H&K G11E

The H&K G11E is an advanced version of the regular G11, a weapon that revolutionized squad level support weapon design. The gun fires a caseless cartridge consisting of a block of propellant with a bullet buried inside. The resultant weight and space savings allow it to have a very high magazine capacity.

Locations
Snake Morton, one of the Morton Brothers, uses this gun. Failing that, it can be purchased in San Francisco. Also, some Hubologists that one can encounter outside of San Francisco also carry this weapon. Killing these Hubologists does not decrease (or increase) one's Karma, and will not make the Hubologists in San Francisco turn hostile, even if you kill thousands. The Enclave soldiers that wear combat armor in Navarro also have these equipped. Also random enclave patrol encounters carry them.