Actually one of the only ways to do a really fine detail stencil is silkscreening.
Probably easier than doing it yourself, you could just print the logo (size you want) on a transparent overlay and get a silkscreening place to set up the screen for you. You can get it made in an extremely fine mesh for small logos/high details.
Then you just place the screen on the surface you want to paint, apply your paint, remove the screen and let dry.
Never did it for guns, but I had to help someone do it for a small batch of CDs once. Works quite nicely.
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