Well, the guns of SR, are not the guns of today, that much is very clear.
All firearms in SR use caseless ammo - something that was researched and abandoned by 1993 for us.
Also, technological creep is probably also a factor. Take your phone for example; why is a device that you are supposed to speak into capable of surfing the internet, playing full length videos, play games, record full length video (or millions of pictures), report your location, and help you navigate a city!?!? ITS A FUCKIN PHONE!!! - YOU TALK INTO IT!!! Firearms in SR probably could order, and and make you a cup of soy-caf with all the extra shit they have put into it...
(I can just see it now... the Runner, slinking through the hallway, approaching the guard station, pulls his pistol.
GUN: "Good evening Mr. Smith. It is currently 73 degrees outside, with a humidity factor of 4%. Rain Expected at 7am -Pack a umbrella. Lightning levels low, activating low light sights, and gun flashlight - no need to thank me. You currently have APDS ammo loaded, adjusting sights to compensate for propellant load and projectile weight. Please, Don't forget to update to Firmware patch 45.23a At your earliest convenience. Thank you for Shopping Ares!
Runner: "Fuck... forgot to put it in silent mode..."
Guard: "Yep... And don't worry about that Firmware update. Its crap." *BANG!*)
Anyhow, thanks to the caseless ammo, it could be argued that the current firearms use a electronic spark to fire the round instead of a percussion explosion now, and that is the very thing that gets "bricked" when the gun is bricked... you can pull that trigger all day long, but no spark, no ingition of the propellant, no shooty stuff.
But really, at the end of the day, it boils down to an attempt to make the Decker archtype a little more viable by not only giving him something matrix-y to do during combat, but also helps de-pioritize direct combat skills for the decker. A big complaint for deckers has always been skill bloat and "you can't make an effective decker and an effective combatant"... well now you don't have to, and still have an effect on combat.
So really, this becomes mute pretty fast if you don't have a decker on your team... as event the most proficient NPC decker isn't going to to be able to do much that changes the outcome... Yea he bricks a gun - which you use to beat him to death with. Then spend an hour with a electronics kit to get your gun working again... And really, who doesn't carry a spare gun?
Or four...