That method totally works, but keep one important thing in mind for a D-Day map. If you have multiple machine gun nests firing that fast, all those arrows getting stuck in blocks will tank the player's FPS and cause terrible lag. Make sure you set up another repeating command block nearby to clear out the misses. You can use something like /execute as @e[type=arrow] if data entity @s {inGround:1b} run kill @s to instantly delete arrows once they hit the ground or the bunker walls, which will keep your world's TPS stable.
