I'm generally not a fan of random things, but IMO, ammo explosions and weapon/equipment damage in a MechWarrior game is a good thing.
Taking a risk for that extra salvo/few seconds of speed is a great idea. The further over you go, the higher the chance of things being permanently damaged become. As said by Virt, it is an extra consideration for the pilot to make.
If ammo is given a specific temperature before it goes off, people will just learn to stay just below that point. That is unrealistic and no fun long term.
Taking a risk knowing full well you'll probably die or severely damage components, but managing to pull it off is extra rewarding.