B-25G and B-25H information on spent 75mm cartridges - through hatch or port?

[kellyfamille]

Looking at the operation of the 75mm in both the B-25G and B-25H how did the gunner remove or secure the spent casings? Were they ejecetd through a port or secured somehow in the ammo rack or other container?
Any help on this would be great.
Kellyfamille

 

[Micdrow]

Looking at the operation of the 75mm in both the B-25G and B-25H how did the gunner remove or secure the spent casings? Were they ejecetd through a port or secured somehow in the ammo rack or other container?
Any help on this would be great.
Kellyfamille

Orginially the spent cartriges where ejected out of the plane but after a cartrige hit another B-25 the practice was discontinued and spent cartriges where put back in the rack and unloaded after the plane has landed. Below picture of the ejection system from the book B-25 Mitchell The Magnificent Medium by N.L. Avery

Cannon Ammunition Storage Rack
A retainer in the upper rack held the noses of the rounds, and a selective lock in the lower of the rack secured their bases. The retainers could be inserted into three positions to accommodate the different lengths of the armor piercing, high explosive and smoke shells. The rack is capable of holding 21 shells. Used shell casings are returned to the rack once fired and disposed of later on the ground.

Pictures below of case

 

[Micdrow]

3 pages from the Flight manual of a B-25G on how to fire the 75mm cannon. I think that answers all your questions

Have a great day

Paul

 

[kellyfamille]

Orginially the spent cartriges where ejected out of the plane but after a cartrige hit another B-25 the practice was discontinued and spent cartriges where put back in the rack and unloaded after the plane has landed. Below picture of the ejection system from the book B-25 Mitchell The Magnificent Medium by N.L. Avery

View attachment 784699

Cannon Ammunition Storage Rack
A retainer in the upper rack held the noses of the rounds, and a selective lock in the lower of the rack secured their bases. The retainers could be inserted into three positions to accommodate the different lengths of the armor piercing, high explosive and smoke shells. The rack is capable of holding 21 shells. Used shell casings are returned to the rack once fired and disposed of later on the ground.

Pictures below of case

View attachment 784702

View attachment 784703

Micdrow thanks very much for this info.

 

[kellyfamille]

3 pages from the Flight manual of a B-25G on how to fire the 75mm cannon. I think that answers all your questions

Have a great day

Paul

View attachment 784705View attachment 784706View attachment 784707

Paul
yes thanks this answers my query. Just FYI this comes about due to a surface find of a 75mm cartridge (M-18) near the north coast of Papua New Guinea (Buna-Gona area). The only reasonable explanation seems to be it was from a B-25.
Best Regards

 

[Micdrow]

Paul
yes thanks this answers my query. Just FYI this comes about due to a surface find of a 75mm cartridge (M-18) near the north coast of Papua New Guinea (Buna-Gona area). The only reasonable explanation seems to be it was from a B-25.
Best Regards

Morning,

Could have been thrown over the side of a B-25 that was damaged in combat or mechanical failure. It was comnon place to throw out everything possible to make it back to base once out of the combat area to keep the aircraft as long as possible.

Love to see some photographs of the casing.

All the best

Paul

 

[MIflyer]

The spent shell casings for the B-25G no doubt rattled around on the floor until the poor "gunner" (Navigator) had time to do something with them.

Read of one such mission in the Med. Of course the pilot wanted to get off as many rounds as possible during each pass and kept telling the navigator to load them faster. Finally, disgusted at not being able to hit much of anything, the pilot called for a course to head home. The navigator, stripped to to the waist, sweating profusely, and stumbling over the shell casings replied, "Fly, West, sir." The pilot responded that was not a proper course. The navigator went to his table, examined some maps, measured a course, and replied, "Don't fly West, sir. Fly 270 degrees."

The B-25H had a lighter version of the cannon, the T9, and it seemed to be sort of semi-automatic and could fire faster. The book "B-25 Mitchell The Ultimate Look" has extensive information on the cannon installation and procedures.

 

[kellyfamille]

Dear All,
Thanks for the information above.
I attach photos of the spent 75mm shell showing the head stamp for those interested.
Our research suggests it may be of Canadian manufacture under licence to the US.
Also shown is the current museum label describing the casing.
It is currently in the Kienzle Museum at the small town of Kokoda, Oro province, Papua New Guinea about 80km from the north coast.
It was found on the surface near Kokoda but as the label states no 75mm guns were used by the Australians in the Kokoda campaign. No US combat forces served in the area.
Hence our assumption that they have been ejected from a B-25 overflying the area.
Regards

 

[ThomasP]

Hey kellyfamille,

FWIW

The 75mm M18 series cartridge case (75x350R) was not compatible with the M1 75mm Pack Howitzer. The Pack Howitzer used the 75mm M5 series of cartridge case (75x272R) as opposed to the M18 series. The '350' and '272' are the lengths of the cartridge cases in mm.

