Mountain Raid 303 Synthetic Sleeping Bag

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Ultralight, race-ready, and tailored for fast-moving mountain nights in mild weather.

OMM says

We said we’d already made our warmest sleeping bag a year or two ago with the 233 but this time we really mean it! With 3 times the fill of our lightest weight options, this is the bag for those that sleep cold or are looking to extend their camping season into the colder months.

Like all our sleeping bags, the 303 uses PrimaLoft® Cross-Core Gold Eco insulation, which performs even when wet, if you are inundated. A half-length zip reduces cold spots and overall weight whilst a close-fitting, adjustable mummy-style hood helps trap the maximum of heat. A tapered fit reduces dead air and the shaped footbox makes for a more comfortable sleep position.

Like all our sleeping bags, we take this high-quality insulation and map different weights per panel to ensure the best usage of the fill. The base sheet is filled with PrimaLoft® Cross-Core Gold Eco 133g/m2, whilst the top layer, above the sleeper, is 170g/2 (giving us the 303g/m2 total in the name). Mapping the insulation in this way allows us to achieve such a low pack weight, there is no point placing excess wadding (and therefore weight) beneath the sleeper, as the weight of their body will compress it and reduce its ability to trap air and insulate. Instead, we focus the warmth on the top sheet and leave it up to you to decide what mat to use to insulate you from the ground.

Our Verdict

The OMM Mountain Raid 303 is purpose-built for those who prioritise minimal weight and resilience in damp conditions. At 624g, it offers a streamlined sleep solution for fast packers, mountain marathoners, and adventure racers seeking a compact synthetic bag that handles milder conditions.

Insulation is carefully mapped, with 170g/m² across the top and 133g/m² underneath, utilising PrimaLoft Cross-Core Gold to balance loft, compression resistance, and drying time. The warmth feels appropriate for temperatures around 10°C. The PointZero shell and water-repellent treatment keep light moisture at bay, while the half-length zip reduces weight and heat loss, though it does limit ventilation options, and it’s a bit of a chore to get in and out of. 

Fit is slim and athletic. The close mummy shape and narrow footbox increase thermal efficiency, but movement is restricted, especially for taller users. Comfort is best suited for those who sleep straight and don’t mind a snug fit.

– Reviewed by Ultralight Outdoor Gear

Features

• Thicker insulation top than base
• Half YKK® zip
• Stitched through inner with loose laid outer
• Fast drying easy care
• 195cm long mummy shape
• Shoulder Width 65cm
• Pack Size 30 x15 cm
• Hood drawcord
• Hang loops at base

Specifications

• Weight: 624g (ex bag)
• Tog: 7.9 / 8.0
• Pack Size: 30 x 15cm

Material & Construction

• PointZero – 100% 22gsm nylon ripstop fabric, downproof, highly wind resistant with DWR
• Primaloft ® Cross-Core ECO GOLD – 133/170g
• 90% Recycled Insulation
• Insulation rating DRY – 7.9 TOG
• Insulation rating WET – 6.0 TOG

Help and advice:

• The Ultimate Guide to Lightweight Sleeping Bags
• Sleeping Bag Shapes & Sizes
• Down Quality