too. Getting into the mountains ill eqipped will make for a very unenjoyable,potentially dangerous trip. Don't save on a sleeping bag and on a good shelter. A good self-inflating foam matress makes it much more pleasant to sleep on the ground.
My choice: Kifaru Tipi with Stove, Ajunkilak Sleeping bag,Kifaru Longhunter backpack, 1.5" self-inflating foam matress, Thin fleece blanket.
I mostly use the sleeping bag as a blanket only, the fleece blanket over the matress. If it gets colder, I zip the bag up. For base camp I use a go anywhere flat tent bed, matress in fleece blanket and a wool blanket over the sleeping bag as blanket to keep it from moving. I am a side/belly sleeper. Woll banket keeps the light sleeping bag in place.
The modular army sleeping bag doesn't sound bad either.

Best bag going for that money is the Kelty Cosmic 20 degree down bag.  North face cat's meow would be second...

I have done 6 backpacking elk trips in temps and conditions from one end of the spectrum to the other.  I have also done a good deal of backpacking in all the seasons.

I am not a gearhead.  I use what works for me.  A lot of it is attitude.

I have a Ridgerest sleeping pad that I bought for $.50 at a garage sale 15 years ago.  I have a Kelty 20 degree mummy bag that cost $59.00 in 1997.  Together they weigh just under 4 lbs.  

If it is cold, I sleep in my clothes.  

If it is really cold, I wrap a $2 mylar space blanket around my lower half on the outside of my bag.  Never put it around your face or condensation from your breath and the air leaking out of your bag will soak you.  I use a tarp as a shelter so condensation clears pretty well but it will still soak you.

X2 on North Face Cats Meow. Good bag under $200, weighs 2lbs 12 oz, and packs small. I've been using one for a couple of years now. It's a good bag for the money.

Keep your eye on Craigslist for inexpensive gear. Or good gear at a bargain.
From experience though. I wouldn't go cheap especially for carrying weight and warmth.  Also. A good pad is optimal. In my opinion. More important than the bag!
I have a big Agnes lost ranger. Light and warm. The plus side. The pad goes in a Sleeve in the bag and is always flat. Like WHIP I'm a side sleeper. But because of the design. The bag doesn't roll.
Weight warmth and design. Well worth the cost.
Good luck!!

I used a Wiggys bag while living in Southeast Alaska. I used it on goats & sheep hunts, etc.  Wiggys  

Looks like hey have 20% off and free shipping right now.

Second on Wiggy's. just picked up a 20 degree bag for 130.00.

i really like Marmot brand. they have a large range of prices. good gear.

I upgraded from  cabelas  xpg 20deg. Backpacker bag and Thermarest Zpad to  Big Agnes Lost Ranger and air core pad. Well worth the extra money you'll sleep better which means you'll hunt harder.

Steve

It might depend on what elevation you are going to be sleeping at.  I went to CO a few years ago in mid sept. and the temps were in the 70's in the day.  I had a name brand high quality 15 degree bag.  Camping at 10500' I froze!

mine is a Mountain Hardwear Lamina Ultra 0*....nylon shell, synthetic fill.  I like it because it is a full size for my 6'3" frame and allows movement in bag but not so big I waste energy warming the inside.  The fill is high loft and very insulating...you can get it with zipper on left or right per your preference....it has a draft tube and collar and enough room in footwell to allow you to keep some light clothing items down there to keep them warm or to throw a little pocket hand warmer thing you can buy at walmart to warm bag up.  I team it up with a insualated XLong Thermarest pad and is great for anything.
I got synthetic fill as where I live it is very humid so rain or high humidity is normal even in cold months.  I did not want anything that was going to lose loft in damp conditions or if it gets wet in my canoe (yes I use a dry bag)....  It is a mummy style but like mentioned with its size it is very comfortable and not restricting for me at all.  I would stay away from the waterproof shells....
If you are going to be out without a tent or tarp then I would just buy a bivy sac to go over it for that instant but otherwise get a regular constructed bag...you dont want it to hold any moisture in bag as that lowers your body temp in inclement weather just as wearing too many clothes in your bag will do.
I do recommend wool socks and a wool or poly/fleece head cover while in bag and then up to you whether you go commando or just very light synthetic underwear for sleeping.  Makes a huge difference in warmth and retention.

Good luck....I think my bag is like 3lbs...you can check it on MH website to be sure but very light and packs fairly small.  Wifes ia a Marmot...great bag too but for me the Mountain Hardware and Big Agnes were only two that gave me the warmth I required and the comfort I demanded being a larger framed guy.  A good solid sleep is important...

  Mountain Hardwear Syn Mens bags  


Can get through REI, CAMPNOR and Moosejaw for better pricing or buy last years colors...that is what I did about 4 years ago.

Try CampMor They have a good selection and I've used one of their lightweights for years. I would go with a synthetic. I would get a good ground pad. The self inflating mattresses are compact and light.
Also try Sierra Designs. They sell overstocks and have a good selection also.
Irv Eichorst
True South Adventures
South Florida outfitters for Hogs and Osceolas

I also recommend the Kifaru sleeping bags. They are definitely out of your price parameters, but I've not found a better more comfortable bag. In my opinion they give you the best combination of weight, warmth, and comfort. Obviously there are other good bags, but Kifaru is the best I have found.
Hope this helps.

I just took advantage of 20% off and free shipping at Wiggy,s. And they're making them custom so they can be zipped together for my wife and myself at no extra charge. Seem to be nice people to work with. And yes I know this thread was in 2013 but it's cold out. So I ordered 0° bag.

Carl

Since Carl is resurrecting this thread, I might as well spout off too.  I have backpacked a lot in the Wind Rivers of Wyoming and the Sierras in California, usually a month or two every summer.  For about the last 10 years, I have used a somewhat unorthodox system for sleeping.  The bottom half is an Elephant's Foot from Feathered Friends.  This is an ultra lightweight bag that only reaches about halfway up my chest, but has high quality down so my feet and legs stay warm. The top half is whatever the best down parka is that you can find or afford.  Mine is a Northface that reaches down below my butt, so there is quite a bit of overlap between the parka and the bag.

Usually I sleep on a Thermarest pad with my feet and legs in the bag and my parka spread over me like a blanket.  If it gets colder, I put the parka on and zip it up.  My arms are always free to stretch, never confined like in a sleeping bag.

At night if it gets cold before I go to bed, I put on the parka and am quite comfortable. Same thing in the morning when I get up; I just keep the parka on until it either warms up or I leave camp.

The combined weight of the parka and the bag is no more than many other bags alone, and I have found the combination to be much more versatile and comfortable than a full sized sleeping bag.  It also compresses and packs into the same stuff sack as a regular sleeping bag.

My parka is too much to wear around during the day unless I was on an Everest expedition, and too puffy to wear when shooting the bow.  But then, so is a sleeping bag.  If I were camping in extreme cold I would probably want something warmer at night, but this combo works fine for me down to about -5 or so if I'm in a tent and have a good insulating pad underneath.

McDave's idea sound interesting, but since I have a 0* Wiggy's I'll have to go with that.

McDave's idea was pioneered by climbers back in the 60s and 70s, who used it to conquer a lot of mountain summits. Here is a link to images of some  half bags with parkas .