[cpl tank]

The carbine gas port is located closer to the chamber than the gas port of the M16: 7.5 inches instead of the 13 inch distance on the M16. The gas pulse therefore enters the gas tube sooner and reaches the carrier group earlier than it does in the M16 length barrel. In addition to reaching the carrier sooner, it reaches it at higher pressure. The gas pressure at the carbine’s gas port is double that of the M16: 26,000 psi vs. 13,000 pounds per square inch.

[Billthedrill]

Holy crap! No wonder there are problems. Many thanks for digging that information up for me, I wasn't having much luck and my Army contacts are out of town at the moment...way, way out of town...