Osprey Mutant 52L Review

The Osprey Mutant 52 is an excellent all-around mountaineering pack for longer trips, more complex objectives, and multi-day adventures in winter conditions.

Performance Comparison

Versatility

The Mutant 52 is not quite as versatile as its smaller cousin, the 38-liter, but is still highly versatile. Due to the larger size, this pack will cover a broader range of activities that require more gear or more days than the 38 could manage.

The 38 and 52-liter versions overlap in the 3-5 day summer mountaineering objectives. The 52-liter backpack will certainly work for fast-and-light summer climbs, but it will feel a bit bulky and cumbersome. That said, if you're looking for a true quiver-of-one mountaineering backpack, this is a solid candidate.

Weight to Volume Ratio

The Mutant 52 does not hold quite the same standard in this metric as its smaller cousin, the 38-liter version. We think the main reason it falls behind in this category is due to the collar design of the main compartment. This pack has an asymmetrical collar that does not extend upward in a cylindrical fashion like most similar mountaineering packs. This makes the opening very wide and makes packing easier, but it reduces the amount you can cram into the top of the backpack. With a more cylindrical collar, you can stuff a lot of compressible items into every inch of the expandable space, then compress it all down with the rope keeper strap or the lid of the pack.

Otherwise, the material and ease of packing remain similar to the Mutant 38, with slightly stretchy fabrics that allow you to squeeze something into every last inch — up until you run out of room at the collar. To keep this pack reasonably comfortable, we think it was a wise choice to limit the size of this pack and make it difficult to truly overstuff.

Osprey advertises this pack at 52 liters, but in our ping-pong ball volume test, we measured 47 liters. The 38-liter Mutant measured 37 liters in our test. Subjectively, we also felt that the 52-liter Mutant did not carry quite as much stuff as other 50 liter packs. But remember that there does not seem to be any industry standard on reporting pack volume, which is why we measure ourselves. Some manufacturers seem to include pocket volumes. For consistency and comparison, we only measure and report the main compartment's volume.

As climbers, we are always trying to carry the smallest pack possible to improve comfort on the technical part of our climb — at a slight cost to comfort on the approach. Osprey keeps us honest with the Mutant 52 by truly limiting how much we can overstuff this pack, forcing us to be thoughtful about what we bring. And realistically, with good strategy and a little thought, this pack works out very well for multi-day mountaineering objectives.

Comfort

Since we tested the Mutant 38, we have been dreaming about a pack of every size made in its shadow. Osprey answered our dreams with the 52, one of the most useful and versatile pack sizes for mountaineering.

We had already been pushing the limits of our 38, loading it with up to 5 days worth of food and gear for summer mountaineering trips. With the 52, this was a much more reasonable endeavor, and we could fit more items inside the pack instead of looking like a walking yard sale.

The back panel of the Mutant 52 has a removable plastic sheet with two metal stays. This sheet provides excellent support for heavier loads and is very easy to remove when you get to basecamp and gear up for a technical climb or ski descent. There is also a removable foam sheet in the back panel. If you leave this in place, it makes for an excellent, comfortable summit pack. It is just thick enough to provide a smooth yet supple surface that contours to your back, making it feel secure, ensuring the pack moves well with you on the technical portion of your climb or descent. When the pack is full with your equipment for basecamp, we recommend keeping that plastic sheet in place so you don't end up with a fuel canister pushing awkwardly on your back.

Admittedly, for many objectives, we still choose to cram our 38 to the max to have the climbing comfort of the smaller bag on the technical portion of a multi-day climbing trip. The comfort and more compact size are outstanding. However, the 52 fills a very important niche. For winter mountaineering or multi-day ski touring (trips where you need a bigger sleeping bag and more puffy layers), this larger version provides very impressive comfort on the approach, a secure fit for skiing, and excellent ease of movement on climbs. This is an impressively comfortable backpack for the 50-liter size range, only moderately less comfortable than its smaller counterpart.

Durability

The 52-liter Mutant is nearly identical to the 38-liter version: same colors, similar features, and roughly the same materials (which is sometimes confusing when we go to grab the pack from our gear closet). This pack also features mostly 210 denier high tenacity nylon. This fabric is a good compromise between lightweight and durability.

In our extensive field testing, we had no durability issues whatsoever with this pack — no holes or signs of abrasion on the fabric, and no bursting seams or manufacturing failures. We loaded this pack down and stuffed it to the brim, and this Mutant adapted to it all.

Features

The Mutant series is aptly named — it can change and adapt to a variety of conditions and applications. The 52-liter size is a fully-featured mountaineering backpack suitable for ski mountaineering, summer and winter mountaineering, ice and alpine climbing — just about anything the mountains might require.

From top to bottom: we love the helmet carry on top of the lid — this reduces the risk of dropping your heavy pack on your helmet (many helmet carries put the helmet on the front of the pack). We love the removable lid and the flap underneath that covers the pack's opening when you remove the lid. Sometimes we would mix up the buckles for the flap with the buckles for the lid, so some color coding would be nice there.

Many lightweight packs eliminate features to keep them light — the Mutant series remains impressively lightweight without eliminating any features. This is most notable with the side straps — this is a great pack for ski mountaineering, as you can easily slide your skis through the burly side straps and carry them in an A-frame.

The pack also has one of our favorite ice axe/ice tool attachment systems. It has T bars with elastic that thread through the head of your axe or tool and a simple sleeve to tuck the pick into and secure it in place. Some packs use a buckle around the head of the axe, but this sometimes doesn't work for technical tools — the head can be too small and slide out of the strap.

There is a daisy chain of thin webbing sewn to the front of the backpack which perfectly fits a standard ski strap (which you must purchase separately, and which we highly recommend carrying as an addition to your repair kit anyway), and allows you to strap crampons to the front.

The hip belt has gear loops on each side, making it easier to access your cams and carabiners on technical climbs. The hip belt can make it harder to access gear on your harness, so this is a nice feature to keep things close at hand.

Value

The Osprey Mutant 52 is well-priced for its size and a great value all around. It is the biggest in the Mutant series, and it is less versatile than the 38-liter version for all-around alpinism. But for slightly longer trips, up to a week for summer trips with an ultralight kit, more gear-intensive trips in the winter, or for more complicated routes involving glacier travel, snow, ice, and rock, this pack will be an ideal companion.

Conclusion

The Mutant Series is our favorite fleet of fully-featured mountaineering backpacks. There are certainly other packs that we prefer for certain types of climbs, but for all-around mountaineering purposes, the Mutants are hard to beat. The 52 is our dream come true for a pack in the 50-liter range, offering more volume without much cost to carrying comfort. It is not quite as comfortable as its smaller cousin, the 38-liter version, but it is far more comfortable than other 50 liter packs we have tested. Now we are dreaming of a Mutant in the 70 and 100 liter ranges for expedition use!