The T31 was John Garand’s last project during his employment at Springfield Armory. It was proposed in 1948 as a bullpup configuration rifle to minimize muzzle blast and flash. It was a select-fire rifle with a 20-round detachable box magazine and basically every aspect of the design was unorthodox. The original gas system was more pneumatic than anything else, with the whole handguard tube filling with gas when it cycled. The recoil spring is a clockwork type in the buttstock, and the bolt uses a tilting wedge to lock.
At initial testing it ran into reliability problems after 2300 rounds. Upon disassembly, the found nearly an entire pound of powder fouling in the gas tube. This led to the gun being rebuilt with a tappet type gas system, and that’s the gun we have today to look at. Only two examples were made before Garand retired in 1953, and nobody took over the project when he left.
Thanks to the Springfield Armory National Historic Site for giving me access to this truly unique specimen from their reference collection to film for you! Don’t miss the chance to visit the museum there if you have a day free in Springfield, Massachusetts:
https://www.nps.gov/spar/index.htm
“(…)bullpup configuration rifle to minimize muzzle blast and flash(…)”
Longer barrel will help for that, but would not it be easier to put muzzle device for that. Cones for that should be known to U.S. technical intelligence in 1948 as there were used at Imperial Japanese Army Type 99 machine guns during WW2.
“(…)original gas system was more pneumatic than anything else, with the whole handguard tube filling with gas when it cycled(…)”
This looks to be more complicated variant of one used in Colt Model Potato Digger (with tunnel for gases as opposed to directly actuate mechanism in Potato Digger)
“(…)spring is a clockwork type (…)”
For another fire-arm exploiting this technology see Kretz rifle https://guns.fandom.com/wiki/Kretz_rifle
“(…)fouling in the gas tube(…)”
Another case of Garand assumption w.r.t. ammunition failing. Earlier one was Garand Model 1919 https://guns.fandom.com/wiki/Garand_Model_1919 which relied on maximal strength which primer could sustain.