Fixed-forward weapons require multiple low-angle staring runs to project sufficient throw-weight. The time between runs lets the bad guys regroup and reposition to increase their defensibility. .338 is a good sniping round, but close air support / close combat attack is all about throw-weight. 100 x 7.62 per second is pretty convincing to the bad guys to at least keep their heads down for an extended period. Add 20 x .50/sec and they’re paying attention. CH-146 CCA in AFG was pretty darned effective, especially when you orbit above The baddies like a mini-AC-130 gun-ship and can put down continuous fire...actually much more effective going through tin roofs of grape huts than LAVs pounding away with 20mm trying to break through 2-3’ of sun-cooked mud walls.
The 429? It has half the payload of the Griffon and by the time you load it up, it will have lost any speed advantage over the Griffon. It’s time in target for weapons/ammo load out would be less than the Griffon.