Overheat, Rapid Fire and Ammo Dump

[cleveland]

How does the Ammo Dump work with Rapid Fire and Overheat?
Example: Can I reroll the 1's before the negative effect happens?
It has been argued by my opponent "Because these are special abilities with a negative effect that have nothing to do with a plentiful ammo supply", I may not reroll those 1's.

Rapid Fire - In your assault phase this unit can make an additional attack. If this unit rolls any 1's during the additional attack, put a face up disrupted counter on it. This counter isn't removed at the beginning of the next casualty phase.

Overheat - If this unit rolls three or more 1's on a single attack, put a face up disrupted counter on it. This counter isn't removed at the beginning of the next casualty phase.

Plentiful Ammo - After each friendly Soldier or Vehicle attacks, you may reroll any 1's from its attack dice roll. (You may only reroll an attack die once with this ability.)

This game is currently "on hold" so I would greatly appreciate some unbiased insight regarding this matter. I am playing China vs. Japan and specifically refering to the Kuomintang Machine-Gun Team and Brixia M35 45mm Mortars (according to Der Leiter, historically chinese armies did/can use the mortars).

[Der Leiter]

"...Because these are special abilities with a negative effect that have nothing to do with a plentiful ammo supply", I may not reroll those 1's."

You get the re-rolls from Plentiful Ammo first, then look at the dice. If you had plentiful ammo and Guards crew from a T-34/85, you would get to chose which of the two abilities you used first, then use the second. After all that's done you can then look at the results for your overheat, rapid fire, flamethrower, etc.