The US Firefly: Yeah I said US Firefly, They Made Some But None Saw Combat, And They Were Unique And Not Like The Brit Ones.
Before the Normandy landings, the British had offered the US up 200 guns a month, if they were interested in the 17 pounder gun. Their rearmament program was well underway and would have enough Firefly tanks ready to go by D-Day. The US was not interested for a variety of reasons. The 76mm M1A1 and M3 90mm gun programs were well underway. Vehicles that used the guns were in the pipeline, even if there wasn’t much demand from the field yet. They did not want to complicate the supply situation with another tank ammo type.
Another reason was the 17 pounder did not really impress the US officers who witnessed test of it. It had both a large muzzle-flash and breach flashback, that hinted to them of a poor design. The efforts to convince the Americans of the errors of their ways went dormant along with the program. It wasn’t until the Ardennes offensive, when the US faced some heavier German armor, and in larger numbers than thought to be possible, that the program came back to life.
Conversions of 75mm armed US Sherman took place starting in March of 45. The US conversions were different in a few ways. The armored box on the rear of the turret was a little bigger to fit US radios, and the M2 machine gun brackets were welded to the end of the radio box. The tanks chosen for the conversions were all M4s and M4A3. It’s possible some large hatch final production Shermans with all the improvements were a part of the 160 to 200 that were converted before the program was suspended.
No one has come up with what happened to the tanks, and it seems like none survived. None were ever issued to US units, it’s one of those little mysteries lost to the archives and or time.
Sources: Armored Thunderbolt by Zaloga