Upvote:1
Keep in mind that the Bastille was a fortress, and a large armory. The main weapons at the time were muskets, which the Bastille had plenty of in addition to tons of ammunition.
Upvote:2
The Wikipedia entry on the Bastille says in its paragraph about the storming of the Bastille:
[...] an additional force of 32 soldiers from the Swiss Salis-Samade regiment had been assigned to the Bastille on 7 July, adding to the existing 82 invalides pensioners who formed the regular garrison [...] The Bastille was defended by 30 small artillery pieces [...] He [sc. Bernard-RenΓ© de Launay, commander of the Bastille] was protecting a recently arrived stock of 250 barrels of valuable gunpowder [...]
French artillery was apparently standardized under the De Vallière system since the 1730s, so one can reasonably assume that "small artillery piece" would refer to a 4 pound or 8 pound (weight of the cannonball) gun.
Following Wikipedia further this is confirmed in the main article on the storming of the bastille:
The walls mounted eighteen eight-pound guns and twelve smaller pieces.
The fact that this is on Wikipedia might indicate that this is trivia by the standards of history SE.