I would use 'rifle enthusiast' or 'rifle specialist' or 'marksmanship disciple' if you want to avoid the hypersensitive tone deaf Karens. I like 'enthusiast' as it connotes positivity and potential.
Decades ago, the gay community adopted the 'queer' epithet and wore it both in defiance of and to take power away from their detractors. Worked for them, though this situation might be a little different. The ignorantii do love to sling that 'gun nut' epithet around though, and that's another term we use ourselves in comic self-deprecation.
