This. Tape it up, put an adjustable wrench on it. You’re not gonna tighten it enough to hurt anything, or you shouldn’tLooks like the nut has flats on it, should be able to use an adjustable on it.
Put some tape on the nut before you snug it up to prevent any scratches.
@Mustang Jon , bring it to Battery Oaks and you'll never recognize it when we're done with it.
If you're not that brave, the other guys have given you some good advice.
Buy the magpul AR15 wrench.
It's the best one I've ever used.