Keith - burning fiercely = loss of turret; explosion = loss of ship. It didn't only happen in action, ships were lost by accidental explosion, such as HMS Vanguard, the French Liberte, USS Maine.

RN cordite was not only more like to ignite because of the method of storage (silk bags only) but more likely to explode rather than burn.
A propellant (powder in US parlance) is mixture of nitrocellulose and nitroglycerin with a stabiliser and plasticiser. The difference between an explosion and burning is pretty academic, a matter of micro seconds. And I'm certainly no physicist.