I understand a lot of people weren't a fan of the "called shot to ignore armor" rule in 4th, and RG5 is prettymuch the same... Makes me wonder a bit.
The big difference is RG5 is not for called shots, it is being applied to all shots/attacks with the idea that the chance for you attack of succeeding is now being reduced by the armor and your only really doing damage by getting around the armor/blowing through it. Sort of like the old AR system in palladium where you had to roll your attack higher than the AR to damage. Anything else was treated as hitting the armor and not penetrating.
Now this does not mean everytime you do succeed you hit a gap, you may also have blown through the armorey bits, but again the heavier/more covering the armor the less chance of succeeding.
Also remember, under GR5 armor does not convert P damage to S damage, so the shots are either being stopped by the armor or your bleeding from successful hits/penetration. So passing out from a filled stun track is not much a concern now and a lot of possible damage is going to just flatten against the armor.
And that is where there is still some questions on the math as an armor jacket is going to reduce that attack dice pool by 12 minus whatever AP you can muster. So if you got 5 Agil and 5 Pistols with a weapon sporting a -2 AP, your initial attack DP of 10 gets zeroed out by the armor mod of -10 (12 armor reduced by the -2 AP to a penalty of 10), unless you toss in edge or use centering for adepts like Rhat suggested, or get a higher AP weapon or ammo. APDS is going to be popular...
Still bouncing numbers, but it almost seems like they used old SR4 values for armor when the math was made , but again since damage is going to be P more you want less to get through so the higher armor values of 5th may make sense, but mooks are going to be flattening a lot of ammo against even moderate armor, so maybe that was the idea for more cinematic guns blazing style.