Item: MSR AC Bivy
Rating: 3.5
Author: Paul Turner

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If you have been deciding which bivy to buy, this MSR AC Bivy Review can help you to better narrow down your choices for the bivies out there.

While tents protect campers from natural elements such as the sun, rain, the wind and also bugs, it also takes up the campers time to set everything up. A bivy is great for someone who is looking for a quick overnighter. While it takes little to no setup time, it can also offer protection like the tents.

As a product that comes from MSR, the AC Bivy is quite the popular bivy that people look at. However, there are not a lot of websites talking about this product.

Our Rating:

Pros

Ultralight for minimalists
Durable floor so you can feel safe with it on rough floor
Compact size
Easy entry and exit

Cons

Expect condensation
Mesh rests on your face, bugs will be able to eat your face
Not made for cold weather

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Key Features

Ultralight Weight
Nylon Fabric with DuraShield coated floor
Envelope style hood allowing easy entry

Weighing only 1lbs, this bivy ensures it will be the last thing you complain after a long hike. However, to skim on the weight, a couple of things were traded off.

The body is made of ripstop nylon fabric. This material is waterproof, strong and breathable.

The space is relatively smaller as compared to other bivys. The envelope style hood does not have any zipper. This saves some weight, you can quickly slip into the bivy and close it up. However, this also allows strong wind to blow it open, letting some rain to leak inside.

Let’s look at individual components of the Bivy.

Detailed Review

Ease of Use - 4/5

There is no setup needed to use this bivy. There are no poles to insert into the hoop. It is also very simple to use. All you need to do is just to lay the bivy on the floor and slip your body inside.

There’s a zippered mesh at the top if you want ventilation and protection from bugs. The envelope style hood does not have any zipper. If you want to close the bivy, you can pull down the hood to close it. However, it’s not a complete closure as the wind can still blow open the hood.

Getting in and out of the bivy is fast as you there is only one zipper to open or close. This bivy can be especially useful when the weather is unpredictable. You can get almost instant protection because you don’t have to set it up and it is easy to get inside.

Weight - 5/5

This bivy definitely gets the full marks for weight. For minimalists that want to save on every ounce in their backpack, this bivy sack can be considered. Your sleeping bag or pad might be even heavier than this sack.

However, to achieve such weight, the bivy has sacrificed space and zippers. This still does not matter much as the length of the sack is long enough to sleep one person and store a backpack. It will get pretty squeezy if you have more items to put inside the sack.

Although the AC Bivy is ultralight, it is still not the lightest in the market. There is an even lighter bivy sack out there like the Black Diamond Twilight Bivy.

Packed Size - 4/5

The purpose of a bivy sack is defeated if that sack is going take up a huge portion of space in your backpack. Luckily for this sack, it packs up to a size slightly larger than a 1-litre water bottle.

The stuff sack to store the bivy is very small. You have to heavily compress the bivy to fit inside the stuff sack. This may not be a big issue since most of the times you will be packing the sack are when having slept enough and continuing the hikes. By then, you will have enough energy to shrink the bivy. However, it might get frustrating if you keep trying to squeeze it into the stuff sack.

Wet Weather Usage - 3/5

The fabric is rated to withstand 10,000mm of water pressure. This rating shows that the bivy sack is generally waterproof. By closing up everything in the bivy, you should be safe from the storm.

However, as it does not have a zipper to close up the hood, it does not offer complete protection from the rain. If there is wind accompanying the rain, it can blow open the hood and let the rain leak into the bivy sack.

Hot Weather Usage - 4/5

This bivy will do well in fair weather seasons. There is ample mesh to allow the air to flow freely in and out of the bivy sack. The fabric is made of nylon which is also a breathable material.

With ample mesh and breathable material, the bivy sack becomes well ventilated and heat won’t be trapped inside.

Cold Weather Usage - 1/5

Unfortunately, this bivy will not do well in cold weather seasons. The envelope style hoop still allows some cold air to enter the bivy even its closed. This cold air enters the bivy and through the mesh.

Not only it will get colder inside the bivy, your face will be the first to be affected by the cold air.

Comfort - 3/5

There is a generous amount of width to move your shoulders inside the bivy sack. The length is also good enough to sleep a tall person and leave some space for other items. If you don’t have a lot of items to store inside it, it will be quite comfortable to sleep in it.

The mesh is also designed to keep bugs out. You won’t be accompanied by those pesky insects unless you didn’t zip the mesh properly.

There are no poles to bring the hoop or the mesh up. This is rather unfortunate as there might not be any gap between the mesh and your face. You might end up having bugs sitting on your face at night. Furthermore, the feeling of fabric rubbing against the face can be quite irritating.

Durability - 3/5

Feel free to toss the bivy sack onto a rough terrain. The floor is made from a tough material. it is also treated with Durashield PE coating, giving it even more strength to hold against rough surfaces.

However, the top is thinner as it does not have any coating so you have to be careful handling the top.

Overall Score:

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How Does It Compare To Others?

Outdoor Research Alpine Bivy

The Outdoor Research Alpine Bivy offers protection for almost everything. It uses GORE-TEX fabric which is very breathable. There is also a vent at the bottom to provide even better ventilation.

When setting up, the poles brings up the hoop, creating space between the head and the hoop. You won’t be having fabric rubbing against your face. This makes it more comfortable compared to the AC Bivy.

The hoop also has a zipper. This allows it to be completely closed when there is a need to. No cold air will be able to enter the bivy if it is completely closed. If you need to go to colder places, you should get this bivy instead.

Although it offers so much protection, it is quite bulky and heavier. The size is also smaller as compared to the AC Bivy. If you are not going for a long hiking expedition where weight is going to be an important factor, you can consider this bivy.

Black Diamond Twilight Bivy

There are not many feedbacks on this product but I would say it is similar to the AC Bivy. It is a frameless system so there are no poles to set up. Because there are no poles to put the hoop up, you will still face the same problem of having the fabric touching your face.

A user mentioned that it is not waterproof so you might want to consider other choices if you heading to wet weather places.

This is an even lighter bivy sack. If you are looking to shed even more weight in your backpack. This can probably be one bivy to consider.

Slumberjack Contour Bivy

The weight is in between the AC Bivy and the Outdoor Research Alpine Bivy. It offers better comfort than the AC Bivy as the hooped hood gives enough space between the head and the mesh window.

The Slumberjack Contour Bivy also comes with additional features like multiple zippers and arm openings. This bivy provides even easier access than the AC Bivy as you can zip from the top or from the bottom. If you want to cook your meal or just move your hands around, you use the arm openings while still being protected from the rain or bugs.

If you are okay with a little more weight in your backpack, you can consider this bivy as it offers more useful functionalities and comfort.

Should you buy?

In my opinion, I will rather go for the Slumberjack Contour Bivy because I think that the extra functionalities and comfort is worth the extra weight.

If you are someone who is going to save as much ounce as possible, you can consider this or the Black Diamond Twilight Bivy. But, do expect there will be some rain entering the bivy or the discomfort of fabric on the face.