However, (leaving out the US made 75mm gun tanks and gun motor carriages) the 75mm M18 series of cartridge case was used with the various US manufactured 75mm field guns based on the French M1897 as well as with the British 75mm gun armed variants of the Churchill Mk VI & VII and Valentine Mk IX.

I do not know if the Australian forces used the 75mm field guns, and I do not think they received any of the Valentines with the 75mm, but they did test the 75mm armed Churchill and Sherman tanks in PNG (Wiki says the tests were performed in the Madang area). Also, the Australians used the 75mm armed Churchills after the war.

 

[MIflyer]

Hence our assumption that they have been ejected from a B-25 overflying the area.

The B-25 book says that initially the crews were told not to dump their empty shells out of the aircraft to prevent the Japanese from finding out about that armament. The 75MM was effective against ships and they would not have wanted the Japanese to know they could be hit by a 75MM.

 

[ThomasP]

Hey Myflyer,

re

The B-25H had a lighter version of the cannon, the T9, and it seemed to be sort of semi-automatic and could fire faster. The book "B-25 Mitchell The Ultimate Look" has extensive information on the cannon installation and procedures.

As far as I know the 75mm in the B-25 was never equipped with an autoloader. The M9 (T15E1) was fitted to the XP-58 and possibly the XA-26 prototype. There may have been some other prototypes fitted with an autoloader also. Maybe it was tested experimentally in the B-25?

The original 75mm fitted in the B-25 was based on the 75mm M3 tank gun. The tank version had what was called a 'semi-automatic' breech block. For anyone not familiar with the action on a semi-automatic breech block equipped gun, the breech block opened automatically via a cam during the recoil of the barrel. The breech then stayed open during the return forward to battery position and the case was ejected backwards out of the chamber via cam mechanism operating the ejector pins. The breech block would remain open until the loader inserted a fresh cartridge and as the case became seated in the chamber the casing would trigger a mechanism that closed the breech block.

The first variant of the 75mm gun used in the B-25 was modified and (for a reason I have not found any specific information on) lost the semi-automatic breech block capability. To open the breech and eject the spent casing the loader (cannoneer) had to manually pull the breech opening lever, whereupon the ejector pins were also activated and the case was ejected. He would then insert the fresh cartridge, and push the breech opening lever to close the breech.

The second variant of the 75mm used in the later production 75mm gun armed B-25 variants regained the semi-automatic breech block capability.

I think the above is correct.

 

[MIflyer]

Supposedly the 75MM gun was an actual option for the A-26, as illustrated below; note the autoloader. But since in combat with the B-25 it was found not to be much good against anything but non-combat ship targets and was phased out well before the end of the war. In the B-25H they even added a gunsight radar to help with the range estimation problem.

 

[pinehilljoe]

I remember an old Wings/Airpower article on the B-25, a pilot was interviewed and said he thought the 75mm was more accurate than rockets.

 

[pinehilljoe]

Hey Myflyer,

re


As far as I know the 75mm in the B-25 was never equipped with an autoloader. The M9 (T15E1) was fitted to the XP-58 and possibly the XA-26 prototype. There may have been some other prototypes fitted with an autoloader also. Maybe it was tested experimentally in the B-25?

The original 75mm fitted in the B-25 was based on the 75mm M3 tank gun. The tank version had what was called a 'semi-automatic' breech block. For anyone not familiar with the action on a semi-automatic breech block equipped gun, the breech block opened automatically via a cam during the recoil of the barrel. The breech then stayed open during the return forward to battery position and the case was ejected backwards out of the chamber via cam mechanism operating the ejector pins. The breech block would remain open until the loader inserted a fresh cartridge and as the case became seated in the chamber the casing would trigger a mechanism that closed the breech block.

The first variant of the 75mm gun used in the B-25 was modified and (for a reason I have not found any specific information on) lost the semi-automatic breech block capability. To open the breech and eject the spent casing the loader (cannoneer) had to manually pull the breech opening lever, whereupon the ejector pins were also activated and the case was ejected. He would then insert the fresh cartridge, and push the breech opening lever to close the breech.

The second variant of the 75mm used in the later production 75mm gun armed B-25 variants regained the semi-automatic breech block capability.

I think the above is correct.

I thought the 75mm used in the B-25 was the M-6 version. This gun was used in the M-24 Chaffee and adapted for the B-25. Edit: it was the M5 version: 75 mm gun M2–M6 - Wikipedia

 

[ThomasP]

This is the cover from the maintenance manual TM 9-1311 (there is also another manual TM 9-311) covering the early 75mm used on the B-25.

The 75mm used on the later B-25s was the M5 (aka T13E1). As you say the M5 was based on the 75mm gun used in the M24 Chaffee light tank. The manuals for this model are TM 9-1312 and TM 9-312 75mm Gun M5 and Airplane Mount AN-M9, along with the early pre-standard TM 9-312 75mm Gun T13E1 and Aircraft Mount T13E2.

I have the manual TM 9-1311 for the early 75mm Gun M4 but not the later manuals. I only have part of the T.O. for the 75mm Gun M5.