Um, kinda like, nevermind. It was my fault.
This was a very simple program, maybe 30 lines or so, so I figured I'd just Notepad it by hand and not bother with the CAM software. The code was mostly right, it's just that I kinda forgot that I needed line numbers. So I guess Mach3 read the whole thing in as one long command. The last feedrate in the program was 7.5, so that's what it used. Crap.