Consider that leaving behind even brass is a way to be traced, unless you scrubbed each shell with gasoline or bleach, or whatever your preferred agent is (gas probably not so much). When they were testing the AK-47 out initially they were instructed to pick up every bit of brass so the project wouldn't be leaked. Now mags are allot more specific, and if somehow you don't have footage or something similar you've got something hard to go off of from a number of different angles.
As far as it taking that much extra time to keep it all together, it shouldn't but, as you stated earlier JN the action phase is at the very least full of quantum anomalies. I think they should shrink how much time an Action is from 3 seconds to one to better reflect un-augmented human capability.
Caseless ammunition is much more common in 2070 than cased - Revolvers still use brass, but they don't spit it out.
I would strongly recommend
against scrubbing your rounds with gasoline or bleach. Or any liquid, but certainly not gasoline or bleach. You don't want solvents, especially flammable solvents near your ammo.
Best case scenario, they gunk up the powder or the firing mechanism.
Worst case scenario?
Think this through. You want to scrub you bullets with gasoline, stack them up in a magazine, then load them into a firearm. They're called "firearms"
because of all the fire.When the gun fires, exploding flaming hot gasses push the bullet down the barrel. They also cycle the chamber open on top of your magazine, so there's one potentially bad situation, as your entire magazine catches on fire.
These explosions also make the chamber very hot, so if you feed the next round in, and you have a second scenario for unwanted flaming explosives going on in your weapon.
Use caseless. Wear gloves. Don't have a SIN or Records On File. (Everybody's worried about prints...most Shadowrunners aren't in the system to begin with.)
-Jn-
Ifriti Sophist