Hi Mick, in order to burn 🔥 off the excess oil from the neatsfoot soaked piston seal, you could save money on pellets by firing them into an old cushion or pillow or thick foam sponge* which should absorb them without deforming them… combine that with a bit of target practice at 30 yards or so and it won’t seem such a waste of time!
Guid luck with your project.
A’ the best Mick, Graeme 😎

* Money saving methods collated by the Aberdeen-Yorkshire coalition of Tight Arses ( The Deep Pockets- Short Arms Society) 🥴