20mm cases

grymster2007 · August 27, 2008, 01:21 PM

Mrs. Grymster sent me to pick up a piece of furniture she bought at an estate sale last weekend. When I got there I found a pile of used brass, mostly .38 SPCL, which I can load for my kids. I decided to buy it and the lady there also threw in some spent 20mm cases.

They are about 107mm (4.25") long and are headstamped "E.K. 1943 20 M.M. Mk.2".

I think I'd like to make a dummy projectile for one or two of them, clean them up a bit and keep them as novelties.

Can anyone tell me anything about these, such as the type of gun they may have been used in and/or what the projectile may have looked like?

MacGille · August 27, 2008, 03:04 PM

20 MM Oerlikon AA gun. Sometimes mounted on halftracks in WWII. Always mounted on ships as secondary AA guns. Could be from the Boyes 20MM anti tank rifle but they were scarce.

**44 AMP** · August 27, 2008, 11:32 PM

While the majority of our single seat fighter planes in WWII carried .50 cal browning machine guns, some of our aircraft did mount a 20mm cannon as well. The P-38 Lightning did, as did some versions of the P-39/P-400. The P-61 night fighter carried several (4 IIRC), and so did some light bombers. Our Allies had a number of planes with 20mm cannon in them, as did our enemies in WW II. Also there were "anti tank rifles" in 20mm, developed before WWII, and used early in the war, until the tanks became too thickly armored for them to be effective (which didn't take long), the most famous are the Solothurn and the Lahti, both of which were sold mail order surplus here in the states during the 1950s and early 60s.

There are some dimensional variations between the cases of the different 20mm rounds, so all 20mm ammo is not the same, just as all .30 caliber rounds are not the same. Some cases are longer/fatter than others, just like rifle rounds.

SDC · August 28, 2008, 07:23 AM

We'd need some more information, mainly the case measurements or a picture to know for sure, but they SOUND like Oerlikon cases for one of the variants of the Oerlikon FFV that was adopted by the US Navy; these can commonly be seen in footage of the Kamikaze attacks, trying to knock the planes down before they can get close in enough to damage the ships. Similar rounds were used in aircraft cannon by the US, England, Germany, and Japan, but this is where we'd need the pictures and/or dimensions to know if you've got some of those. Anyway, the below picture is what PROBABLY fired the cases you've got.

You can find a table of measurements and case types at: http://www.quarry.nildram.co.uk/ammotable2.htm , and pictures to go with those measurments at http://www.quarry.nildram.co.uk/20mm1.jpg ; in US use, the two right-most rounds were the most common, and the second from right is what would have been fired in the above gun, the case may look slightly different because the Oerlikon blows the shoulder forward when it fires, as it works like a big submachine gun, with a bolt that isn't locked forward when it fires.

grymster2007 · August 28, 2008, 11:23 AM

Quote:

we'd need the pictures and/or dimensions to know

Hey thanks, people!

I'd really like to machine a projectile for one or two of these and would like for them to look authentic. It looks very similar to this image I googled. Would that be a separate brass ring at the base of the projectile? Or is that part of the case?

grymster2007 · August 28, 2008, 11:46 AM

SDC,

Thanks for the info. I think it looks most like the 20X110RB. On the table it lists nationality as "CH"; would that be China?

**Mike Irwin** · August 28, 2008, 12:06 PM

The brass ring at the base of the projectile is the driving band. The projectiles in these rounds were typically steel, more like an artillery shell, because they contained explosive compound. You needed a driving band of a softer material to take the rifling.

The headstamping on your round indicates that it is most likely American made. Given that the most commong 20mm, by FAR, was the Oerlikon anti-aircraft gun, that's very likely what this one is.

During WW II the Chinese, to the best of my knowledge, used no 20mm guns.

After WW II they rather quickly came under Soviet influence, and the Soviets used 23mm guns, not 20.

"Could be from the Boyes 20MM anti tank rifle but they were scarce."

Actually, they were non-existent. The Boys rifle was a .55 caliber.

**Mike Irwin** · August 28, 2008, 12:16 PM

OH, the E.K. headstamp?

Eastman Kodak, Rochester, New York.

Most sources indicate that they only made ammo from 1944 to 1945, but I've seen several E.K. 1943 marked shells in the past, as well.

I suspect they didn't enter full-scale production until 1944.

The clincher?

Eastman Kodak made ONLY 20mm Olerikon ammunition. No small arms or machine gun ammunition, nothing heavier.

grymster2007 · August 28, 2008, 12:28 PM

Thanks Mike!

