COLT - AR-15 Gas Tube Stainless Steel Carbine

Heavy drill marks inside gas tube inlet hole. Heavy burr at bottom of hole, inside tube. Hole should've been reamed after drilling and then deburred. Rough finish is perfect place for gas fouling to accumulate. This tube should've never passed quality control. Returned for refund. Ordered another Colt carbine tube. Will see what happens. This Colt tube was slightly but noticeably heavier than CMMG carbine tube I ordered along with this. Steel grain of this tube was finer than of CMMG tube, showing a higher grade of stainless. Colt tube had inside diameter .110 - .113 compared to CMMG ID of .113 - .117.

Along with this Colt carbine tube I bought a CMMG tube (from Brownells). This report compares the two. COLT TUBE: GAS INLET HOLE BURRED. Light burr around outside of hole. Heavy burr inside hole, at bottom. ROUGH DRILL MARKS INSIDE COLT GAS INLET HOLE. Very rough drill marks in the gas inlet hole. Hole obviously not reamed. Was drilled very fast. Heavy spiral tool mark, 360 degrees worth, on the inside surfaces of this gas inlet hole. WHY BURRS, ROUGH DRILL MARKS INSIDE HOLE ARE NO GOOD. They have the same effect on the barrel gas that putting a rough/coarse surface inside of a motorcycle carburetor intake manifold has on the fuel mixture. The rough surface causes the fuel mixture to violently swirl around to increase vaporization of the fuel mixture before it gets to the combustion chamber. *I don't want the gas from my rifle to be violently swirled around inside the gas tube.* CMMG GAS INLET HOLE: much smoother than Colt. Appears to have been reamed. WEIGHTS. Colt tube slightly heavier by feel than CMMG. Can pick the heavy Colt tube every time with my eyes closed. STEEL GRAIN: Colt tube has a finer grain to the steel than the CMMG tube. The difference in grain is noticeable by eye. I believe then, the Colt steel is tougher than the CMMG steel. INSIDE DIAMETERS AT CARRIER KEY END OF TUBE. MEASURED EVER 90 DEGREES. COLT: .113 - .115. CMMG: .117 - .118 OUTSIDE DIAMETERS. Colt, Big End: .080. Colt, Small End: .070 - .067 CMMG, Big End: .0795 - .079. CMMG, Small End: .070 DISCUSSION. I like the heaver feeling, tighter grain, and smaller tube ID of the Colt over the lighter feeling, coarser grain, and larger tube ID of the CMMG. Going to return the Colt and buy another Colt. Will keep the CMMG to compare against the new Colt tube.