Geco 9mm Experimental


A friend in Germany recently sent me the following photo. I have the same cartridge in my collection. I obtained it in 1995. At the time I was told that it was a Geco experimental. Note the half jacket inside the casemouth. This jacket takes a magnetic so it probably GMCS. the overall weight of the cartridge is 181gr so it is probably a 115gr bullet. The headstamp is Geco 9mm Luger. The diameter of the lead projectile above the casemouth is about 7.5mm.

Can anyone tell us anything more about this cartridge? What was the purpose? When was it made?




Now we see better ;)


I would say, for want of a better theory , it is just what it appears to be a lead half jacket. The big problem with half jackets and the reason they never caught on was because the exposed lead portion of the bullet caused severe leading in the barrel and destroyed the accuracy. This looks like a very practical solution to the problem. Make the lead portion smaller in diameter so it doesn’t come into contact with the rifling and can’t cause leading.

Now the only other problem that they have to overcome with half jackets is that they are no cheaper to produce than a full jacket bullet and since their only real niche in the market is enconomy it makes them a bit pointless.


It’s a weird looking crimp and a thick case mouth. Visually it reminds me of the Simunition rds (minus the plastic bit), and the CQT load they make so that the “real” CQT ammo can be fired through the special safety barrel adapter used with simunition:

If you took away the plastic sleeve and made the casing all brass on the CQT rd, it might end up looking like Lew’s mystery cartridge with its oddly smaller diameter projectile.

Here’s a side-by-side comparison:

I would put the calipers to a CQT rd and see if its projo is also 7.5mm


DK, I think what you regard as the crimp is part of the projectile jacket and the case itself is of regular shape.


I wonder if that portion around the base of the projectile is a “half-jacket” in the traditional sense, or if it is an integral part of the inside of the casing and stays bonded to the case upon firing or some weird thing? Basically I wonder if the barrel that this was mean to be fired into was actually 9mm, or if it was 7.5mm for some sort of odd sub-caliber device like a simunition thing.


DK, look at the center image of those 5, it should explain everything.



The case is brass. The area I’ve called the half jacket is GM plated steel. I can even feel the end of the bullet when I run a magnet down the outside of the case. What you are calling the crimp is a different material from the case so it is unlikely to be an integral part of the case.

Hammer, thanks for the better photos. I assume the cartridge is your.

I agree with Vince that a commercial half jacket round makes no sense. My guess this is a police project of some sort. I got it from the same source many years ago that also provided two FMJ rounds with a very similar ogive, but both had steel cores. The bullets were full weight (8g I believe) and also a pointed FMJ round.




I just got an email from a friend in Germany (Rolf Foerster) who was the source of my cartridge. The cartridge is the FZ 61 NG apparently. It was a “Development short range weight reduced bullet.”

The box label below reads: 8g lead bullet with rear / tail cup

There is also a nice photo of the bullet.

Apparently this is a pretty unusual cartridge with just a few specimens out in collections.