Gyrojet Mark 1 Model B

So, every now and again, as a collector, you have a Great Day.

How do I define a great day? When I find a weapon generally valued in excess of $1000 at an estate sale for $25. Because the people who organized the sale didn't know what they had. They thought it was a toy pistol, because the recently deceased owner had a collection (a nice one, too) of toy pistols.



It was a Gyrojet Mark 1 Model B. With six rounds of ammo, which they thought were toy bullets that used caps.

Sweet. Heck, who knows, the original owner may have thought it was a toy. It is certainly toylike. But they aren't. They are dangerous indeed.

Because it doesn't have to withstand the pressures of a conventional firearm,it doesn't need to be of the same robust (and expensive) construction. The bulk of the pistol, the two outer halves, are made of "zamak" (aka "Mazak" in Europe) which is that same greyish alloy you remember your toy cars and guns being made of. You probably know it more commonly as "pot metal." It is comprised of aluminium, magnesium, and zinc. The thing weighs less than a pound. And is painted black. This is the most basic version of the pistol - the one in the collection of the Arsenal.

There is a very thin-walled steel tube for a barrel, which mainly serves to keep the rocket-propelled bullet oriented along the line-of-sight as it gets to speed.I'm not sure what the internals are made of, other than they have to be a bit more robust as they serve as bearing surfaces and the hammer does have to take repeated impacts. I can tell you when you take it apart to see how it works... it's a little counter-intuitive as to the process to re-assemble the thing. It took me about two hours to figure out how to get the fiddly bits to align, under spring tension, and stay in place long enough to get the halves back together.

Speaking of impacts - as some of you noted in the "Whatzis" post, the hammer goes backwards, striking the head of the bullet, which then pushes the round back onto a fixed firing pin, which initiates a cap which then ignites the rocket. The rocket sits there for a bit as it develops sufficient thrust to overcome the hammer spring tension, then moves forward, pushing down the hammer and re-cocking the pistol, and then enters the barrel and heads on downrange.  You notice in the picture that the barrel starts *after* the space for the hammer - and the ports in the side of the weapon are open - that is so that the exhaust gases have a place to go.

That using the hammer to hold the round while it develops thrust and then using the rocket to re-cock the piece I believe is intentional design; making a virtue of a vice. The vice being the relatively slow development of thrust and the impact that could have once the rocket leaves the barrel - having to overcome the hammer means the round will have started to develop some serious thrust, meaning it will gain kinetic energy more quickly as it moves down the barrel - though not enough to make the pistol a reliable close-in defense weapon, as its penetrative capacity close-in (where most self-defense actions take place) is pretty low - compared to its energy at motor burnout, where, according the MBA Inc, the maker, the round has greater impact energy than a .45 ACP.  See the link at the end of this regarding the testing of some gyrojet ammo.

These guns were tested by the military and found lacking for many reasons, not the least of which was accuracy issues and ammunition reliability. It's also a real pain to load - there being nothing like conventional magazine lips to hold the rounds in (because they aren't going to be stripped out of the magazine by a recoiling slide) the shooter has to hold the pistol and depress the magazine spring, load in the rounds, which just drop in place (and don't always do so correctly) and then, while holding the follower down under full tension, get the receiver cover closed, and let up the pressure on the magazine follower to lift the rounds. If you have a dud, you have to be careful when opening the receiver cover... as the rounds are under full spring tension, and the cover is what is holding them in place. Don't manage that correctly, and "spoiiiinnnnnnnng!" your rounds are flying through the air, but not in the manner you wished. Imagine dealing with that in combat...  if you do want an idea of what it was like - meet Captain Mendenhall.

For more on the gyrojet's problems, from guys who are trying to solve them - The Deathwind Project.

Captain Mendenhall in Small Arms Review on his testing of the Gyrojets.