I'm working on a military sf game, and I'm running into some hurdles with Flak Cannon samples. I can hear that thudding, puffing mortar-like sound in my head, but I'm not quite sure how to achieve that. I've been processing bullets and mixing them with fireworks, cannons, and base kicks, but it's not there yet. I say abstract sources because I don't have a budget to record actual military weapons. I would also like to avoid purchasing 3rd party libraries. Any thoughts or experiences with this sound design technique most welcome! Thank you everyone.