20mm question

I recently started collecting WW2 militaria, and I got a 20mm shell for Christmas. Total length is 185mm, excluding the projectile its 110mm. It says “NECO 1942 20MM M21” on the headstamp, and some other text I can’t read or get a good photo of around the tip of the projectile. My own research on the headstamp tells me its for a Hispano autocannon and was made in Wisconsin.

My main question is, what kind of shell was this originally? Was it HE, AP, or something else entirely? I’d appreciate anything else you could tell me about it though.

Howdy & welcome RyanL
Your question could be perhaps answered with daytime photos or noting the bullet colors and any markings

As Pete alluded to, the projectile color tells the tale, but the basic projectile was used for almost all the various loadings, they just changed the contents of the projectile. Those contents then determined the color the projectile was painted. The nose fuse was either inert or live depending on loading, ditto on tracer being added or the projectile being plugged.

Thanks for the help.

I have two more photos, hopefully these have more satisfactory lighting. If not, the part of the projectile that is not brass is a chocolate brown.

Also, I found a strong enough magnifying glass to read the markings towards the tip of the projectile. The spacing of the second line might not be totally perfect, as I’ll have to guesstimate how many times to hit the spacebar. Also, I used asterisks in place of a mid-line dot, as I can’t type that. Anyways, text is as follows:

N 253 1 U

There’s some damage around the “N”, so there may have originally been other markings between the “N” and the “253”.

Last, the painted part of the projectile is magnetic, but the tip is not.



It looks to have been re-painted as the copper rotating band is the same color as the body. Also that the fuse doesn’t fit as it should, (a gap between it and the body), and the bullet also has a gap between it and the case mouth.
So I’m sorry I can’t be of much help in identifying the original load.
The bullet and fuse and case may not all be original to each other, or it may well be original, as it is it’s hard to say.

The bullet does come off the case. I can see a little damage in the paint around where the fuze attaches to the body, and it appears to be black underneath the paint.

Is it possible that the gaps are simply the result of deactivating the round? Like they had to remove the fuze to deactivate the round, and simply could not re-attach the fuze as well as it was at the factory?

20mm isn’t my particular forte, but it looks like a 20mm Oerlikon projectile fitted to a 20mm Hispano-Suiza case. In the oerlikon series, dummy would be a brown projectile, but it’s a real brown, this one looks definitely repainted to another variation of brown, more like copper and is it metal flake?

Morning Ryan
the fuze is threaded & the threads match, so if removed it should go back again, just like a nut on a car. If the threads are buggered up that will stop it, or if the threads don’t match. ie: made on different machines in perhaps different factories - not original to each other. Paint looks to be in the gap, so that is a possible problem.

If black underneath that is likely the true color, and is the fuze a fuze or a dummy fuze.

I also agree with Keith that looks to be an Oerlikon proj. & not a H.S. proj., which you have correctly identified the case as being, so you have a bad marriage.

Posting this here since its so similar and I don’t think I should start a new thread for this.

A friend over at the Historical War Militaria forum needs help identifying a 20mm shell he’s got. We’ve managed to conclude its been fired because you can see what appears to be marks caused by the rifling in the driving band, and we believe its a dummy round because it’s blue.

TP-T: Target Practice - Tracer (no war head)

The M71A1 tells you which caliber and bullet type

TTT is tracer code. Blue is Target Practice

Definitely a fired projectile.

Any way to tell if this is a hispano-suiza, oerlikon, or something else entirely?

Ryan, your projectile here is a 20x110 Hispano “TP-T” target practice tracer and was made in Belgium. The “HIS SUB” indicates the use in an artillery subcaliber system like it is not uncommon with tank guns and some other artillery.
This is no dummy projectile as any kind of dummy is not meant to be fired. Also all declared dummies are totally inert. Your projectile here was loaded onto a case with a real propellant charge and should not be confused.
Also never assume any blue painted ammunition to be “dummy” in the meaning of harmless or the like. The blue paint just means “practice” (and not for combat - usually) without any statement on the content of an item and in particular it is no identifier for inert ammunition. There is plenty of blue painted practice ammunition which is containing the full spectrum of explosives ranging from pyrotechnics, propellants and black powder up to high explosives and all sort of flammable or otherwise dangerous liquids.
So please keep in mind that “blue” can be as dangerous as any other ammunition. When in doubt always seek professional advise.

Thank you for the assistance.