Hi all. Need some help trying to solve a problem. I have a Freedom Ordnance FX9 PCC that came with a KAK blade and buffer tube. The tube has threads that are about 1 3/8 in length. I have since bought an SBA3 and SOB brace that came with an aftermarket tube and the threads are only about 1 inch in length. I’m told this is standard tube thread length and not the 1 3/8? Does anyone know if this is true? Possibly a standard tube won’t work on the FX9. Definitely the rear of the receiver from end to buffer pin is longer on FX9 than AR but everything I read on internet says it takes a standard tube. The tubes I have are too short on threads when add castle nut and retainer plate.