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For starters, a real mount for the M600 series doesn't cost all that much.
What's your M600C worth to you? For that matter, what's your life worth to you if you really need your weapon light to function correctly and not fall off the firearm when you need it most?
Why not just tape it or zip tie it to the firearm and put some foam/tape/plastic on it (between the light and the firearm) if you really want to go cheap. I would save your money for a proper mount and not bother with cheap Chinese crap. Whether it has worked for someone or not in the past is irrelevant, it's still cheap crap and not something you should willing stake your life on.
A SureFire weapon light and a proper mount is one of the things that I don't skimp on. Cheap optics, mounts, and cheap flashlights don't stand up to recoil, abuse, or mother nature.
Seriously, go on eBay and find a SureFire M600 mount for cheap that someone wants to get rid of because they purchased a fancier mount. The thumbscrew mount that comes with the M600 is usable and all you need is a dab of locktite to keep it in place once it's attached to the firearm.
Every attempt I've made at "going cheap" on optics, mounts, and lights has failed, but feel free to learn the lesson for yourself.