What Are the Differences Between Gun Propellant and High Explosives?

[lemd]

I read that gun use height pressure gas to push the the projectile
And the speed of explosion is limit at ~ 3km/s
And I read that in a shaped charge explosion, the jet can travel faster than 7km/s easily

Can anyone tell me what is the different between these two explosion?
What the speed of explosion depend on?
Why in a shaped charge they only use normal chemical but the speed is too height than normal?
Why don't they use shaped charge as propellant for gun?
Is the velocity of detonation mean the speed of blast waves of explosion?

My speciality is not much relate to physics but Id like to know, I tried google a lot but it isn't effected, so please help me

Anyway, thank for reading

 

[Astronuc]

The chemical charge used to propel a shell in artillery or bullet in a gun is a low explosive with a relatively low detonation velocity. In contrast, a shaped charge often uses a high explosive with a high detonation velocity.

If one where to use a high explosive to propel a shell, then the gun would likely explode, which would be counterproductive to the purpose of the gun.

 

[Bystander]

The deflagration rates of ballistic propellants are measured in m/s, and the reaction front is propagated by thermal excitation; the detonation rates of explosives are measured in km/s, and the reaction front is propagated by the shock wave associated with the detonation.

 

[Astronuc]

In general, propellant charges have the oxidant and fuel as separate components which are mixed. The high explosive have the oxidant (ONO₂ group) as part of the molecule, e.g. TNT, RDX or HMX.