M4A1 76mm sherman

M4A1s were being phased out in the US army due to being hard to field repair and the cast armor being slightly softer than regular armor
but the first long gun shermans to arrive in europe used the M4A1 as the basis, because they had been produced much, much earlier in january 1944 before the preferred M4A3 was still in wide service

the long gun came with an equally long sight, a 5x telescopic sight and a 6x periscope