20x110mm Oerlikon "FSC 1945 20mm MK4"

This one is made by Florence Stove Company. Is this projectile correct to the round? What is projectile’s functionality? Is this a HE-T? Why is it not painted? The projectile has 2 cavities.


Based on the information provided in your question here and on BOCN:

Projectile not painted? a) paint has been removed, b) projectile was never painted.
As the above information indicates the projectile is correct for the Oerlikon cartridge case. The MK. 4 designation in the headstamp indicates the use of a reinforced primer.
Note the two “cavities” in the sectional diagram above; high explosive projectile with tracer OR the projectile could be BLIND LOADED (no explosive element) (BL & T designation) with tracer for training use.


Thank you, Brian. I’ll take it that the entire body of my projectile must be the same colour as the nose, to be original.
I have a related question. The descriptions above mention “integral” tracer (which I take to mean as being inside the projectile’s body). What would be an example of non-integral tracer?


Hope this helps.

Integral- adjective: integral necessary to make a whole complete; essential or fundamental, included as part of the whole rather than supplied separately; having or containing all parts that are necessary to be complete. Oxford Dictionaries

Tracers- … Tracers are either screwed or pressed into the aft end of the projectile and may be set into the interior of the projectile, in which case they are internal tracers, or they may project from the end of the projectile in which case they are called external tracers…
Page 377, U.S. Navy Projectiles and Fuzes, 1945, U.S.N.B.D.



A tracer can also be contained in a plug that is screwed into the base of the projectile, usually with a left-hand thread. I don’t think that 20mm are made that way but base tracers are very common in larger projectiles (40mm +).


an exemple for 20mm:

20x82 and 20x138 flak rounds can be seen with base screwed tracers

The 20x82 actually not much unless you are talking about AP loads.

maybe reconstitutions with a 20mm flak shell and a 20x82 casing

Yes, “stuffing” may be here the case. This happens unfotunately too often.