10mm Auto, By the Numbers
10mm Auto was Jeff Cooper’s idea, brought to market in 1983 by Dornaus & Dixon with Norma for the Bren Ten pistol, adopted by the FBI in 1989, and then largely abandoned by law enforcement for the .40 S&W it spawned. It came back as a hunting and backcountry cartridge, and it deserves to: a .400″ bullet from 155 to 220 gr at a SAAMI maximum of 37,500 psi, 1,200 to 1,300 fps from a 5″ pistol with 180 gr, and considerably more from a carbine.
How much more depends on the load, but a full-power 180 gr load picks up 150 to 250 fps between a 5″ pistol and a 16″ barrel, which puts it around 1,400 to 1,500 fps and 780 to 900 ft-lb; a 200 gr hard-cast hunting load runs about 1,300 to 1,400 fps. That is .357 Magnum carbine territory with a heavier, wider bullet, which is why 10mm PCCs are used for hogs, deer, and black bear inside 100 yards, bear defense in camp, and home defense with a 15-round Glock 20 magazine. Hornady publishes its 180 gr XTP at 1,275 fps from a 5″ test barrel; the carbine figures above are estimates from that.
Faxon builds both barrels on the Light Tapered blowback contour: a 1.000″ receiver journal with an indexing pin, a .980″ collar, a short 15° taper, and a straight .750″ body to a 5/8x24 muzzle. The chamber is SAAMI 10mm Auto cut to a GO gauge; the twist is 1:16, 6-groove, which stabilizes 155 through 220 gr bullets. Because the gun is blowback, hot ammunition is a bolt question, not a barrel question: Faxon’s 10mm PCC bolt carrier has a removable weight so the gun can be tuned to the load.
Manufacturer-published factory data — pistol test barrels
| Load | Bullet | Muzzle velocity | Muzzle energy | Test barrel |
| Hornady Custom | 180 gr XTP | 1,275 fps | 650 ft-lb | 5″ |
| Federal Train + Protect | 180 gr VHP | 1,175 fps | 552 ft-lb | not stated |
| Underwood | 200 gr hard cast FN | 1,250 fps | 694 ft-lb | not stated |
Sources: Hornady, Federal, and Underwood product pages. From a 10.5″ barrel expect roughly 100–200 fps more than the pistol figures and from 16″ roughly 150–250 fps more, load-dependent; estimates, not Faxon chronograph figures.
Duty Series 10mm Auto Barrels
All 1:16 twist, 4150 CMV, QPQ nitride inside and out, 5/8x24 muzzle. Weights are nominal; prices are MSRP.
What You Need to Build It
Faxon’s 10mm blowback bolt carrier group (a 5.56 or 9mm carrier will not work), a Glock® 20-pattern 10mm/.45 PCC lower with Glock 20 magazines (9mm Glock-pattern lowers will not take them), a mil-spec AR-15 upper, and a heavy buffer; the barrel seats on its 1.000″ journal and indexing pin with a standard barrel nut. No gas block or gas tube; any free-float handguard fits. The muzzle is 5/8x24 with a .400″ bore, so it takes 10mm/.40 devices or a .40- or .45-rated suppressor; a .30-cal or 9mm 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, 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 gets its indexing pin and is headspaced to a 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 10mm Auto FAQs
What bolt carrier and lower does a 10mm AR need?
A 10mm blowback bolt carrier group, Glock-pattern and full-mass; Faxon’s was built alongside these barrels with a removable weight for tuning. The lower must be a 10mm/.45 PCC lower cut for Glock 20-pattern magazines, which are wider than 9mm Glock magazines and will not fit a 9mm lower.
Will it run full-power 10mm?
Yes. The chamber is SAAMI 10mm Auto, cut to a GO gauge on every barrel, and the barrel runs everything from 155 gr competition loads to 220 gr hard-cast hunting loads at full pressure. What changes with hot ammunition is the bolt, not the barrel: heavy loads want the full carrier weight and a heavy buffer, light loads may want the weight removed.
How much does a carbine barrel add?
Roughly 150 to 250 fps over a 5″ pistol with a full-power 180 gr load, so about 1,400 to 1,500 fps from 16″ and 50 fps or so less from 10.5″. A pistol cartridge is nearly burned out by 10.5″, which is why the two barrels are so close.
Can I suppress a 10mm PCC?
Yes, with a .40- or .45-rated can on the 5/8x24 muzzle, direct-thread or on a HUB adapter. 10mm has no common subsonic factory loads, so a suppressed 10mm is quieter, not quiet, and a blowback gun runs dirtier suppressed than a gas gun.
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.
