I used the PSI bolt pen top and tube along with a parts from a cigar. The projectile is a Barnes 150 gr which I drilled out like the PSI nib on the kit. I used the cigar coupler and turned off the flange. I then drill out the brass casing to the size of the coupler and soldered it in. I then took the cigar transmission and removed just the threads. I used other size tubes to build out the cigar thread tube to fit inside the bolt tube. The threads have to be recessed from the end. I epoxied the threads in and soldered the other tubes together. I then cut the tube to the correct length. and put on the antler. The pen length is 5 1/4 inch. It was a lot of fun. I am not sure but I don't think I have ever seen one like this on the forum. If anybody has more questions just ask I will be happy to help. Rich