Review on Spanner Nut Wrench: Ultimate Tool for Locknut Removal, Tightening & Pipe Fitting by Derick Johns

Not sure what other reviews that mention damage to threads or castellated nut are talking about. I put on some mechanical gloves and slowly adjusted the wrench to find the best grip. I had a good grip, my castellated nut was tightened to my satisfaction within minutes with no slipping or damage to the threads or castellated nut. I've seen how someone can slip and damage or scratch their buffer tube or threads if they're hasty, careless or careless. However, I had no problems. Take your time, don't blame the tool for a lack of patience when you scratch your rifle.