Mountain Hardwear Big Bang SL

2 reviews
5-star:   1
4-star:   1
3-star:   0
2-star:   0
1-star:   0



Tested in 3 different scenarios. 1 - initial test.

Rating: rated 4 of 5 stars
Design: mummy
Fill: down
Temperature Rating: -15 f
Price Paid: $450

Tested in 3 different scenarios.

1 - initial test. I waited until a storm hit. Temperatures ranged from 35 to 20 F, wind gusts at about 30 mph, dense rain. Outdoor Research Advanced Bivy made from GoreTex.

I camped in my backyard for the initial test. I used the bivy and no tent.

I got in the bag at about midnight. The storm was in full effect. I was soooooo warm I had to unzip most of the bag and vent the bivy.

I could see my cat watching me intensely for hours from the glass door facing the yard.

At about 3am, I heard meowing from the head end of my bivy. My cat was wet, covered with snow and it seems like he was out there waiting for at least 30 minutes in the storm. So I let the poor thing in, soaked fur and all. He crawled inside the bivy then inside the BigBang. We both slept very well the rest of the night.

2 - ADKS winter storm -6 F 50 mph gusts. About 2000 feet base camp. Inside a expedition tent. Tooooooooo hot! had to leave the zippers open. during the night condensation built up a LOT because I didn't vent the tent enough. Lots of condensation near the head of the bag, but the conduit kept the moisture from getting in. I was dry and warm.

3 - ADKS. Due to bad planning I got stranded on the peak on Marcy. Temperatures 25 to 35 F. Rain and snow. 50 MPH gusts. I set up a emergency shelter with my tarp and bivy. During the night condensation created small pools of water on the floor of the bivy. I was dry, and warm. I slept better stranded on the mountain in my bigbang then I did at home in my bed.

This is a well made bag!!!!!!
I never used it in -15F, -6F is the coldest, and it was very warm. At -6 F the bag needs to be vented to stay cool.

This bag is tough and water resistant. The extra room created by the bigbang feature allows a pet to crawl in when the inner zipper is expanded.

A tarp or a bivy and this bag is all one needs.


I have slept in over a hundred sleeping bag types,…

Rating: rated 5 of 5 stars
Design: mummy
Fill: 600 fill down
Temperature Rating: -15
Weight: 3lbs, 2 ozs.
Price Paid: $350

I have slept in over a hundred sleeping bag types, and prior to this one my favorite was the military extreme cold bag. But it weighs 11 lbs and is big, heavy and awkward to backpack with. But, warm and comfortable.
However, because I could not see what could be done to a sleeping bag to make it worth that much, I was not willing to pay $300 + for ANY sleeping bag; this was given to me as a gift. Today, if anything happens to that bag, I won't even flinch at paying $350 for a replacement.

Though I have not slept in it to -15 deg. yet, I have tested it 'outside'. to 0 deg. It is the most comfortable bag I have ever slept in. Unlike the military bag, that bunches to your clothing, this bag seems to just slide up and enfold you. Most bags have a few minutes waiting period, that your body must shiver in to warm it up, but not this one. As soon as you're in, you're warm!

There was an outing in which I took my two Boxer dogs with me. I woke up in the middle of the night, and despite them having a thick blanket and each other to snuggle to, they were both shivering. I unzipped the 'draft tube' to make more room then unzipped the bag and invited them in enough to just lay a part of the bag over them, with me in it. Their bodies blocked the cold from me and we ALL slept toasty that night.

The weight and size of this bag when compressed is quite adequate for backpacking, though as any backpacker will attest, the smaller, the better. I carry a hammock and ponchos for shelter (as I'm 56 yrs old and can no longer sleep on the ground due to my back) and sleeping in a hammock is true testimonial for a quality sleeping bag, since you have the wind blowing above AND below you. Of course there are ways around that for a seasoned camper, but I have never had to implement them yet.

I have nothing but praise for this bag!

Retailers' Descriptions

Here's what other sites are saying:

The Big Bang? is an ideal winter bag for snow camping and back-country skiing. Constructed with Mountain Hardwear?s exclusive moisture shedding Condui...

