M
British Ordnance Collectors Network
This is a sample guest message. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!
3 inch case confusion
U.S. 3 inch cases can be divided into two types, Navy (3 inch 50 Cal.) and army. There were 2 chamber lengths for the Army antiaircraft guns, and each had 2 slightly different case lengths due to the size of the rotating bands of the projectiles. The older projectiles from WWI late development (Shrapnel and MK 1 HE, etc.), had smaller bands, so the cases were longer for these rounds, as the chamber length went from top of rotating band to base of case. So, there are 2 case lengths and designations for the long chamber guns for fixed AA gun mounts and 2 case lengths and designations for the short chamber guns which were the mobile AA guns and the M10 open topped tank destroyer.
Case descriptions are as follows: For 3 inch AA fixed mount guns, the tallest cases are the MK 1 and MK 1A1 at 27.15 inches long, the difference between numbers being primer type. These cases were used for the shrapnel and any other older projos having a small (.5 inch high) rotating band. For the more modern projos, HE M42 and MKIX, AP Shot, and APCBCT M62, the two cases MK1 M1 and MK1 A1 were shortened up to 26.7 inches.
For 3 inch AA mobile mount guns, the longer variations for old projectiles, the MK II and MK IIA1 cases are 23.65 inches long. The cases for the newer design projos, the MKII M1 and MKII M2 are 23.08 inches long. This is your case, and it could have been used in the AA gun or the M10 tank destroyer. All of these cases can be found in brass, and there are very few remaining examples of laquered steel cases which would be MKII M2B1. In the U.S., a B1 designates a steel case.
Your case should be 3 inch inside diameter at the mouth. I hope this helps.
U.S. 3 inch cases can be divided into two types, Navy (3 inch 50 Cal.) and army. There were 2 chamber lengths for the Army antiaircraft guns, and each had 2 slightly different case lengths due to the size of the rotating bands of the projectiles. The older projectiles from WWI late development (Shrapnel and MK 1 HE, etc.), had smaller bands, so the cases were longer for these rounds, as the chamber length went from top of rotating band to base of case. So, there are 2 case lengths and designations for the long chamber guns for fixed AA gun mounts and 2 case lengths and designations for the short chamber guns which were the mobile AA guns and the M10 open topped tank destroyer.
Case descriptions are as follows: For 3 inch AA fixed mount guns, the tallest cases are the MK 1 and MK 1A1 at 27.15 inches long, the difference between numbers being primer type. These cases were used for the shrapnel and any other older projos having a small (.5 inch high) rotating band. For the more modern projos, HE M42 and MKIX, AP Shot, and APCBCT M62, the two cases MK1 M1 and MK1 A1 were shortened up to 26.7 inches.
For 3 inch AA mobile mount guns, the longer variations for old projectiles, the MK II and MK IIA1 cases are 23.65 inches long. The cases for the newer design projos, the MKII M1 and MKII M2 are 23.08 inches long. This is your case, and it could have been used in the AA gun or the M10 tank destroyer. All of these cases can be found in brass, and there are very few remaining examples of laquered steel cases which would be MKII M2B1. In the U.S., a B1 designates a steel case.
Your case should be 3 inch inside diameter at the mouth. I hope this helps.
If your case is only 275mm long, it must have been cut down. This would explain the apparant 89mm size.
Hello Hazord,
From the date on this thread I am arriving to it later than to Osama Bin Laden's burial, but your clarification of the differences between
the various types of 3 inch, 75mm, and 76 mm American ordnance is as IN DEPTH as anyone has ever made it plain to me, and has clarified things
to a significant degree.
A while back, a fellow collector here in the US sold a rare article at auction I will put up so you can view and comment on it. I am a long time collector
of "things in the 3 inch-76mm size" yet I have never had a clear exposition of all the specifics of the types and services they were made for.
I had never realized that two services ( both Army and Navy ) were making differing sized ammunition for weapons that were varying only slightly, but apparently they were not interchangeable and were used for entirely different purposes from anti-ship, anti-tank or anti-aircraft applications. All this got very confusing,
and just when I think I have it sorted out, a new type emerges and opens the wound again.
So, I will put up these two pictures which were the two the seller used for the auction, and allow you to specify which of these it might have been. I think I used this picture in another post a while ago, but I cannot find it.
Thanks,
Walt
From the date on this thread I am arriving to it later than to Osama Bin Laden's burial, but your clarification of the differences between
the various types of 3 inch, 75mm, and 76 mm American ordnance is as IN DEPTH as anyone has ever made it plain to me, and has clarified things
to a significant degree.
A while back, a fellow collector here in the US sold a rare article at auction I will put up so you can view and comment on it. I am a long time collector
of "things in the 3 inch-76mm size" yet I have never had a clear exposition of all the specifics of the types and services they were made for.
I had never realized that two services ( both Army and Navy ) were making differing sized ammunition for weapons that were varying only slightly, but apparently they were not interchangeable and were used for entirely different purposes from anti-ship, anti-tank or anti-aircraft applications. All this got very confusing,
and just when I think I have it sorted out, a new type emerges and opens the wound again.
So, I will put up these two pictures which were the two the seller used for the auction, and allow you to specify which of these it might have been. I think I used this picture in another post a while ago, but I cannot find it.
