400 Legend, By the Numbers
Winchester introduced 400 Legend in 2023 and SAAMI accepted it that February at 45,000 psi with a reference load of a 215 gr bullet at 2,230 fps. Like 350 Legend it exists for the straight-wall deer states, and Winchester positioned it deliberately between its own 350 Legend and the .450 Bushmaster: about 25% more energy than the 350, about 20% less recoil than the .450, and a bullet diameter (.40 caliber) that meets the straight-wall rules everywhere the others do.
The case is a straight-walled .40-caliber case with a .422″ rim, the 6.8 SPC rim, so it runs in an AR-15 with a 6.8 SPC or .224 Valkyrie bolt and its own magazines. Winchester’s loads are a 215 gr Power-Point at 2,250 fps (2,416 ft-lb), a 190 gr Deer Season XP at 2,400 fps, and a 300 gr Super Suppressed subsonic at 1,060 fps for suppressed use. That is a 300-yard deer cartridge in the field and a quiet one with a can on.
Faxon builds it on the Gunner Big Bore contour: a straight .875″ body for the wide case, an .875″ × 1.9″ gas journal, carbine-length gas, and 11/16x24 threads that pass the .40-caliber bullet. Twist is 1:16, 6-groove, which stabilizes the 190 and 215 gr hunting loads and the 300 gr subsonic. Read 350 Legend vs. .450 Bushmaster for the cartridges it sits between.
Winchester factory data — test barrel length not stated
| Load | Bullet | Muzzle velocity | Muzzle energy |
| Winchester Power-Point | 215 gr Power-Point | 2,250 fps | 2,416 ft-lb |
| Winchester Deer Season XP | 190 gr Extreme Point | 2,400 fps | 2,430 ft-lb |
| Winchester Super Suppressed | 300 gr Open Tip, subsonic | 1,060 fps | 748 ft-lb |
Source: Winchester’s 400 Legend launch data as reported in the trade press; Winchester’s product pages did not show ballistics tables when checked, and the Deer Season XP and Super Suppressed figures are Winchester specifications as listed by retailers. Test barrel length is not stated; expect a 16″ to run at or slightly below these figures.
The Duty Series 400 Legend Barrel
All 1:16 twist, 4150 CMV, QPQ nitride inside and out, 11/16x24 muzzle. Weights are nominal; prices are MSRP.
What You Need to Build It
A 6.8 SPC / .224 Valkyrie bolt carrier group (the .422″ rim), 400 Legend magazines, a mil-spec AR-15 upper, and a standard barrel nut; Faxon’s Big Bore upper, with opened feed ramps and ejection port, is recommended for the straight case. The barrel takes an .875″ gas block on a 1.9″ journal and a carbine-length gas tube. Muzzle is 11/16x24 with a .40-caliber bore, so it takes 11/16x24 devices with a .40 or larger bore, or a .45-rated suppressor on an 11/16x24 mount.
What Every Duty Series Barrel Shares
Duty Series is Faxon’s 4150 CMV line: the M4/M16 barrel alloy, button rifled, stress relieved, and salt-bath QPQ nitrided inside the bore and out, which hardens the surface while adding virtually nothing to it, roughly a tenth the width of a human hair, and leaves no plated layer to wear through. Every barrel is turned, crowned at 11°, chambered, 100% wet magnetic-particle inspected, and nitrided, then has its gas port drilled and reamed and its extension torqued to 150 ft-lb, pinned, and headspaced with a go/no-go gauge, and is laser-engraved with the Faxon shield, order number, and cartridge and twist, in Faxon’s Greater Cincinnati, Ohio plant. Faxon’s AR-15 and AR-10 barrels have been voted Favorite Aftermarket Barrel by Shooting Sports Retailer every year since 2022. All Duty Series barrels › All rifle barrels ›
Duty Series 400 Legend FAQs
What bolt does 400 Legend use?
A 6.8 SPC / .224 Valkyrie bolt, because the 400 Legend case has a .422″ rim. A 5.56 bolt will not grip it and a .458 SOCOM bolt is too large. Faxon’s 6.8 SPC / .224 Valkyrie bolt carrier group is the pairing.
How does 400 Legend compare to 350 Legend and .450 Bushmaster?
Winchester built it to sit between them: about 25% more energy than 350 Legend with a heavier .40-caliber bullet, and about 20% less recoil than .450 Bushmaster with nearly its energy. If the 350 feels light for big-bodied deer and the .450 kicks more than you want, this is the cartridge.
Is it a 6-groove barrel?
Yes. The Faxon 400 Legend barrel is 6-groove, 1:16 twist, which stabilizes the 190 and 215 gr hunting loads and the 300 gr subsonic.
What muzzle devices fit?
11/16x24 devices with a .40-caliber or larger bore, which in practice means devices made for 400 Legend, .450 Bushmaster, and .458 SOCOM, or a .45-rated suppressor on an 11/16x24 mount. A 5.56 or .30-cal device will not pass the bullet.
Ballistics are manufacturer-published figures from the test barrels stated; velocity estimates for other lengths are approximations, not Faxon chronograph data. Dimensions are from Faxon engineering prints; weights are nominal. Prices are MSRP. Check your state’s hunting regulations before choosing a cartridge.
