Looking to buy a Garand, what do I need to know?

[bpitcher]

Great rifles.

If you're close enough, the CMP stores will allow you to hand pick your rifle from the racks available. I'm not sure what inventory looks like these days, but they used to advise calling ahead to check.

 

[2531usmc]

The CMP advises to not use .30/06 ammunition in M1 Garands, 1903s, and 1903A3s that is loaded beyond 50,000 CUP and has a bullet weight more than 172-174gr.

I understand the part about not buying ammo over 172 gr. But how do you know if the ammo you are purchasing is less than 50,000 CUP?

 

[RockAndSage]

GCA article exerpts on Garands and ammo.

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I think I owe you an apology, friend. Your images here from the article caused me to go down something of a rabbit hole, where I also found this post/article - which appears pretty exhaustive on actual testing of the subject.

From what you posted, and this article I'm sharing, it seems this issue of non "Garand safe" ammo causing bent op-rods is yet again another piece of Fuddlore. As you said. It is absolutely astounding how powerful that crap becomes engrained and endemic in the shooting culture. And once "everybody knows", it's just God's truth until beaten to death with excessive volumes of science and public ridicule.

Here's the link: https://www.m14forum.com/threads/commercial-ammo-in-the-garand-test-results.542477/

Short version: they pretty much tested/shot all the ammo they could find, and found zero problems with the op-rod. It might still be advisable to get that plug, avoid heavier bullets, etc, but as far as I'm concerned, at this point, the science says it's a non-issue. Thanks for sharing what you did.

 

[RockAndSage]

I understand the part about not buying ammo over 172 gr. But how do you know if the ammo you are purchasing is less than 50,000 CUP?

OP, this is the load data for dozens and dozens of loads the engineers fired out of Garands in the testing article I posted a link to above, including chamber pressures. It's extremely interesting:

 

[Rotnguns]

I think I owe you an apology, friend. Your images here from the article caused me to go down something of a rabbit hole, where I also found this post/article - which appears pretty exhaustive on actual testing of the subject.

From what you posted, and this article I'm sharing, it seems this issue of non "Garand safe" ammo causing bent op-rods is yet again another piece of Fuddlore. As you said. It is absolutely astounding how powerful that crap becomes engrained and endemic in the shooting culture. And once "everybody knows", it's just God's truth until beaten to death with excessive volumes of science and public ridicule.

Here's the link: https://www.m14forum.com/threads/commercial-ammo-in-the-garand-test-results.542477/

Short version: they pretty much tested/shot all the ammo they could find, and found zero problems with the op-rod. It might still be advisable to get that plug, avoid heavier bullets, etc, but as far as I'm concerned, at this point, the science says it's a non-issue. Thanks for sharing what you did.

Excellent and informative post. The Schuster plug was developed not to protect the op rod, but for the service marksmanship teams to tune the gas vent so that the Garands would function with loads using heavier bullets for longer distances. There is also a plug made for the M1A.

 

[Rotnguns]

OP, this is the load data for dozens and dozens of loads the engineers fired out of Garands in the testing article I posted a link to above, including chamber pressures. It's extremely interesting:

Very interesting! I found this great website that gives a wonderful and detailed explanation of the operation of the M1 Garand, with pictures and graphs; https://m1-garand-rifle.com/gas-pressure.html#google_vignette

But I'm a bit confused, because the source I linked shows pressure peaks an order of magnitude lower than the data source that you linked. Going to investigate further...

Edit: Found an interesting thread on the M14 that claims gas pressure in the cylinder is much reduced from the gas pressure at the port of the barrel due to flow through the port restriction. Using the information provided in the M1 Garand vignette link, with a piston diameter of about 0.526 inches, with a pressure peak of about 1100 psi acting on the piston face, the piston experiences an impulsive force of about 240 pounds. Trivial, given the cross-sectional area of that op rod. And to note - the force peaks over only about half a millisecond; the inertia of the op rod, piston, and bolt are sufficient to keep the whole assembly from moving until the bullet clears the barrel; once the recoil system begins to accelerate, the impulsive force is considerably reduced. It's highly questionable whether the stress field can be fully developed in the op rod under such a brief impulsive load; rendering claims of op-rod damage due to buckling very questionable.

https://www.m14forum.com/threads/m1-garand-port-pressure.477480/