Currently fixed forward firing miniguns on helicopters (AH-9 Pawnee and PO-30 Orca) are quite useless as taking down even a single stationary man, standing in the open, is next to impossible. I usually just go reload after firing the rockets even if there is still infantry and other soft targets around.
I believe that the biggest problem is the extremely tight grouping of the miniguns: even at the range of 800m the groups of the two separate miniguns of Pawnee are not mixing with each other. Because of this, shooting at practical helicopter combat ranges in ARMA (300-500m) is very ineffective due to the bullets landing on two exact spots on both sides of the crosshair. I would suggest increasing the spread to something like 1,2 meter spread per 200 meters of range, this way the bullets would cover the center of the crosshair at the most common helicopter combat ranges.
Another issue that bogs the power of fixed miniguns is their low rate of fire. Rof of the fixed miniguns in ARMA3 (in both AH-9 and PO-30) is 1800 rounds per minute per gun, it's a low setting for any M134 and extremely low for an aircraft mounted one. Even if you manage to walk the tight minigun group over the target, no bullets often hit due to this. I'd suggest increasing the rate of fire of Pawnee miniguns to something like 3000 rpm per gun and for PO-30's single gatling gun 4000 rpm.
I believe these two changes together would make using fixed helicopter miniguns a real option rather than a theoretical possibility, without making these choppas overpowered or unrealistic.
