I've been told (and raging debates started in other forums) that excessive load pressure can damage the operating rod on the Springfield M1 Garand.

Lot's of arcane references to "internal pressures" or "working pressures" "operating pressures."

I'm loading Hodgdon H-414 w/ 150 gr Winchester PP. Surplus, Lake City brass. I'm loading 57.7 gr. -- Max is listed at 58.0 for 3043 fps in a 26" bbl. with 48,7000 cup.

Hodgdon H-414 produces low pressures and high velocities. Yet I'm being told that powders like H-4895 which produce higher pressures and lower velocities are less likely to damage the operating rod on this gun.

Makes no sense to me. Does it make any sense to anyone else here?

Intresting question, may I take a stab at it ?
The manuals list 'Chamber' pressure what is of concern to Garand shooters is 'Port' pressure. IE: the pressure in the barrel when the bullet is about 1 inch from the muzzel.
The slower powders have lower chamber pressures but higher port pressure.
There is now on the market a gas cylender plug that has interchangable venting orfices that will limit the pressure on the piston (by venting the excess to the air)

The American Rifleman did a pretty extensive article on reloading for the Garand back a few years ago. Since I have a DCM Garand I kept the article. When I get home I will list the particulars of loads that fall within the burning range for the Garand.
There are a lot of powders that work well for a 30-06 that will tear up the Garand, so you have to be careful.

Its not the actual pressure range that cause problems in the Garand...its the speed of the propellant and the nature of the pressure curve. Fast and slow burning powders will cause problems. You want to use powders like IMR 4895...medium burning powders. AA2520 also does a good job. You'll want to avoid,like the plague, the slower powders like R22

Kentucky Nimrod is correct. Use powdeers with burning rates in the IMR 3031 to 4320 range, best being 4895, 4064, and similar-speed powders. One excellent target load is 47 grains of 4064 with the Sierra 168 grain HPBT Match bullet. Note H414 is getting a bit on the too-slow side for the M1.

H-414 is way too slow for the Garand, 2 proven loads are 46.5grs of 4895 with a 168gr, or 48grs of 4064, I've also had excellent results with N-202 48grs with the 168gr match bullet.

Thank you!

Tell me more. This makes sense, but I'm not ready to stop the discussion.

Sierra's Reloading Manual, p.428:
"When loading for a Garand, powders in the medium burning range must be used. Due to its system of operation, the Garand can be damaged by improper powder selection, even if the loads themdselves are perfectly safe.
We have had our best results in Garands when using IMR-4895, IMR-4064, 2495br and 2520."

Loading Guide 1 of Accurate, p.333:
"The loads shown below using the 150 and 168 grain bullet were developed with powders of the correct burn rate for the Garand's gas system to approximate the performance of the M2 Ball and M72 Match ammo."

A-Sqare's Any Shot you want, p.408:
"One major reason factories have have kept pressures down and used medium burning rate powders is the M-1 Garand. It is pressure sensitive at the gas port.. The slow burning powders have much higher pressures down the barreland this greatly increases the chances of a bent or sprung operation rod in a Garand."

In the March 1974 edition of The American Rifleman you find on p. 21 the illustration of a standard operation rod and of a M1E3 rod which ist by far stronger and replaces the standard rod since 1944.

J.Hatcher quotes in "The Book of the Garand", p.127, a report of the Chief of Ordnance to the Chief of Staff: "From the above sequence of events, extracted from the War Department, it is evident that the statement that the M1 ammunition is not suitable for use in the Garand rifle, the pressure being too great, thereby making it necessary for the Department to make M2 ammunition, has no foundation in fact. Each M1 rifle made is required to operate satisfactorily both M1 and M2 ammunition before it is accepted."
(Retired Bum explains the ammo in detail in www.hardcoretalk.com ).

In "Hatcher's Notebook", p.206, we find " In trying to determine the ultimate strength of the gun, Mr.Garand built up progressively higher proof loads in increments of 5000 pounds pressure, from the regular proof load of 70.000 lbs. to the extreme figure of 120.000 psi.
At this latter figure, cracked left lugs on the bolt began to be encountered. A gun in which the bolt had the left lug cracked by one of these excessive high pressure overloads was then fired an endurance test of 5.000 rounds of service ammuno, using the cracked bolt, which showed no further deterioration. The U.S. M1 Rifle thus has perhaps the strongest action of any military shoulder rifle in existence at this time (1947).�

As I believe Mr. Hatcher and Mr. Garand, I will not reproduce this test with my Garand.

I wonder if the op rod story is one of those shooting myths and ask: does anyone know someone to whom this kind of failure really ocurred ?

May I repeat my question - reality or myth : does anyone know of a op rod failure caused by a wrong charge ?

As there was no answer to this question yet, I tend to believe it's a myth.

Thank you.

Bent op rods are a fact. I've seen it happen (not to my gun) and if you go to a gun show and look at used Garand parts you will find them with regularity. They are caused by the slow burning powders, which again, are safe from a SAAMI spec standpoint and also safe from "the gun's not going to blow up" standpoint. But because the slow powders develop their peak pressure just as the bullet passes the gas port, the op rod is subject to much harder port pressure and generates more operating velocity than the normal speed generated by the medium burning powders. The op rods get pounded and eventually gets bent/unserviceable.
Its not unsafe in any sense of the word but it will make your gun unserviceable until you go out and buy a new op rod which now generally run over $100...
IIRMC, the early grenade launchers also caused similar problems (bent op rods) as the propelling cartridge had a big charge of very slow propellant. The second generation grenade launchers for the M1 Garand solved this problem by installing a device which effectively closed the gas port. I'll have to dig out my copy of Hatcher but I'm pretty sure I'm right about this.

[This message has been edited by Kentucky Nimrod (edited 03-30-2002).]