Keychain mini-gun that shoots

That? No the Warthog mounts a GAU-8/A Avenger, a 30mm cannon.
The XM196 is an M134 variant for the Cheyenne and is 7.62mm.

Also worth noting is that any equipment with an XM number is experimental equipment and may never have been fielded. Like the XM8 and the XM214.

Makes sense XD,I would still like to see a wee lil' minigun though

Wee lil'? Look up the XM214. That thing was tiny!