Custom built to our specifications. .875" before the gas block, .750 at the gas block, then .725 to the muzzle. Black phosphate finished, fluted, 16" long, with mid-length gas, .081" gas port, 1 in 9 twist, with M4 ramps and 5.56 NATO chambered. We like the 16" barrel because it's short enough with a comp attached, to be quick and maneuverable in house clearing stages or close, tight quarters and shooting positions, yet long enough to give the velocity needed to flash steel targets at long range. Fluting both before and after the gas block facilitates cooling and reduces weight. The mid-length gas system softens the recoil impulse over a standard carbine length gas system; and the chamber and 1 in 9 twist rate allows shooters to use standard XM193 or other readily available 55 gr. ball ammunition.
Note: barrels should be installed by a competent gunsmith and checked for proper headspace. Failure to do so can result in firearm damage, personal injury, or death.
Here's a couple of three shot groups we fired with 55 gr. ammo at 100 yards, and is representative of the performance you can expect:
PMC Bronze 55 grain
This particular barrel only had about 50 rounds through it when we fired those groups, so we expect a little better accuracy after the barrel has had a few more rounds through it.
Here's Katie Francis and a .5275" three shot group at 300 yards she fired with her CPWSA Ultimate Carbine and 77 grain handloads.