COLT - M4CQB Replacement Barrel Stripped 10.3in

Recieved this barrel 3-26-22. Barrel came in Colt factory box in blue sealed vapor bag. Barrel had good coating of oil on it. Barrel looked to have crome bore and chamber. Barrel came with front sight tower with front sight post installed and front bottom sling swivel. Front sight was not F marked but was F sight height of 1.98 inches . Also had barrel nut. Barrel extension had m4 feed ramps and also had extra cuts that were at a different angle and were done after barrel was parkerized. Only marking on barrel was cage code " 13629 M P 5.56 Nato 1/7". No other marking on barrel. Installed this barrel on Colt lower with GI spring and H2 buffer and m16 bolt. With m4-2000 shells eject at 2:30 - 3:00 without 3:30-4:00. bolt locked back with and without suppressor every time mag was empty. Have fired about 300 rounds runs great.

Somehow I forgot to note that the gas block journal measured .7495 in diameter, which is perfect according to spec. If you want a light weight, premium 10.3" short barrel, carbine length gas system, button rifled, six groove and hard chromed bore, high pressure tested and mag particle inspected, then this is the barrel for you.

My 10.3" barrel (received March 2021) was shipped in a sealed, clear bag, not the traditional rust preventative blue bag Colt is known for. I verified the gas port with several pin gauges; nothing larger than .070 would clear so it has the proper diameter hole. The manganese phosphate on barrel and extension was well done and the hard chrome plating fade-out was correct at the muzzle, as well as inside the extension. The index pin was nice and flat, and it's protrusion measured .088 (which is flush to the extension) and properly below the max .094 allowed by spec. The M4 feed ramps were nice and clean, but not too sharp and no chipped/deformed edges. The muzzle thread length measured .630, dead center of the mil-spec tolerance range (.620 to .640). The barrel is marked with Colt's CAGE code "13629", "M" for the magnetic particle inspection, "P" for the proof/high pressure test, "5.56 NATO" for caliber, and "1/7" for the rifling twist. The chrome vendor is indicated with an "I" over the chamber and the extension is marked with a "4" at the 3 o'clock position as well as a "" at the 9 o'clock location for the extension vendor mark. Overall, this appears to be a high quality Colt short barrel with an excellent hard chrome bore and chamber. Nitride might be a better surface treatment over parkerizing to prevent rust, but it doesn't beat HC for protection against hot gas erosion and bore wear. I just wish I would have bought more than one before they went out of stock!