@BaldWraithSimp this is interesting because I was curious to see what penetrates and when, and what doesn't.
Unsurprisingly, all main ammo weapons don't penetrate.
PK and Prowler (CP weapons) don't either. Did you know the Kraber doesn't always penetrate either? In the firing range, shooting a test dummy from an angle (lining up with one of the flat pop-up targets) won't always penetrate the test dummy and hit the pop up target behind it. This is both for headshots, and bodyshots. Upon further testing, it seems hitting enemies near the face area will cause penetration, but hitting more towards the top of their head will not, but it still doesn't always penetrate. I tested this again while facing the dummy from the front, and the same behavior occurred. Maybe the Firing Range is bugged.
Shotgun pellets won't penetrate on kill, nor hitting the body. In fact, damage from pellets that exceed target health simply disappear upon hitting an enemy.
All floor loot snipers follow the same pattern as the Kraber, with some shots occasionally penetrating, and others not. Sentinel charged shots and normal shots don't always penetrate for both body and headshots, same with Skull Piercer Longbow. Surprisingly, Triple Take does penetrate targets. Also surprisingly, Charge Rifle hip-fire is really "accurate", as long as you keep the little dot in the center, you'll always hit for at least 45 damage.
What's annoying though, is the lack of genuine penetration through thin cover. Railings, sheet metal, small poles, etc. etc. It'd be nice to have bullet penetration for all weapons (albeit with reduced damage), with each specialty ammo type having different properties while firing through thin objects.