No, you didn't hear wrong. Yes, the movie. This is a sound identical to the chaingun Neo uses in the helicopter right after the lobby shooting spree to get rid of the Agents in the same room with Morpheus. The only difference is has a slightly reduced rate of fire to match the chaingun a bit more.
To tell you the truth this isn't my sound, and I couldn't remember for the life of me who's this is, or what the site was that I got this from.
*sigh* Oh well, just install it!
If you're the creator of this sound and happen to stumble past here and notice this, drop me a line at [email protected]. I'd be glad to give you credit, or remove it if you really want.