Thanks,
Walt
I did some looking around yesterday after making this post, from what I could determine, the relative performance of the M-10 ammunition and the performance of the 3"-50 Navy gun seem to have been just about the same, with a muzzle velocity of about 2600-2700 feet per second for both guns.
I don't have access to in-detail energy and muzzle velocity characteristics of both types ( Army and Navy ) but would you agree that the two different types of
guns had similar performance with similar projectiles being thrown?
Also, how was this round in defeating the heavier tanks such as the Panther and Tiger? Could it punch thru the glacis or mantlet at 500 yards or more? This kind of info is not readily available, but I have seen wartime test data on various guns from the 57mm to the 90mm done on the spot with knocked out German tanks.
Thanks
Walt
I don't have access to in-detail energy and muzzle velocity characteristics of both types ( Army and Navy ) but would you agree that the two different types of
guns had similar performance with similar projectiles being thrown?
Also, how was this round in defeating the heavier tanks such as the Panther and Tiger? Could it punch thru the glacis or mantlet at 500 yards or more? This kind of info is not readily available, but I have seen wartime test data on various guns from the 57mm to the 90mm done on the spot with knocked out German tanks.
Thanks
Walt
There was some penetration data available on the 3 inch army gun, but Navy info is scarce. Rule of thumb on Navy APCapped ammo is that it will penetrate it's diameter, but that is for the larger rifles like 6 inch through 16 inch. And you have to take into account that the penetration data was held back as confidential during the war. In reality, the U.S. was behind the Germans and U.K. in WWII because they had very few HEAT projectiles and no source of Tungsten for penetrators. The best antitank round that any of the Allies had was the U.K. 17Pdr APDS with Tungsten core. It would penetrate frontal plates on Panther tanks better than anything else.
Shakey,
Honest to God, every 2.17 months someone writes in about these 3 inch and 76mm casings and projectiles. I have been lucky enough to have collected them over the years along with the documentation, and can see the differences in them so I can explain. I understand how confusing it can be. The shrapnel projectiles are the other confusing part of the equation.
If you really want a headache, try figuring out all the 75mm casings from WWI and WWII. 3 inch stuff is cake compared to the bazillion 75mm variants.
Honest to God, every 2.17 months someone writes in about these 3 inch and 76mm casings and projectiles. I have been lucky enough to have collected them over the years along with the documentation, and can see the differences in them so I can explain. I understand how confusing it can be. The shrapnel projectiles are the other confusing part of the equation.
If you really want a headache, try figuring out all the 75mm casings from WWI and WWII. 3 inch stuff is cake compared to the bazillion 75mm variants.
Last edited:
No kidding Hazord. This started for me trying to figure out a 17pdr apc projo and led back to the former cases, 77mm, 76mm cases to the 3"/50, the 600mm long AA 98-02-18 coastal and all mixed up like that.:smile: Im glad someone else has gone through it to make some sense of it all. Would you happen to have any examples of 3"projectiles for the wolverine or somewhere to see these types? Thanks,Shaky.
Shaky,
There are a metric butt ton of posts here on 3 inch and 76mm projectiles and cases. First of all good books to visit are TM 9-1901 Artillery ammunition 1945 and TM 9-1904 Ammunition Inspector's Guide 1944. It has all the seacoast and AAA descriptions of case lengths.
TM 9-1904 available for download here:
http://www.ibiblio.org/hyperwar/USA/ref/TM/index.html
TM 9-1901 is in 4 files here on BOCN I believe.
posts with projo data:
http://www.bocn.co.uk/vbforum/threads/80506-Would-this-be-a-75mm-or-76mm?highlight=seacoast
http://www.bocn.co.uk/vbforum/threa...-or-3-quot-Projectile?highlight=super+sherman
http://www.bocn.co.uk/vbforum/threads/46205-US-M62-AT-Projectile?highlight=super+sherman
http://www.bocn.co.uk/vbforum/threads/50661-3inch-M62-proj?highlight=super+sherman
http://www.bocn.co.uk/vbforum/threads/75869-3-inch-projectiles?highlight=inch
Hope it doesn't give you a headache. To clarify, the 76mm gun with straight case used the same projos as the one for the M10 tank destroyer. They were just labeled 76mm G instead of 3 G
There are a metric butt ton of posts here on 3 inch and 76mm projectiles and cases. First of all good books to visit are TM 9-1901 Artillery ammunition 1945 and TM 9-1904 Ammunition Inspector's Guide 1944. It has all the seacoast and AAA descriptions of case lengths.
TM 9-1904 available for download here:
http://www.ibiblio.org/hyperwar/USA/ref/TM/index.html
TM 9-1901 is in 4 files here on BOCN I believe.
posts with projo data:
http://www.bocn.co.uk/vbforum/threads/80506-Would-this-be-a-75mm-or-76mm?highlight=seacoast
http://www.bocn.co.uk/vbforum/threa...-or-3-quot-Projectile?highlight=super+sherman
http://www.bocn.co.uk/vbforum/threads/46205-US-M62-AT-Projectile?highlight=super+sherman
http://www.bocn.co.uk/vbforum/threads/50661-3inch-M62-proj?highlight=super+sherman
http://www.bocn.co.uk/vbforum/threads/75869-3-inch-projectiles?highlight=inch
Hope it doesn't give you a headache. To clarify, the 76mm gun with straight case used the same projos as the one for the M10 tank destroyer. They were just labeled 76mm G instead of 3 G
Last edited: