I have to say that having a low-strength container means the pressure does not build high. The force of an explosion depends a lot on having chemicals that erupt rapidly together with a container that holds to bursting from high pressure then breaks apart with great momentum and a massive shock wave. An explosion in cardboard would be very weak actually. I can't talk online about how to derail a train but I know that mere fireworks level of bomb would not be adequate.

I know from fireworks making that slow combustion is weak, poor containers are weak. Fireworks mostly uses cardboard tubes and is designed not to blow things up but to 'pop'. Military explosives are designed to bang with a high velocity shock wave.

I have to say that having a low-strength container means the pressure does not build high. The force of an explosion depends a lot on having chemicals that erupt rapidly together with a container that holds to bursting from high pressure then breaks apart with great momentum and a massive shock wave. An explosion in cardboard would be very weak actually. I can't talk online about how to derail a train but I know that mere fireworks level of bomb would not be adequate.