The Winchester G30R is the final iteration of David Marshall Williams’ work on a full power .30 caliber military rifle. The project began with a design by Ed Browning (John Browning’s half brother) using a tilting bolt an annular gas piston, manufactured for US military trials by Colt. It moved to the Winchester company, which assigned Williams to the project when Browning died in 1939. Williams first replaced the annular gas piston with his gas tappet system, creating the G30M rifle. This performed poorly in trials, and the next iteration was the replacement of the tilting bolt with a Garand-type rotating bolt, creating the Winchester M2 rifle.
The US military was not interested in the M2 in .30-06, but thought the concept could be ideal for the Light Rifle trials then underway, and Winchester scaled it down to .30 carbine, and won the Light Rifle trials with it. That weapon would go on to become the M1 Carbine. Once it was in mass production, Winchester returned to the M2 design and improved it into this G30R. It was tested by the Marine Corps, but not adopted. The Canadian military also expressed an interest, but the US government opted to not allow any exports, and so Canada never tested it.
The US Army was quite satisfied with the M1 Garand, but suggested that this rifle might be made into a replacement for the BAR if it were redesigned a bit for greater sustained fire capacity. Winchester did so, creating the Winchester Automatic Rifle (WAR), which was on track for adoption until World War Two ended and immediate arms development became a much less important priority for the military.
Thanks to the Institute of Military Technology for allowing me to have access to this rifle so I can bring it to you!