LOL dude it's called a critical hit!
D00d it's a critical hit, man factors affect it:
#1. Where you shot the person.
#2. You're critical hit chance.
#3. If you have any critical modifying stats (such as better criticals or more criticals).
#4. Your weapon and your chars proficiency with it.
Now I know you know all of the above but the thing is a critical is nearly random damage. Now that that's been said, consider the bursts, firstly every bullet is rolled for when fired (so 40 rolls, if all are critical you get shitload of damage). ALSO keep in mind that both miniguns use different kinds of ammo. Remember that the Vindicator uses 2MM (or maybe it was 50 MM EC, i never use it, ammo is too hard to find). While the Avenger uses 5mm (or is that just the minigun??). ANYWAY to stop deviating from topic, keep in mind that different ammo cause different effects on the damage. That being said, if for example 2 MM did like +50 damage mod, while 5mm did no damage mod (maybe range mod?) the individual bullets would cause far more damage (+50%
Now taking that into consideration, assuming 5MM had a negative mod (ie - Dist or DMG) it would affect the critical (regardless if you're at point blank range or not). Now let's conclude this, first off I'm not sure about the weapons, I do know about criticals and how they are fairly random. But I hope that solved your "why does a weaker gun cause more damage??", and the answer is "Consider the ammo, plus the critical damage, plus the armor class mods, plus the distance, plus the skill" so the answer...
WHO KNOWS? JUST USE IT IF IT'S BETTER!
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