Explosive Burst is one of the choices for the last upgrade for Incendiary Ammo.

It's description is:

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> Ignite enemies with an intermittent explosion that covers 2.50 meters for 135 damage.
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Exactly how often does this explosion happen, and is it a 2.50 meter radius, or 2.50 meter diameter?

The reason I ask is because I'm having trouble with whether this will be worth giving up a whopping extra 12.5% damage.