as always, when u don't know what is he talking about look at tags. In most cases tag is this ENTITY/THING. I only know how it worked with ogris in update 12, it made projectile pass through enemies without harming them(projectile didn't have on-hit damage, only explosion) so 1-2 maybe 3 enemies were "tresspassed" on the next one or on any surface projectile exploded. With groups better, cuz exploding INSIDE this group, dealing damage to more enemies, with lone enemies very annoying, cuz projectile pass through enemy, and go further, enemy alive and still moving:weapon NOT eeffective.Dunno how it works now, it should deal damage from impact to enemies penetrated, after end of punch through it should explode dealing damage normally. Someone should test it and confirm or decline.
Other thing to keep in mind is that the Ogris (not sure of other weapons) will have the missile pass into an object instead of proc'ing the explosion on impact. This can be very annoying when shooting near the feet of an enemy, or setting up shots to take out enemies behind cover.
I use punch thru on my penta, never suicide again :) it never bounces back to my face initial hits deal dmg and penetrate. same with ogris, projectile has puncture dmg? Penta has impact dmg on the projectile.
I'm certain that both the Ogris and Penta are compatible with punch through, though they they can have some downsides. The upside is that allies can't body-block your projectiles and kill you, but the downside is that Ogris missles won't detonate in a normal manner, and Penta grenades may end up going through the floor and leaving you behind (if I remember correctly). Stug might work, but I'd expect some whacky results if it does. If Torid does as well, the projectiles may end up embedded in the ground and have the gas clouds rendered less effective, so I see no purpose in using it.