20 X 110 USN HPT Dummy


I have a 20 X 110 U.S. Navy dummy with a lavender projectile shaped as can be seen below. It is headstamped GLM 07-82 20MM MK5 MOD-0. It has a cromated steel case. When I obtained this round back in the 1980’s I wrote on the side of the case exactly what this dummy was. It has since been mostly been rubbed off. All I can now read is “High ??? Test Dummy” Can any one tell me the full nomenclature for this dummy. Also, why is the projectile not seated completely in to the case. The overall length (183mm) is correct as seated compared to a standard brown projectile dummy round. Can anyone identify the maker GLM?


Hi Ron!
I have seen this round before and it was called a “PROOF ROUND”, when I saw it for sale. I am sure their will be others here in the forum that will offer you a more detailed description then “Proof Round”. :-) I have seen it offered for sale a few times but none of them were in near as nice shape as yours. It looks minty!



Also, not sure if thier is any truth to this, but I was told that purple is the color for “experimental”? This was told to me by a ordnance collector in the UK.


The projectile appears to be from a 20x102 M54 High Pressure Test round. I’ve never seen it loaded into a 20x110 Navy case, but there’s a lot I haven’t seen so that doesn’t mean much :). I have one loaded in a 20x102 case with no markings - it’s crimped in and the primer is unstruck, but there is no powder in the case. I’m not sure if it’s a display dummy or something else.

GLM is Globe Metallurgical Inc. in Beverly OH.


APFDS–Yes, purple in the UK does mean experimental, but that is a deep purple, almost black.

JASON: Proof and High Pressure Test are the same, only this is a factory made dummy. Were the ones you saw for sale dummy or live. And, yes, this is factory new mint condition.

The word “pressure” would be the right length to fit where my label is smudged. So, I think this is a 20 X 110 USN High Pressure Test Dummy.

TWO_AZ: I agree that it appears to be a 20x102 M54 High Pressure Test projectile. To make it the proper overall length for the 20 x 110 USN it would need to be loaded as it it is because the original USN projectiles were longer than the M54.

In light of the determination that this is a Dummy HPT round, I will revise my original case material from cromated to stannic stained case. I thought it was awful bright for cromated.

Now, for what reason were these made. This is definently a factory job, not home brew. If made for display or training, why the incorrect projectile?


Thanks Ron. Did not know that it was the same :-) Sorry for that. The ones I saw for sale were not live rounds.