The last gun Garand worked on before retirement was the T-31 Bullpup. From the Springfield Armory website …
U.S. RIFLE GARAND T31 “BULLPUP” .30 (T65E1) SN# 2
Manufactured by Springfield Armory, Springfield, Ma. – Limited prototype experimental select-fire weapon shoulder weapon; never went into production. Lightweight, selective full and semiautomatic rifle with an in-line stock in an attempt to reduce recoil. Cyclic rate of fire 600 rpm. Weapon weighs approximately 8.7 lbs. without accessories. Handguard cooled by circulating fresh air. German FG42 rear sight. Rubber stock and handguard. This was the last model worked on by John Garand.
What is especially interesting about this gun is the recoil system. The tube that surrounds the barrel is not a handguard but gas tube (I use the term lightly). A small around of gas deflected by the muzzle brake would enter the tube causing a shockwave to ripple down the tube towards the receiver end where it would actuate a piston. The system did not work very well because the tube would accumulate 3 grains of dirt for every shot fired!
Garand retired before the second version of the rifle was complete and so the project was terminated. The legacy of this rifle can be seen in the magazine design which was adopted for the M14 rifle.
[ Many thanks to Sven (Defense and Freedom) for emailing me the the info. ]