I'm trying to google what happens if you shot a gun to other firearm and found no result

[cody lundin]

If an incendary bullet penetrates over magazine would cause explosion spreading bullets to any direction like fragmentation grenade, this is very possible, I'm not sure about standard bullet.

no, a phosphorous tracer round would cause a few more accidental discharges bit if you want a full discharge youll need to land dead on accurate with an RPG