Need info on 20mm shell

I just came upon a live unfired 1942 20mm MK 2 shell. I have been looking for info on this but can not find much. If anyone knows anythig on these shells please let me know. It is an original with all cereal numbers on the brass and the projectial.Thanks

Measurements would be handy (case length), and type of rim (see below): Your cartridge is most likely rimless or rebated. If it is rimless it is likely a 20x110 Hispano, if it ir rebated it is likely a 20x110RB Oerlikon Type S.

Once the rim type is confirmed, we can tell you more. Are there any other markings besides “1942 20mm Mk 2”. A photo would also be helpful if possible.

What is it that you want to know. This is a very common 20 mm round. To be able to help you we need to know the headstamp and colors and markings on the projectile. A nice scan or photo of the cartridge would be nice.

  • @ tnix: You mentioned a “1942 20mm Mk2” shell. Only a US made 20mm Oerlikon “S” [20X110RB] has these markings. Since there is the mark “Mk2” [and not “Mk3”] the shell case is made of brass [not steel]. The year of shell case manufacture is “1942”. On the headstamp must be the shell case maker’s mark too [like “AG” or “ASC” or “B” in a diamond frame, etc]. Black ink markings on the side of the shell case give more info about load, date of loading, facility code, info about propellant, etc. —> NOTE: You also mentioned “live unfired 1942 20mm Mk2” which means a VERY DANGEROUS item. Liviu 10/14/07

I have one round with : A.S.C. 1943 20 MM-Mk-2 as a head stamp. The projectile has a flat nose with a grey cap. I believe that this was found in eastern Canada. What exactly is this loading ?


To All Interested:

Here’s a list of USN 20mm Oerlikon loadings and color codes, as extracted from OP 1664, Volume 1 “U.S. Explosive Ordnance”, 28 May 1947. I prepared this in table format, and hope it posts as I’ve typed it.


HE, Mk.3 Tetryl White
HE, Mk.3 Pentolite Yellow
HE-I, Mk.3 Tetryl & Incendiary Mix Red
HE-I, Mk.3 Pentolite & Incendiary Mix Light Pink
HE-T, Mks.4 & 7 Tetryl & Tracer Light Grey*
HE-T, Mks. 4 & 7 Pentolite & Tracer Blue*
AP, Mk.9 Tracer Black
BL & P, Mk.3 Inert Loaded Dark Green
BL & P, Mk.7 Inert Load & Tracer Dark Green w/Yellow Stripe
Drill Empty Seal Brown
HEI-T Not Shown Bright Green

*When those projectiles marked with an asterisk are assembled with Dark Ignition Tracers, a 1/8" wide Bright Red band will painted around them.

The fuzed rounds use a Mk.26 Series PD Fuze, which is an air column fuze.


  • @ Glenn: The headstamp mark “Mk2” shows a 20X110RB brass shell case with British type primer. The shell case maker’s mark “A.S.C.” stands for “A.S. Campbell Co. Inc.” from Boston [MA]. — NOTE: Each type of 20mm projectile for the 20mm Oerlikon “S” round [20X110RB] had a code: “ZA”—> HE; “ZB”—> HET; “ZC”—> HEI; “ZD”—> AP; “ZE”—> APT; “ZF”—> BL & T; “ZG”—> BL & P; “ZH”—> HET-DI I hope this is going to be of some help. Liviu 10/14/07

Liviu -thank you .
I obtained this round when I was asked to indentify this cartridge for a client. He never paid the bill-I kept the cartridge. When I started reading this I thought that it was a good time to finally understand just what I have. I believe that this was found in Thousand Islands Ontario on a WW2 aircraft wreak site.


Thanks everyone for the info.I will post a pic of the round as soon as I can.Also how do you think I should store this round since it is a live round, and how rare is it that it is unfired.

Photos of Glenn’s 20mm. What is it?


  • @ Glenn: I have a fired brass shell case of 20mm Oerlikon “S” [20X110RB] having the same headstamps markings, the difference is that my spent brass case is dated “1942”. —> The company “A.S.C.” [“A.S. Campbell Co. Inc.” from Boston / MA] manufactured 20X110RB brass shell cases in 1942-43 [“Mk2”] and in 1944 [“Mk4”]. I would like to mention that the same company also manufactured 20mm Hispano [20X110] rimless shell cases made of brass in 1942 and made of steel in 1942-43. Some 20mm Hispano [20X110] brass shell cases made in 1942 may have on the headstamp the maker’s mark “ASCO” which was actually “A.S.C.” Liviu 10/15/07

Hi, All…I have a U.S.Navy BuOrd (Bureau of Ordnance) Cartridge Board from 1944 with all the 20mm on it, both Navy and Army, as they are called on the board…whole and sectioned rounds…can post pics if anyone is interested…Randy


Very interested in seeing the board. Please post pics.