So would you agree that my case would likely be a 20X110RB?

**Mike Irwin** · August 28, 2008, 12:34 PM

Barring seeing an actual photograph of your cases, I would say yes, these are the 20x110 Oerlikon cases.

Here's a picture from Tony Williams' site. He's a well-known collector.

grymster2007 · August 28, 2008, 12:38 PM

The cool thing about all this is that for my $18, not only did I get the 20mm cases, a whole bunch of .38SPCL, some .45 ACP and .44 magnum cases, but I also picked up three three calculators at the estate sale. Two of which are very nearly NIB HP 15C scientific calculators.

Mrs. Grymster was giving me a hard time about the calculators, until we got home that is, and I demonstrated that they're worth between $300 and $400 each.

I'm actually feeling guilty.... like I robbed somebody.

SDC · August 28, 2008, 12:42 PM

Quote:

Thanks for the info. I think it looks most like the 20X110RB. On the table it lists nationality as "CH"; would that be China?

It's actually a Swiss design, that Oerlikon ended up licencing to several other countries; if your cases look like the ones in your photo, with a rebated rim, they're definitely Oerlikon cases, and the shoulders should have been blown forward on firing. Mike's headstamp info confirms them as the 20x110; here's a short clip of a single-mounted version of one of these guns being fired:
http://www.youtube.com/watch?v=hW8DSJYS204

grymster2007 · August 29, 2008, 08:57 AM

Thanks to all your help, there's not much doubt that they are 20X110RB. But here's a couple pics and some dimensions.... since I went through the trouble!

**Mike Irwin** · August 30, 2008, 09:19 PM

I missed this...

CH is not China in international lingo, normally.

CH is Confederation Helvetica.

grymster2007 · August 31, 2008, 08:09 AM

Quote:

CH is Confederation Helvetica.

Good call Mike!

Now that you mention it, I think China is abbreviated "CN".

Mach II Sailor · August 31, 2008, 08:51 AM

grymster, your 20mm cases, in my OPINION are definitely NOT made for any American 20mm gun, the 20mm rounds in my collection (i have 8 of the "old" 20mm, and none look like yours) have necks for the projectile and the rims are NOT rebated.

Tombstonejim · August 31, 2008, 09:47 AM

Look here the british version had a shorter case for some reason.

Gun Characteristics
Designation USA: 20mm/70 (0.79") Marks 2, 3 & 4
British: 20mm/65 (0.79") Mark II

Ship Class Used On Almost all
Date Of Design about 1939
Date In Service 1942
Gun Weight 150 lbs. (68.04 kg) (including breech mechanism)
46 lbs. (20.865 kg) (without breech)
Gun Length oa 87 in (2.210 m)
Bore Length 55.1 in (1.400 m)
Number Of Grooves 9
Length Of Rifling N/A
Chamber Volume N/A
Rate Of Fire 450 rounds/minute per barrel

jrfoxx · August 31, 2008, 11:19 AM

Neat find, Grymster2007.

Also, I'd LOVE to get a hold of one of those 57x441R shells in Mike Irwin's pic there. That thing has to be huge, and quite impressive/imposing looking.

**Mike Irwin** · August 31, 2008, 02:00 PM

Mach II,

What years are stamped on your case heads?

The Navy, in the 1950s, adopted a different 20mm that had a different case style, and also used a somewhat shorter case; 20x102mm Vulcan.

If I'm not mistaken, that 20mm is now the same type that is used in Navy and Air Force gatling guns on air craft and also the guns that armed Cobra helicopters.

The markings and dimensions are correct for a WW II 20mm shell in US service.

If you look at this picture, the third one is the modern Vulcan; the fourth one is the 20x110mm Oerlikon as used by the Navy during WW II. You'll have to click the link.

http://tinyurl.com/6xm4ff

It decided has a rebated rim, a longer, shallower shoulder, and virtually no neck. Given the markings on Grymster's case, it's definitely a WW II Navy Oerlikon gun round.

**Mike Irwin** · August 31, 2008, 02:03 PM

Tombstone,

The British round didn't use a shorter case.

The 20mm/70 and 20mm/65 means that the barrel in the American gun was 70 calibers (70x20mm) long. The British gun had a barrel that was 5 calibers shorter.

That puts the American gun with a barrel of just shy of 5 feet.

