18″ 400 Legend Medium Carbine M-LOK Upper Assembly

A premium upper assembly engineered for straight-wall performance without compromise. This means starting with a top tier mil-spec forged upper receiver, using a nitrided steel gas block as opposed to phosphate or aluminum, quality American Made M-LOK handguards and one of the finest nitrided barrels you’ll find anywhere. This also means taking the time to ensure that the upper will function flawlessly with Winchester’s innovative 400 Legend cartridge. We use Permatex 242 on key components while using mil-spec AEROSHELL 33MS Anti-Seize grease on the properly torqued barrel nut and muzzle device.

Bottom line is this: you hear all the time about guys buying a budget upper and it not delivering the knockdown power that the 400 Legend was designed for, or having to send it back because of some hardware defect or other issue caused by a careless assembly process. That is why we use top tier components and assemble each unit to the highest standard of quality. We want your upper to deliver the exceptional hunting performance that makes 400 Legend the perfect middle ground between power and shootability. In fact, we guarantee it will.

Buy with confidence, this upper is backed by our 30 day satisfaction guarantee. Buy it, run it, take it hunting, and if you aren’t satisfied you can send it back for a full refund.

Handguard style may vary from batch to batch

Lifetime Warranty

Guaranteed Sub-MOA performance with quality hunting ammo and proper shooting technique

Made in the USA

The 400 Legend Advantage – Winchester’s Perfect Balance

The 400 Legend represents Winchester’s masterful solution to the straight-wall cartridge dilemma. Introduced in 2023 and SAAMI-standardized, this cartridge was specifically engineered to bridge the gap between the lighter 350 Legend and the hard-hitting 450 Bushmaster, delivering what hunters in restricted states have been waiting for.

The Goldilocks Cartridge: The 400 Legend hits the sweet spot that hunters have been seeking. It delivers 25% more energy and greater penetration than the 350 Legend, while matching the energy of a 450 Bushmaster but with 20% less recoil. This makes it the ideal choice for hunters who want more authority than the 350 offers without the punishing recoil of larger straight-wall cartridges.