Agreed with Nabob. Nitrocellulose is a propellant, not a high explosive. The more you confine it, the faster it burns but it does not detonate. The percussion cap of a small arms round or of a percussion primer or tube as used in artillery ammo contains a tiny amount of primary detonating composition, eg Mercury Fulminate. Its only purpose is to produce enough flash and flame to ignite the propellant in the small arms round or the gunpowder / burning composition in the artillery primer or tube. Some of the more modern propellants such as in some tank gun ammunition actually contain a proportion of high explosive, however it is desensitised by the more conventional low explosive proportion of the propellant and therefore will not detonate. As I understand it, the high explosive has more energy and therefore contributes to a higher muzzle velocity and flatter trajectory. The trade-off is that if it turns out to be hotter burning, then barrel life will reduce. Around the time I left, .50" ammo was reclassified from Hazard Division (HD) 4 to HD 3, simply because of the amount of propellant, while smaller calibres remained in HD 4.