August 27, 2008, 01:21 PM	#1
grymster2007 Senior Member Join Date: May 22, 2007 Location: In the oak studded hills near Napa Posts: 2,203	20mm cases Mrs. Grymster sent me to pick up a piece of furniture she bought at an estate sale last weekend. When I got there I found a pile of used brass, mostly .38 SPCL, which I can load for my kids. I decided to buy it and the lady there also threw in some spent 20mm cases. They are about 107mm (4.25") long and are headstamped "E.K. 1943 20 M.M. Mk.2". I think I'd like to make a dummy projectile for one or two of them, clean them up a bit and keep them as novelties. Can anyone tell me anything about these, such as the type of gun they may have been used in and/or what the projectile may have looked like? __________________ grym

August 27, 2008, 03:04 PM	#2
MacGille Senior Member Join Date: July 6, 2006 Location: Planet Earth Posts: 976	20 MM Oerlikon AA gun. Sometimes mounted on halftracks in WWII. Always mounted on ships as secondary AA guns. Could be from the Boyes 20MM anti tank rifle but they were scarce. __________________ If ye love wealth better than Liberty, the tranquillity of servitude than the animated contest of Freedom, go from us in Peace. We ask not your counsel or Arms. Crouch down and lick the hands which feed you. May your chains sit lightly upon you, and may posterity forget that you were our countrymen. --Samuel Adams--<*ixoye><

August 27, 2008, 11:32 PM	#3
44 AMP Staff Join Date: March 11, 2006 Location: Upper US Posts: 28,874	20mm cannon were also mounted in a number of aircraft While the majority of our single seat fighter planes in WWII carried .50 cal browning machine guns, some of our aircraft did mount a 20mm cannon as well. The P-38 Lightning did, as did some versions of the P-39/P-400. The P-61 night fighter carried several (4 IIRC), and so did some light bombers. Our Allies had a number of planes with 20mm cannon in them, as did our enemies in WW II. Also there were "anti tank rifles" in 20mm, developed before WWII, and used early in the war, until the tanks became too thickly armored for them to be effective (which didn't take long), the most famous are the Solothurn and the Lahti, both of which were sold mail order surplus here in the states during the 1950s and early 60s. There are some dimensional variations between the cases of the different 20mm rounds, so all 20mm ammo is not the same, just as all .30 caliber rounds are not the same. Some cases are longer/fatter than others, just like rifle rounds. __________________ All else being equal (and it almost never is) bigger bullets tend to work better.

August 28, 2008, 07:23 AM	#4
SDC Senior Member Join Date: January 23, 2001 Location: People's Republic of Kanada Posts: 1,652	We'd need some more information, mainly the case measurements or a picture to know for sure, but they SOUND like Oerlikon cases for one of the variants of the Oerlikon FFV that was adopted by the US Navy; these can commonly be seen in footage of the Kamikaze attacks, trying to knock the planes down before they can get close in enough to damage the ships. Similar rounds were used in aircraft cannon by the US, England, Germany, and Japan, but this is where we'd need the pictures and/or dimensions to know if you've got some of those. Anyway, the below picture is what PROBABLY fired the cases you've got. You can find a table of measurements and case types at: http://www.quarry.nildram.co.uk/ammotable2.htm , and pictures to go with those measurments at http://www.quarry.nildram.co.uk/20mm1.jpg ; in US use, the two right-most rounds were the most common, and the second from right is what would have been fired in the above gun, the case may look slightly different because the Oerlikon blows the shoulder forward when it fires, as it works like a big submachine gun, with a bolt that isn't locked forward when it fires. __________________ Gun control in Canada: making the streets safer for rapists, muggers, and other violent criminals since 1936.

August 28, 2008, 11:46 AM	#6
grymster2007 Senior Member Join Date: May 22, 2007 Location: In the oak studded hills near Napa Posts: 2,203	SDC, Thanks for the info. I think it looks most like the 20X110RB. On the table it lists nationality as "CH"; would that be China? __________________ grym

August 28, 2008, 12:06 PM	#7
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,390	The brass ring at the base of the projectile is the driving band. The projectiles in these rounds were typically steel, more like an artillery shell, because they contained explosive compound. You needed a driving band of a softer material to take the rifling. The headstamping on your round indicates that it is most likely American made. Given that the most commong 20mm, by FAR, was the Oerlikon anti-aircraft gun, that's very likely what this one is. During WW II the Chinese, to the best of my knowledge, used no 20mm guns. After WW II they rather quickly came under Soviet influence, and the Soviets used 23mm guns, not 20. "Could be from the Boyes 20MM anti tank rifle but they were scarce." Actually, they were non-existent. The Boys rifle was a .55 caliber. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.

