Bored? You can fire your Gyrojet underwater


Robert Mainhardt in the swimming pool of his home near San Francisco:

At the office:


Maybe I’m imagining this, but didn’t one of the early James Bond films (maybe Thunderball) have a scene where the bad guys (or maybe it was the good guys) were using Gyrojet rifles in an underwater skirmish? I don’t think they were identified as such, but that’s what they looked like.


Fede; Your pictures of Robert Mainhardt appeared in the May 27, 1966 issue of LIFE magazine. The underwater pic was indeed made in Mainhardt’s swimming pool, and was taken by Jon Brenneis. The vertical white stripe is where two pages of the magazine (pages 46 and 47) came together in the center.

The second picture was taken in Mainhardt’s offce at MBA headquarters on Bollinger Canyon Road in San Ramon, California. The underwater speargun is shown in the lower left of that photo.

That issue of LIFE was extremely important to MBA. It gave the company (and Mainhardt) a lot of much-needed publicity worldwide. Standard Gyrojet firearms would in fact fire underwater since their double-base propellant had its own oxidizer, but their range was very short. MBA developed a series of underwater launchers, most of which used long, slender Lancejets which were gunpowder powered. Some of these were proposed to the U.S. military, but none were adopted.

To see Gyrojets in action, watch the James Bond 007 movie “You Only Live Twice.” Mainhardt provided all the Gyrojet firearms and rocket ammunition, plus the Finjets, and was a technical advisor on the movie.



Mel, thanks for your comments. These pictures come from that same magazine.


Everything about Gyrojets and their related products is covered in detail in Mel Carpenter’s SUPERB book!

Every cartridge collector should have a copy, not just for the technical details (which are amazingly creative) but for the insights into why MBA developed products and made decisions regarding various details. It is a sharp reminder that ammunition (and other) companies exist to make a profit, not just make a product, and that the market drives the products.

Buy the book! You won’t regret it.


Yes ! a purely fantastic book…a friend just got it for me from SLICS and I must confess that I am still stuck in it!

Many, many thanks to Mel…