On the subject of mounting the 76 mm M1 L/53 into the original M4 turret, a question pops up:
“If the original M4 turret was used to test an even longer 76 mm T1 L/57, why didn’t tank crews in the field attempt to replace their Sherman’s 75 mm with surplus 76 mm guns, considering it worked anyway?”
Well… They did.
In February 1945, Patton’s Third Army Ordnance unit conducted a field modification involving an M4A3(75) to use a 76 mm gun as a part of large-scale tank rearmament plan. However, there were several issues in regards to this field conversion:
First, the 75 mm M3 weighed 405 kg, while the 76 mm weighed 517 kg. This increased the weight required for the turret to balance.
Second, the gun mounts of both guns are not exactly the same. The M34A1 gun mount was used for the 75 mm and the M62 was used for the 76 mm instead. The latter was adapted for the T23 turret with its box-shaped mantlet.
Much like the M4A1(76M1) prototype, this conversion, let’s call it M4A3(75)W w/ 76 mm M1, involved modifying the M34A1 gun mount to accept the 76 mm M1 gun breech, as well as welding an additional slab of steel at the rear of the turret to act as a counterweight. While feasible, the turret was still cramped compared to a dedicated 76 mm-armed tank using the T23 turret. Also, by the time this conversion took place, new batches of M4A3(76)W were already arriving in large numbers to the frontline, deeming this field modification redundant. What happened to this field modded vehicle remains unknown, but it was most likely returned back to its original M4A3(75) configuration, and the 76 mm gun sent back to depot.
As there were surplus 76 mm guns being sent alongside the M4A3(76)s as spare parts, those were instead allocated to rearm existing M4A3E2(75)W assault tanks, with about 100 tanks converted as M4A3E2(76)W, almost half the entire units manufactured and sent to the battlefield. This conversion proved to be much more successful. The secret lies within the Sherman Jumbo’s own gun mount, the T110. This gun mount is basically a fully intact M62 gun mount welded with additional 88.9 mm of heavy steel plate, effectively resulting in a tandem mantlet with double the thickness of 177.8 mm, while capable of mounting a 76 mm gun.
There is one instance where this tank is portrayed to the extreme in an RTS game, called Company of Heroes. The M4 Sherman’s in game model has two configurations whether the 76 mm M1A1C upgrade has been purchased or not. One is the original M4(75), and the other is the same M4(75) retrofitted with the 76 mm M1A1C gun. The model is surprisingly similar to the field modded M4A3(75) w/ 76 mm M1, except with the absence of the counterweight plate at the rear turret. Although it’s understandable why this decision was taken, considering this game came out in 2006, and still handicapped with technical limitations at the time. Changing the entire M4 turret to the T23 turret when upgrading to 76 mm would be bothersome, while swapping the 75 mm with 76 mm was much simpler instead. This was fixed with the community-made mod called Blitzkrieg Mod, where both Sherman 75 and Sherman 76 are properly separated.
This vehicle is not a part of MDAP Sherman, a U.S. program to throw some retrofitted Sherman 75 with 76 mm gun for allied countries, even though the concept is similar. The difference is that the MDAP program only began post-WWII.
Steven J. Zaloga – Armored Thunderbolt: The U.S. Army Sherman in World War II