I’m not so sure about that. Since in my game, when Reaper had as little as 5% health remaining, it did not start the self-destruct.
this is only something you will find out when you use garbage weapons against the reaper, ive asked even carni to update the wiki page for it, if you use the pvg or the kvm for exsample on lower difficulty than guerilla you can speedkill the reaper before it wants to kys but yes this is the starting point of the suicide mode
I’d need to see Reaper HP bar at the start and at count down sequence to determine it’s HP % to confirm it’s 15%. Does seem high to be fair
Self-destruct?? Who knew? (Not me, that’s for sure.)
This explains that time where one dropped only 3 or 4 ammo items.
But, as far as multiple experimentals? Never happened. One at most, sometimes zero.
This is on Skirmish, not Guerilla. Does that make a difference?
Is the Reaper the only one that does that? What are the warning signs?
No. There is no differece to loot pool between difficulty levels (though, there could be, where higher difficulty = better/more loot).
Yes.
For a warning sign, Reaper starts exhausting red smoke. Though, don’t confuse it with the green smoke, which is prequel to the Thermoboaric attack.
E.g in my gameplay video, at 22:25, you can see the red aura/smoke around it (when area around Reaper is illuminated for split seconds):
Though, that red aura/smoke is so subtle that i didn’t notice it at all. Since then, i’ve fought with Reaper 2 more times and still i don’t spot the red smoke, indicating it’s self-destruct sequence. 
Thanks! Very helpful.
- s.west