Well I was almost right;
Scott A. Duff Publications and Historic Martial Arms: T26, misnamed the 'Tanker Garand'
The M1 “Tanker” Garand Myth
The T26 "Tanker" has a 18" barrel.
The Shuff's Mini-G has a 16" barrel.
Notice the extra 2" piece of hand guard on the T26.