Still, you have to work with what you have. Sadly for us, Tier IX has the worst grind.
I didn't have the 130mm on the WZ-111 for like 91 battles, but still I managed to keep the 100mm working with an average damage of 1500, which isn't great but it's there, almost the tank's HP. It's rather simple, you must find a way to get your gun working and putting effective shots on your enemy, remember that the more damage you do, the bigger the chances to win are.