350 Legend, By the Numbers
Winchester introduced 350 Legend in 2019 and SAAMI accepted it the same year at 55,000 psi, the same maximum pressure as .223 Remington. It was designed for one market: the Midwestern states, Ohio, Michigan, Indiana, Iowa, and others, that allow deer hunting with straight-walled rifle cartridges but not bottlenecked ones. Winchester calls it the fastest SAAMI-approved straight-walled hunting cartridge, and it is: a 150 gr bullet at 2,325 fps from 20″, a 180 gr at 2,100.
The case is a straightened, slightly lengthened .223 case with a .378″ rim, which is the whole trick. It uses a standard 5.56 bolt, a standard upper, and a standard barrel nut; only the barrel and the magazine change. Recoil is about half of a .450 Bushmaster and less than a .243 Winchester, so it is the straight-wall cartridge for a youth hunter or a shooter who does not want to be punished, and at 150 to 180 gr it carries 1,600 to 1,800 ft-lb at the muzzle and stays deer-capable to 200 yards or a little past.
Faxon rifles it at 1:16, the SAAMI-standard twist for the cartridge, which stabilizes everything from the 145 gr FMJ through the 180 gr Power-Point and the 255 gr subsonic. Both barrels run carbine-length gas on a .750″ journal. Winchester publishes its 350 Legend figures from both 16″ and 20″ barrels, so the numbers below are the numbers these barrels make. Read 350 Legend vs. .450 Bushmaster for how it compares to the other straight-wall choice, and the 350 Legend Q&A for the rest.
Winchester factory data — 16″ and 20″ test barrels
| Load | Bullet | From 16″ | From 20″ |
| Winchester Deer Season XP | 150 gr Extreme Point | 2,225 fps / 1,649 ft-lb | 2,325 fps / 1,800 ft-lb |
| Winchester Power-Point | 180 gr Power-Point | 2,000 fps / 1,598 ft-lb | 2,100 fps / 1,762 ft-lb |
| Winchester USA | 145 gr FMJ | 2,250 fps / 1,630 ft-lb | — |
Source: Winchester’s 350 Legend FAQ, which publishes figures by barrel length; the 16″ and 20″ columns match the two Faxon barrels.
Duty Series 350 Legend Barrels
All 1:16 twist, 4150 CMV, QPQ nitride inside and out, 1/2x28 muzzle. Weights are nominal; prices are MSRP.
What You Need to Build It
A standard 5.56 bolt carrier group (the .378″ rim is the same), a mil-spec AR-15 upper, and a standard barrel nut; 350 Legend-specific magazines, which are single-stack-style AR magazines with a follower and feed lips for the straight case. Faxon’s Big Bore upper, with its opened feed ramps and ejection port, is a recommended option that improves feeding and ejection with the straight case. Both barrels take a .750″ gas block on a 1.9″ journal and a carbine-length gas tube. Muzzle is 1/2x28 with a .357″ bore, so it takes only 9mm/.357-bore devices; a 5.56 device will not pass the bullet.
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, so the air-gauged dimensions are the dimensions you get and there is no chrome layer to wear through. Every barrel is shipped with its extension torqued to 150 ft-lb, pinned, and headspaced with a go/no-go gauge, then 100% wet magnetic-particle inspected, finished with an 11° target crown, and 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 350 Legend FAQs
Does 350 Legend need a special bolt?
No. The 350 Legend case has a .378″ rim, the same as 5.56, so a standard 5.56 bolt carrier group works. The magazine is the part that changes: 350 Legend magazines have a follower and feed lips built for the straight case. Faxon’s Big Bore upper is a recommended option, not a requirement, for 350 Legend.
Is 350 Legend legal for deer in straight-wall states?
It was designed for them, and it meets the case-length and diameter rules in Ohio, Michigan, Indiana, Iowa, and most of the other straight-wall states. Regulations differ by state and change; check the current rules where you hunt.
16″ or 20″?
The 16″ is the handier carbine and gives up about 100 fps: 2,225 vs. 2,325 fps with the 150 gr Deer Season XP by Winchester’s figures. The 20″ is the choice for a longer shot across open ground. Both are the same profile, gas system, and twist.
What muzzle devices fit?
Any 1/2x28 device with a .357″ or larger bore: 9mm brakes and flash hiders, and 9mm/.357-rated suppressors. A 5.56 device has a .22-caliber bore and will not pass a 350 Legend 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.
