What do Belken Devices say for "load cartridge"?
Here's a quote from the manga wikia on Vita's list of attacks:

Nachladen — Not a real attack, just Graf Eisen reloading cartridges.
Explosion — Also not an attack; Graf Eisen says this when using cartridges, analogous to the English-speaking devices' &quot;Load cartridge.&quot;

Source: Vita (Nanoha) Manga Wikia page
Nachladen is also the term listed on the Signum manga wikia page, a German word which translates to &quot;Reload&quot;.
Despite what the manga wikia says, I always thought that the Belken devices use &quot;Reload&quot; in the same way that the Mid-Children Devices use &quot;Load Cartridge&quot;, and &quot;Explosion&quot; is when they're being used, particularly multiple cartridges. (Passing reference of this on the Nanoha wikia Vita page).
I admit that I have not watch/read/listened to all of the anime, manga, drama CD, etc. and my understanding is that there may be minor differences.