[Mirikon]

(this device IS called suppressor, damnit! Sorry, that's a pet peeve of mine).

I believe this falls under the precedent of the Clip v. Magazine case law...

[Lucean]

I used to use alot of flechette ammo back when I had a character who had a thing for headshots. unless they were wearing a helmet or something to that effect, it would waste them pretty quickly.

Ignoring Armor might be nice if you have surprise, but a dicepool penalty equal to armor modified by AP is too much, if the target can defend and has at least a bit of armor in SR5.

[SnowDragon]

I think the hope is that you up the damage by so much that the extra dice they get to resist with isn't enough. I mean, once you've hit, you apply the entire damage code +net hits. An old 4E Door breacher I had with a spas-22 in burst fire once laid like 19P once the flashbangs went off onto a guy. It didn't matter what armour he had on or what benefits the ammo gave him, he was paste no matter what. There's just no way to clear that much damage unless you're the holy lord and roll entirely hits on the resist

[Lucean]

So around six net hits, that's much. But be careful, as you can't choose by default between wide and narrow bursts anymore.
There are currently two narrow burst options, one for three bullets (Aimed Burst) and one for six bullets (Brain Blaster). Both require a complex action to use. Aimed burst is to be used with BF mode and Brain Blaster with FA. They increase the DV of the attack by 1 (Aimed Burst) or 2 (Brain Blaster). So you're often better off with using standard wide bursts and reduce their defense pool, because you still have another simple action.

[SnowDragon]

And impact armour was almost always lower (or substainally lower in the case of form fitting) than ballistic, which added salt to the wound. Effectively, while Flechette would give them a +5 to resist, it was more likely to be a +3 or worse effectively depending on the  difference in ballistic and impact armour on the subject, which that much of a boost when you consider it in the grand scheme of things. And since this a 4E or before thread, heck, imagine the carnage you could lay down with an AA-16 + Flechettes.