17 Pdr Question

The 17 pounder was the same gun in both tanks so the barrel lengths were the same. If the lengths are different it is probably due to how the gun was mounted in the turrets of each tank.

It is partly an illusion, and partly the different mount. The M10 had more room in the turret, and the gun was mounted a bit further back in relation to the trunions to fit the cradle in behind the mantlet due to the design of the turret front, making it tail-heavy, so to balance it they needed extra weight on the front. The Firefly, by comparison, had to be modified with a shortened mount because there wasn't enough room in the turret for normal recoil distance back from the Sherman trunions - hence the gun was "pushed forward" in its new cradle and was actually nose-heavy. (They solved this by making the breech slightly bigger during the redesign...) This means more of the barrel sticks out from the front of the Firely mantlet, even though both guns were the same total length from muzzle to back of breech. Naturally, the Firefly-specific mods to the barrel and breech meant they were not interchangeable with M10C tubes.

I don't think the Achilles had a stabiliser, and I thought they were removed from Fireflies during conversion, but would need to check. I recall reading that most Sherman crews turned them off anyway, as they were more work than they were worth...