kellyfamille
Recruit
- 4
- Jun 20, 2024
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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 thanks very much for this info.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
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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
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Paul3 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
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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
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.Hence our assumption that they have been ejected from a B-25 overflying the area.
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.
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 - WikipediaHey 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.