Util.decal for custom grenade


I am working on my first offensive SWEP and I have run into a small speedbump with it.
The SWEP’s altfire launches a custom grenade that explodes on impact, utilizing a different effect than env_explosion.

I want the grenade to leave behind a scorchmark decal when it explodes on whichever surface it hit, but I cannot seem to get the decal to spawn when doing so.

Is there something I am doing wrong or perhaps a better way to achieve this?

Thank you for your time for anyone who reads this.


EDIT: The model for the grenade itself is a sodacan, if you need to know the size of it.