So when it first appeared in Normandy, the Sherman Firefly and it's meaty 17 pounder represented an ideal combo of reliable chassis, great gun and devastating firepower right?

Ummm...

Truth is a bit more complex. /1
#WW2 #SWW #History

Deliveries of Firefly to units only commenced in April 1944,
just a few weeks before Overlord & left minimal time for familiarisation.

Armoured Regiments mostly utilised Fireflies on a basis of 1 per troop of 4 tanks. /2

Finally each armoured regiment troop had access to integral, meaty, anti-tank firepower capable of dealing serious damage to any German AFV likely to be encountered. /3

The dual purpose 75mm gun was quite capable of laying down a reasonable HE shell or AP round for dealing with Panzer III or IV.

Firefly's 17 Pounder had.... problems with HE, but excelled at tank killing. So Tigers and Panthers would need to be wary. /4

Firefly's design history dated back to March 1943 when the General Staff published "Policy on Tanks" which effectively stated the majority of tanks should have a good HE weapon and...

[See image below] /5