Perhaps the most difficult part of the M1 Rifle to mass produce was the operating rod, or op rod. Its design was a consequence of John Garand's conviction that a successful military semiautomatic rifle needed the power of a full stroke, gas impingement operating system for reliable functioning under all combat and climatic conditions. At the same time he had to minimize the effect on aim of the gas system's reciprocation.
Thus, the original "gas trap" system of the first Garands (up to Serial Number circa 50,000) was designed to ensure that the bullet had left the muzzle prior to any action parts moving; consequently, the original gas trap Garands are reputed to be the most accurate of all service grade (non-accurized) M1s. As this arrangement was found to be deficient in strength, particularly when the bayonet was attached, and to carbon up over time thus reducing its effectiveness, the "gas port" system familiar to all M1 enthusiasts was born. With the gas port now some inches behind the muzzle the operating rod began to move before the bullet left the muzzle, but measurements on an M14 with an M1 gas system indicate the op rod moves only about .03" by the time of bullet exit. The comparable figure for the T44 (M14) with gas cut-off and expansion system was .05".
So we see the reason for the length of the M1's op rod. The reason for its curvaceous beauty was to bring it from near the muzzle around the barrel and up to the bolt, where it operates the action proper. The op rod is made in two parts, the tube and the handle. They are then welded together to create the completed component. During WWII the right angle joint where the two pieces came together proved to be a stress riser; thus after the war op rods from rifles under rebuilds were given a stress relief milling cut (the shape of a racetrack) in that area. If it's there it's obvious when you're looking at the drawing number. When M1 production resumed in the '50's all the op rods from all three manufacturers were made with this stress relief cut from the start.
Uncut rods are not the best idea for shooting, but are necessary for collectors' restorations. If your shooter has an uncut rod, hang it on the wall or sell it to a collector and use a good cut rod.
Actually, no op rod was really "problematic"; the WWII op rods would crack after a great deal of use & abuse, at the right angle where the handle goes to meet the tube; that's why the stress relief cut was ordered & why most WWII op rods have been "cut."
Post WWII, all op rods were made with the stress relief radius "built in." D35382 (no rev number) and all the "65" and "77" prefix rods are so made.
The final op rod design is that with drawing number 7790722-RA (Remington Arms) or -SA (Springfield Armory). I like to call it the "77" op rod, but as it is often found stamped "NM" it is widely known as the National Match op rod. It had a subtle change to the tube's curve to fit it somewhat more tightly around the barrel. This design was originally intended for and used in the building of Type 2 National Match rifles at Springfield. When the supply of good op rods dried up, this design was used for general rebuilds in the '60's. Quite a few went to Korea and have come back again as parts and on rifles. You'll see them both with and without the "NM" marking, but the rods are identical nonetheless.
One of the most skilled trades at Springfield Armory and the other M1 manufacturers was "rod bending" to the standard guage. Those who did this job well were highly regarded for their abilities.
For those of you who might have wondered, that "special jig" in the Navy Van at Camp Perry is the op rod gauge! It was used to check the many critical areas & bends of the M1 Garand op rod. It was not used to bend 'em, just to check 'em.
It was possibly the most incredible gauge ever made to gauge a part for a U.S. Service Rifle. The cost to make such a thing is mind boggling. Such extravagence in gauging reached its zenith with the Garand in general, and this one in specific! The Garand even had a gauge to measure serviceability of the op rod spring tension. Sheesh, just put a new spring in her! Springfield Armory, (the original of course), could have bought tens of thousands of new springs for the cost of just one of these gauges, not to mention the time required to test each spring.
I'd encourage all of you who attend the DCM/CMP Highpower Service Rifle phase to go & ask the Navy Van to see this gauge. It's a real wonder.
Lastly, the silver "button" on the end of the op rod is the gas piston. It should be at least .525" in diameter and within .00035" of round. Max dimension is .526".
--Walt Kuleck & Clint McKee