re: handgun in a vehicle (where permitted by law)
If someone goes so far as to actually break into your car, only a metal lock box will likely deter the theft of a firearm.
OR a strong cable that will require bolt cutters (not your typical auto theft tools)
Advanced auto theft prevention devices help prevent the theft of the whole car.
Disguising a handgun is, probably, the next best tactic.
- darkest legal tint, dark upholstery and blending cover
Stainless eye bolt, cable, and cover (AK folder also fits in a tennis racket case)
Dark tint, black interior, handgun holster and matching cover