Do you value your health? I would be concerned about “spontaneous unscheduled disassembly”. Those guns probably are not engineered with a margin of safety to withstand the pressures of diesel-type internal combustion; they simply were not designed for that. It could be an interesting idea for a purpose-built gun though.
You are right, not worth it. Amerex just did a tune up on it for me a few months back. I think 1170 fps does the job fine. Thanks for responding.