Why do I sometimes get mini-crits instead of normal crits while Demo-knighting?

[blurFF]

So, for a while now I've been playing a lot of demo-knight. But sometimes when I charge and swing my sword after the charge it only has mini-crits. Does it depend on the charge time, or the timing of my sword swing? Here is my loadout if it helps with finding an answer.

 

Alibaba's Wee Booties

Tide Turner

Persian Persuader

 

Thanks for helping out! 

[Scott Bakula]

https://wiki.teamfortress.com/wiki/Charging

[Alecto]

Tide turner only provides mini crits.