Sherman MkVc Firefly 17-pdr question

[James P]

In the confined space of a tank turret a horizontal breech makes complete sense as it allows full range of motion in elevation and depression of the gun.

[Mike Cecil]

I agree, and can see a number of advantages for a horizontal breech block, particularly with the block sliding away from the loaders position, which would then make the handling of the large 17-pdr round easier to move sideways into alignment with the chamber.

The elevation of the gun would be restricted by, among other things, the design of the mantlet/turret external interface and internally what is located beneath the downward swing of the breech. So with regard to internal room, it would depend on the turret basket depth and stowage design. Was this so cramped in the Sherman as to dictate the manufacture, in the middle of a war, of a different breech when the vertical sliding breech was already in production?

Mike

[Mike Cecil]

I've had another thought: what is the distance from the back of the 17-pdr breech block to the turret ring on a Sherman Firefly, compared to the length of the longest 17-pdr round?

Maybe that was the restricting feature - the extra 8 or so inches further back required to move a 17-pdr round into alignment with the chamber of a vertical breech, compared to a horizontal breech.

Thoughts?

Mike

[James P]

You also have to factor in the human fit and ergonomics, I think there is a bit more to making the machine fit the man (or man fits machine) then turning the 17 pdr gun by 90°, there is a stowage reconfiguration and no doubt the breech lever is different.

[Mike Cecil]

Hi James,

I'm sure it was not as simple as just the distance between breech ring and turret ring, but I have to start somewhere in getting to a better idea than just wiked-pedias blanket 'internal space considerations' and I don't have access to any of the original development reports.

Mike

[Jakko Westerbeke]

IIRC this has some answers: https://www.youtube.com/watch?v=__Y8YJeas4I though I don’t feel like watching all of it again to find them

[Mike Cecil]

Thanks Jakko, the visuals certainly provide some good information.

Mike