Two of the scarcest and least known of John Pedersen’s designs are the Model GY and GX rifles, which are basically copies of the production model of the M1 Garand. After losing out in the Army rifle trials with his toggle-locked rifle design, Pedersen made one last attempt to garner a US military contract by building his own slightly modified version of the M1. It function the same way as the Garand, with a long-stroke piston, gas port right by the muzzle, and rotating bolt. However, Pedersen put some of his own touches on the rifle, including spiral barrel fluting, drain/cooling slots on the underside of the stock, and a rotating drum to adjust elevation on the rear sight.
Less than 10 of the GY and GX rifles were ever made, and they (obviously) failed to make a significant impression on the US Army – they never went into any type of serial production. This one at Rock Island (#5 GY) is in magnificent condition, and still full of cosmoline from when it was put in storage.
One interesting question I have been unable to answer is, what is the difference between the GX and GY? The folks I have spoken to who have owned or handled one or both have been unable to point to any significant difference. The two designs do have separate serial number ranges (#3 GY and #3 GX are both documented), so it wasn’t just a change in nomenclature after a few were made. One possibility that does not seem to have been tested by anyone is that the two designation use different types of en bloc clip. Perhaps one uses the standard M1 clip and the other uses a clip design Pedersen thought to be better?
I do have this one diagram of a GX (not a GY), which Rock Island dug up. It doesn’t prove anything, but if you look at the clip drawn in the action, it is a Pedersen type, not a Garand clip: