The G5 can be used with barrels 10.5 inches and longer. Full auto is not a problem as long as a little common sense is used. After 2 (or at the most 3) magazines, the weapon system should be allowed to cool. This is true for the basic firearm as well as the suppressor. The issue is not so much one of the suppressor, but it is more one of the ammunition. Remember, the heat of friction and powder burn raise the bore temperature to well over the melting point of lead in less than 3 magazines, soon after which time the small mass of lead in the core (surrounded by a large surface area of heat conductive copper jacket) starts to soften/melt and destabilize the bullet. This results in baffle strikes, which is not warranted. The suppressor will tolerate extreme heat; the ammunition won't.
I am not a fan of short barrels for this cartridge, which was designed for a 20" barrel. While they may look cool, lethality diminishes rapidly with decreasing barrel length below 14.5 inches, and at 10 inches there is inadequate velocity to make a decent wound channel, resulting in simply drilling a 1/4 inch hole through the target without doing a lot of damage. Symbolism over substance: a characteristic common to too many thought processes today.