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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.

Gyrojet Mark 1 Model B

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.


The Young Man will be dropping by to drool later on.  For now, that is outstanding.  He has immersed himself in the ABCs of Reloading, explained the difference between powders, the need for head space and why he will never buy another rimfire weapon.

He did take a peek at your new whatziss and made a comment to me, which I will let him make.
Making this gadget even more hazardous is a phenomenon collectors of old model trains know as "zamac rot" in which the metallic stew corrodes and breaks down.

I wouldn't want to fire one of these without a full EOD suit!

The Young Man will also need to explain his hostility to rimfire...
Congrats on the great find.

These are really neat weapons. Clever, innovative, albeit impractical and over hyped.

Watch for Mel Carpenter's book on Gyrojets and MBA when it comes out.  There is much more tothis story than is apparent from just one of the pistols.

Wish I had grabbed the Gyrojet carbine and presentation pistol when I saw them....
As I vaguely recall the Gyrojets almost got reclassed as destructive devices, but a collector had the foresight to get an opinion in writing from the (then) BATF that they were not Class 3.  He was able to produce the documentation several years later saving himself and other collectors a lot of headaches.  Nice find!
The 13mm Gyrojets are on the C&R list. Still subject to the normal rules under GCA '68, but not, as you note, DD's under the change to the NFA.  And it took some doing to get that done. 
You Sir, are blessed.   Congrats on that acquisition. 
I managed to locate this if you are intereste (as I was)
Don't you feel just a little guilty taking advantage of that little old widow or his witless children? LOL
Frank - no.  People managing the estate sale are the ones who failed, in that sense.  And there wasn't a widow or children, the family concerned was nieces and nephews and such. 

I have a book for SWWBO or Andy that tracks the collection - so something like this won't happen to them.

Had there been a widow, I would have brought it up, actually, and offered to help them get full value for it.

Buncha vultures?  Naaaaah.
Not all neices and nephews are vultures, John.   When THE Col (my uncle) died last year at the grand age of 103 (!!!!!), that was all the family left to him.    I think the cadets and midshipmen he trained were his children in his eyes.  He had taught engineering at both Anapolis and the AF Academy.    I do know he favored the neices and nephews who had 'sworn the oath' - regardless of the branch of service.  

He left his military memoribilia to the Marine!Goth - and his weapons collection had long since been sold away (sob). 

Of this particular bunch of vultures, I know whereof I speak.  I wasn't meaning to generalize out beyond that one sept and clan.
I wish I could say the same.

When my Grandfather passed he wasn't in the ground a full 3 hours when relatives were already squabbling over who got what, including the property that my grandmother still lives on to this day!

Case in point. I have an aunt who is to recieve their home when my grandmother moves on as it were. She went ahead and moved secure her claim.

Foolishness in light of the more important thing  that was gone, in my eyes anyway
As I wrote in the other thread, that is a kewel nerd piece with no practical utility.

Except: If somebody would mass-produce the ammo,  ennybody with a vise, files, drills, etc. could make launchers for them. Don't need no strong steel barrels to withstand the pressure, or nuthin. As was written, the piece is mostly cheap zinc alloy. Don't need no rifling machines, either.

But, yes, pistols are for short ranges, and the things don't get any velocity on them until longer ranges, where they are innacurate. 
Dammit, "inaccurate"!
All I can say, is you lucky, lucky bastard. And if I didn't already have one of my heart's desires (Double rifle) I'd be insanely jealous and full of a murderous rage. Now I'm just insanely jealous.
Heh.  Og, why, when I read this, does the emphasis seem to come at "bastard" and not "lucky?"
Back in my yuth I owned a gunstore and took a Gyrojet in trade, with a handful of ammo, and being a curious person, promptly went to our local range to try the gadjet out.  I was discharging the Gyro  about 20 feet from a B2 target that had a 20 foot berm backing up the target - the first round never hit parer and I could see no evidence of it hitting the berm, it's probably in ordit!  The second round had a slow ignition and sat in the tube flaring up before launching itself into the Van Allen belt!  I didn't know whether to drop the thing or hang on, but I hung on and it went.  Later when I was with MAC we tried a flare version at 2 AM, after much scotch, and it promply brought a helocopter from Dobbins Airfield to investigate us...Those were the the goode ole days...
I'll let you draw your own conclusions. Damn.
A friend had a Gyrojet in the early 70s. I saw it fired twiceand he shot it underwater once and said it looked like a torpedo. He was lucky it didn't break the surface. A local hardware store had a box of ammo and didn't know what they had. I went to get cash and someone bought it before I got back. I think I still have a round someplace.
Oh, yeah, I was told the previous owner shot a cow that had to be put down with the Gyrojet at close range and it sorta cauterized the wound because it didn't bleed much so they had to shoot it again with something else.
Popular Mechanics did a blurb about the Gyrojet back in the '60s -- I remember one of the planned uses was to outfit SEALs with 'em to engage VC frogmen in underwater duels at long range.

My guess is the plan died a-borning when someone pointed out that visibility in Vietnamese rivers is measured in millimeters...
The Young Man will so present himself and 'splain.  I forgot to tell him about my comment.
We have a Pinewood Derby race to attend.