Flak Gun Alternatives

I wanted to create Flak for one of my custom missions. I chose the Flak 36 as I thought it would come with time-fuse shells. I tested it and it seems the shells only explode once a maximum distance has been reached, as they all kept exploding above my aircraft, to further test it out, I got real close in to one to see if they would change the time fuse but it was the same, the shell flew right past me and detonated way behind me. I know there are guns that can change fuses, I’ve seen it in Gaijin official maps. If anyone knows how I can get a gun working like that with an actual variable fuse, that would be great. Thanks!