Its simple radman. For starters, it would have an incredibly long reload, its basically a cut down and modified Pzg39. So one would have to both muzzle load the grenade, AND load the blank charge. Then, it only has a range of about 150 meters. Then, its rare enough that it would be about as common a pick up kit as a sniper. It would have to be prone only to fire. So no, it would not be spammed at all against tanks. Its advantage over rocket launchers would be same as the AT rifle, no visible trail to see where the shot came from, and more accurate. Disadvantages would be the prone only reload, weaker heat shells, and very slow reload time.