In UDMC’s DGIS Mid-Length System caliber 5.56 NATO, the barrel uses a "mid-length gas tube" of 11.25 inches long. Typically, the standard carbine has a gas tube length of 9.75 inches. This gas tube length of 9.75 inches is the one used for barrels 10.5-inch, 11.5-inch, 14.5-inch up to 16-inches. In the UDMC design, it was decided to lengthen the gas tube, for good reason.
The Mid-Length System uses a mid-length gas tube (11.25 inches) with a “forward” placement of the gas port in the barrel. The drilled gas port is seven (7) inches measured from the tip of the muzzle of the rifle instead of the standard specification of 8.5 inches from the muzzle tip. The effect is that there is less gas pressure being rammed back into the BCG gas key. The DGIS Mid-Length System renders a slightly “softer” shooting AR with slightly less heat flowing back into the bolt and bolt carrier group and other critical parts, key to longer life and a little less maintenance. This system mimics the more efficient and reliable performance of the 20-inch barrel M16A2 while using shorter barrels of 14.5 and 16 inches.
Since UDMC produces its own barrels from cylindrical blanks, it is able to introduce this new S5-DGIS Mid-Length model on 14.5 and 16-inch barrels. Because of this, the gas port can theoretically be drilled in wherever part of the length of the barrel, something that AR assemblers are unable to do.
The DGIS Mid-Length model uses a longer handguard since the standard M4-length handguard is now short. The handguard that is installed is a T6 aluminum “KeyMod” railguard that will float the barrel, a feature that a purist competitive shooter wants as it aids in better accuracy. As another option, the KeyMod railguard can cover or not cover the gas block front sights. If it is preferred that the gas block is inside the railguard, UDMC will install a “low-profile” gas block that will fit inside the railguard. That will also mean a longer railguard to cover the gas block. For the latter design, UDMC will install its own fabricated set of flip-up sights for the front and rear.