"Why can't we have control of the indirect fire like on the priest?"

The M8a1 already has the barrage ability (do you mean this ability?) and the M4 105 doesn't have the range for it.

it was made to do both the m4 105 and both of them had the same range as they conter part did look it up and the m10 had the 105 to that did the same

the m4 105 does have the range it is the same as the tow 105 howz