August 28, 2008, 12:16 PM	#8
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,390	OH, the E.K. headstamp? Eastman Kodak, Rochester, New York. Most sources indicate that they only made ammo from 1944 to 1945, but I've seen several E.K. 1943 marked shells in the past, as well. I suspect they didn't enter full-scale production until 1944. The clincher? Eastman Kodak made ONLY 20mm Olerikon ammunition. No small arms or machine gun ammunition, nothing heavier. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.

August 28, 2008, 12:28 PM	#9
grymster2007 Senior Member Join Date: May 22, 2007 Location: In the oak studded hills near Napa Posts: 2,203	Thanks Mike! So would you agree that my case would likely be a 20X110RB? __________________ grym

August 28, 2008, 12:34 PM	#10
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,390	Barring seeing an actual photograph of your cases, I would say yes, these are the 20x110 Oerlikon cases. Here's a picture from Tony Williams' site. He's a well-known collector. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.

August 28, 2008, 12:38 PM	#11
grymster2007 Senior Member Join Date: May 22, 2007 Location: In the oak studded hills near Napa Posts: 2,203	The cool thing about all this is that for my $18, not only did I get the 20mm cases, a whole bunch of .38SPCL, some .45 ACP and .44 magnum cases, but I also picked up three three calculators at the estate sale. Two of which are very nearly NIB HP 15C scientific calculators. Mrs. Grymster was giving me a hard time about the calculators, until we got home that is, and I demonstrated that they're worth between $300 and $400 each. I'm actually feeling guilty.... like I robbed somebody. __________________ grym

August 30, 2008, 09:19 PM	#14
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,390	I missed this... CH is not China in international lingo, normally. CH is Confederation Helvetica. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.

August 31, 2008, 08:51 AM	#16
Mach II Sailor Junior member Join Date: March 22, 2007 Posts: 480	grymster, your 20mm cases, in my OPINION are definitely NOT made for any American 20mm gun, the 20mm rounds in my collection (i have 8 of the "old" 20mm, and none look like yours) have necks for the projectile and the rims are NOT rebated.

August 31, 2008, 09:47 AM	#17
Tombstonejim Senior Member Join Date: October 22, 2007 Location: Tombstone Az Posts: 202	Look here the british version had a shorter case for some reason. Gun Characteristics Designation USA: 20mm/70 (0.79") Marks 2, 3 & 4 British: 20mm/65 (0.79") Mark II Ship Class Used On Almost all Date Of Design about 1939 Date In Service 1942 Gun Weight 150 lbs. (68.04 kg) (including breech mechanism) 46 lbs. (20.865 kg) (without breech) Gun Length oa 87 in (2.210 m) Bore Length 55.1 in (1.400 m) Number Of Grooves 9 Length Of Rifling N/A Chamber Volume N/A Rate Of Fire 450 rounds/minute per barrel

August 31, 2008, 11:19 AM	#18
jrfoxx Senior Member Join Date: August 20, 2004 Location: Evanston,WY Posts: 898	Neat find, Grymster2007. Also, I'd LOVE to get a hold of one of those 57x441R shells in Mike Irwin's pic there. That thing has to be huge, and quite impressive/imposing looking. __________________ Q: How can I reduce the amount of mail I receive from the NRA? A: Simply email us at [email protected] or dial 800-NRA-3888 and request to be placed on the "Do Not Promote" list.

August 31, 2008, 02:00 PM	#19
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,390	Mach II, What years are stamped on your case heads? The Navy, in the 1950s, adopted a different 20mm that had a different case style, and also used a somewhat shorter case; 20x102mm Vulcan. If I'm not mistaken, that 20mm is now the same type that is used in Navy and Air Force gatling guns on air craft and also the guns that armed Cobra helicopters. The markings and dimensions are correct for a WW II 20mm shell in US service. If you look at this picture, the third one is the modern Vulcan; the fourth one is the 20x110mm Oerlikon as used by the Navy during WW II. You'll have to click the link. http://tinyurl.com/6xm4ff It decided has a rebated rim, a longer, shallower shoulder, and virtually no neck. Given the markings on Grymster's case, it's definitely a WW II Navy Oerlikon gun round. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.

August 31, 2008, 02:03 PM	#20
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,390	Tombstone, The British round didn't use a shorter case. The 20mm/70 and 20mm/65 means that the barrel in the American gun was 70 calibers (70x20mm) long. The British gun had a barrel that was 5 calibers shorter. That puts the American gun with a barrel of just shy of 5 feet. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.