Exploding Cannon Rounds

[BreakingBad]

I've always wondered how 20 and 30 mm cannon rounds are designed to explode.

It would seem that the firing of the round in itself would cause enough rapid acceleration to explode the round.  I guess it is the rapid deceleration of the round hitting the target or deformation of the round that causes the explosive to go off.

Also seems like the the volume of explosive that could be fit inside of the round would be so small in order to keep the integrity of the projectile itself as to make it a nominal explosion.

Obviously they work and were widely adopted so I suppose the point is moot.

[Seanaldinho]

I've always wondered how 20 and 30 mm cannon rounds are designed to explode.

It would seem that the firing of the round in itself would cause enough rapid acceleration to explode the round.  I guess it is the rapid deceleration of the round hitting the target or deformation of the round that causes the explosive to go off.

Also seems like the the volume of explosive that could be fit inside of the round would be so small in order to keep the integrity of the projectile itself as to make it a nominal explosion.

Obviously they work and were widely adopted so I suppose the point is moot.

It largely has to do with the actual jacket of the round. Full metal jacket rounds are armor piercing as the round is not designed to fragment on impact. High explosive rounds fragment more.

[Reschke]

From what I remember they are simple impact fuses and yes sometimes they don't blow up on impact but if no obstructions in the barrel then there is no trouble with them going downrange and blowing up in the barrel.

[gyrene81]

here is a decent illustration of how the mg 151/20 20mm explosive shell worked...

[titanic3]

Some had a time fused so they exploded a few milliseconds after penetrating the armor/plane. MK103/108s had the equivalent explosives of a German stick grenade.

[GScholz]

The German round pictured was quite an advanced piece of micro-mechanics. It had a spin activated contact fuse so it wouldn't blow up in the barrel, and a spin/transfugal self destruct fuse that also acted as a backup for the contact fuse. In other words the shell wouldn't be able to detonate unless it had traveled some distance from the gun, and the shell self destructed after traveling 900 - 1400 meters depending on fuse type. If the contact fuse fails the slowing of rotation from passing trough the aircraft structure would set off the self destruct fuse.