What Do Warframe's Bullets Look Like?: Headcannon

[Drakontis]

Personally, I think Warframe's bullets look something like these rounds here. 
<iframe width="560" height="315" src="https://www.youtube.com/embed/GrGjIHAq-J4" frameborder="0" allowfullscreen></iframe>

The different properties of the bullet applying differing amounts of damage type. The size of the slug piece at the bottom applying more or less amounts of impact damage, the number of trocars giving higher amounts of slash, and the strength of the round as a whole possibly applying more puncture damage because it's able to puncture through without breaking up as easily. Differing the balance of the rounds enables someone to do different types of damage. 

[Eidolon_Slayer]

I'm pretty sure that round you posed procs slash.