Someone else suggested this somewhere on ECF and I don't remember where so forgive me. I'm not trying to take credit for it but I want to put it out there. I recently got 4 LR 306 attys from Isaac. They would not thread into my Provari or my REO Grand. They would thread about half way but would not make contact to fire. I took a suggestion from this forum and took some 800 grit sand paper and wrapped the threads in it and twisted 4 or 5 times to round the threads down a little. I then checked it in my REO and Provari. What do you know? They threaded in and made contact now I can use them in my PVs. I informed Isaac of the solution that I had tried and learned from in this forum, and maybe if this helps some of you having problems, I'll have made someone's day a little better. Just passing some info like so many of you who have been so kind as to help me in my vaping adventures.