I'm afraid to use this - Sniper AR 15 Castle Nut Wrenches

Currently oiling the rim of the castle nut in hopes some gets down in the threads as I am afraid using any force with this wrench. If that doesn't work, there's WD40. There's not much of a notch on the nut for this to grip on, but the entire wrench is roughly 1/16" thick, and if I can remove the castle nut with it, I will likely look for a modern replacement for the nut itself. Anyway this is the only wrench I have seen made for this style of castle nut, so I went with it. But I'm hoping the wrench doesn't just snap the next time I try. There wasn't even any padding to the packaging, so I'm surprised the arc at the end survived the trip.