Help on finishing gun!

Oiling before epoxying is a bad idea. It will interfere with the mechnical bond between epoxy and wood. You want to sand and wipe the wood free of oils using acetone, and also use compressed air to blow dust out of the wood pores.

If all you are after is a wet, dark, shiny look, the epoxy alone will provide that, and provide far better sealing from the elements than the oil ever could.

If you don't have the patience to get a perfect epoxy finish (it's somewhat challenging), you could always just go for the oil. However, I don't know how sapele takes to oiling, or what its natural durability is. Even if it is durable like teak or padauk, if you get any scratches in it, it will take sanding to get the surface smooth and attractive again. And that's wood you can't replace, whereas a thick, multi-coat epoxy finish can be replaced. A thicker finish will also let you wet sand with high grit sandpaper for smoothness.

Ryddragun is right, oil and epoxy don't mix.

You could use penetrating epoxy for the gun or the track only, it doesn't add thickness.

Quote from 808natural

Thanks for the insight Ryddragyn. The reason why I asked is because the guns I'm making has wood enclosed tracks on them and the ball cutter I used to cut the track are a perfect fit for my shaft. I didn't want to epoxy the track and make the track even smaller to where it's squeezing the shaft. I was thinking oil will be better but I'm not sure!

You could also route the track area with a dovetail bit, fill it with epoxy and graphite, and then cut the track with your ball cutter. Low friction and durable, and you can redo it if you mess the alignment up, or if it ever breaks.