Back when I had access to a large place in the middle of nowhere I'd make my own, even blew up few beaver dams sky high with a high power rifle from a safe distance. It's way cheaper. It's easy to make, and if you are not smart it's easy to hurt yourself. If making your own for pellet rifles, you have to play with perchlorates. I did some but mostly stuck with the easier and safer pure pottasium nitrate, 3 micron aluminum, and tiny bit of sensitizer(acid free sulphur). Bigger booms with ammonium nitrate for high power rifle stuff instead of pottasium nitrate, but it is hard to get any volume of ammonium nitrate at a decent price unless you know a friendly farmer that doesn't mind your hobby and is willing to sell you a 50lb bag, mine retired 15 years ago but it's been 12 years since I had access to a place I would use it anyway and hadn't used up my supply when I lost my source. Good luck finding a farm supply place that will sell ammonium nitrate fertilizer to you unless you are a known farmer, and of course there is the required paperwork they keep on file for the alphabet agencies if you did find a place.