- Ramsey Outdoor

Rated to -15F, this high-grade down bag offers up an expandable girth, allowing you to sleep through a much wider temperature range than previously possible. Expandable draft tube offers up to 8 inches of girth, meaning that the bag can still be comfortable when the temperature rises up to the teens. 600-fill goose down is compressible, long lasting, and has a terrific warmth-to-weight ratio. Conduit SL shell is windproof, water resistant, and highly breathable. Down-filled draft collar seals in heat below shoulders. 4-panel contoured hood seals in heat, exhausts moisture. Full-length insulated zipper gusset prevents heat loss. Multipaneled footbox for enhanced thermal performance. Snag guards prevent zipper snags.


FeaturesTuck-stitched baffles prevent threads from snagging and breakingFace gasket seals in heat around faceAlpine mummy cut is more efficient and saves Weight:, reducing girth at shoulder, hip & legsEight-baffle, tailored hood is warm and comfortableConduit SL - waterproof and breathableInsulated draft tube extends to bottom of bag and is not sewn throughTie-in loops stabilize upgrade linerInsulated, ergonomic draft collar seals in heat below the shouldersExpandable draft tube provides additional room for warm temps and layering space for colder tempsSnag guards prevent fabric from catching in the zipperSingle-handed differentiated drawcords (round black elastic and flat silver tape) simplify adjustment of hood and collarNylon mesh storage sack and stuff sack includedOverfilled, ergonomic draft collar seals in heat below the shouldersBox baffle construction ensures maximum Loft: with minimum Weight:Two-way locking zipper sliders stay in place when ventingMulti-baffled Comfort Footbox follows natural foot position for improved fit and warmthDifferential cut maintains maximum Loft:Tight 5in. baffle spacing keeps down from shifting and prevents cold spotsVelcro tab at zipper sliders stay in place when venting SpecsWeight: 3 lb 14 oz / 1.8 kgTemp Rating: -15 F / -26 CFill Type: DownSizes: REG,LONGFill Weight: 2 lb 1 oz / 936 gLoft: 8 in / 20.3 cmInside Length: 6 ft 6 in / 2 mShoulder Girth: 5 ft 1 in / 1.5 mFoot Girth: 3 ft 3 in / 1 mStuff Diameter: 10 in / 25.4 cmStuffed Length: 1 ft 6 in / 45.7 cm

- Moosejaw

Big Bang lets you buy just one sleeping bag to use for cold, demanding trips, as well as milder-weather backpacking outings. Quantum Expander allows unparalleled versatility; zip it up for a snug, more technical fit or unzip it for 8" added girth, yielding a roomier bag. Bag has been reshaped to bring the down insulation closer to the body, without being uncomfortably restrictive. Specifically, room has been added at the elbows and hips, while reducing volume around the head and from hips to knees. Conduit™ SL shell is water-resistant, windproof and extremely breathable; warm 600 fill-power goose down is lightweight and compressible. You can enjoy all the comforts and benefits of goose down, plus feel free to use this bag in wet conditions. Box baffle construction creates maximum loft with minimum weight; 5-inch baffle width keeps down from shifting and prevents cold spots. Warmth is optimized by differential cut of shell and lining, allowing the goose down adequate room to expand to its full loft. Ergonomic overfilled draft collar drapes comfortably over neck and shoulders, sealing out drafts. Multi-baffle, tailored hood has a down-filled face gasket which makes hood closure more comfortable and effective. Multi-baffle Comfort Foot Box is shaped to allow feet to rest naturally; shape preserves loft and allows down to drape closer to feet for more warmth. Two-way, locking, snag-resistant zipper sliders stay in place when venting. Comes with mesh storage sack and waterproof stuff sack.


Mountain Hardwear Big Bang SL


The Big Bang SL has been discontinued.

previously retailed for:
$279.95 - $365.00

The Mountain Hardwear Big Bang SL is not available from the stores we monitor. It was last seen August 12, 2008 at Ramsey Outdoor.

If you're looking for a new cold weather down sleeping bag, check out the best reviewed current models.