McGyro,
Here is a link and a small selection from the web page.
[url]http://www.classicfirearms.org/feb2000mbaGyr.html[/url]
Thanks to David Kirschbaum, who actually used a Gyrojet in a combat situation, for this information:
Okay, here it is, from the horse's mouth. I carried one in combat, so this is personal first-hand experience, and from an SF [Special Forces] Weapons Man at that.
I was issued one, a 13mm Bensen Gyrojet, in Vietnam, SOA (CCC), in February or March 1969, right out of the supply room, along with a couple dozen rockets. I used it as my "belly gun", on a lanyard around my neck and tucked into a claymore bag across my chest. It was very light, even fully loaded, so the weight wasn't a problem. A little big and bulky, but no worse than a .45, and shorter than the .22 silenced Hi-standards that were also available.
Military testers were first intrigued and then disappointed by the Gyrojet. Under certain humidity conditions, the Gyrojet round often left a temporary but noticeable vapor trail leading back to the shooter! The feature could prove fatal to the firer in a combat situation.
NOTE: The Gyrojet 'round', 13mm in diameter and 38mm long, was composed of two parts—a solid 'warhead' and a tubular body containing a propellant charge.