I have a 46C. The back piece of the bolt is threaded on, standard RH thread. I had to soak mine in Kroil for an afternoon to get it loose. Some heat might help. Hold the bolt assembly in a padded vise, unscrew the front half. It is under spring pressure so getting it started again without cross threading can be tricky. Here is the thread I had on RimfireCentral. http://www.rimfirecentral.com/forums/showthread.php?t=871058&highlight=