I am not an expert on the Straight Line, but have done extensive research about them the past few months since buying mine at the Symposium. Have not seen a diagram or disassembly instructions.
There is really not much out there on these guns I can find. I have reached out to some of the old guard for information without success. Information dies with the advanced collectors who do not share their knowledge.
Best I could suggest would be to examine the patent drawings. Search online for the patent - if you can’t find it, I can get the exact number for you.
One warning: I did read an account posted here somewhere where someone took one apart and had a tough time with reassembly.
Sorry I can’t help more. Please share anything you learn with the rest of us.