strength of a garand?

[mbpautz762]

I was just reading in another thread about how the garand has one of the strongest actions out there, but using some types of commercial ammo can damage the operating rod. does this mean that with an adjustable gas port like a schuster you can run ANY commercial 30.06, assuming it's adjusted properly? do you think there's any danger of the chamber not being able to handle the heavier loads, or is the only problem with the operating rod? thanks everyone - just trying to make up my mind between an M1a and a m1 garand, and I know there aren't any ammo issues with an m1a.

 

[Art Eatman]

I've never heard of anything beyond the op-rod deal...

 

[Jim Watson]

How much heavier a load do you need?

Anyhow, if you go back to 1947 after there had been four million Garands made and used in war, Hatcher says: "In trying to determine the ultimate strength of his 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 lbs per square inch. (Would be read out as CUP now.)
At this latter figure, cracked left lugs on the bolt began to be seen. A gun in which the bolt had the left lug cracked was then fired an endurance test of 5000 rounds of service ammunition, using the cracked bolt, which showed no further deterioration. The US M1 rifle thus has perhaps the strongest action of any military shoulder rifle in existence at this time."

 

[dmazur]

Just because it's an adjustable orifice doesn't mean it can handle any commercial load. I would be especially leery of the "light magnums", which are trying to wring the last bit of performance out of that case capacity with special powders.

It may be possible to develop more gas pressure than the adjustable device can bleed...I don't have any experience with trying to see how far I can push it.

The ultimate resource should be the gas lock screw manufacturers, McCann and Schuster (two different styles of a similar thing.) Ask them what the limits are, if any, and specifically mention light magnums.

Personally, I wouldn't be happy with a load that provided full action cycling with the largest orifice setting. The largest orifice is supposed to disable the action. You adjust smaller until it just cycles reliably.

 

[blitzen]

If It's a currently manufactured gun, (M1a or M1) I would ask the manufacturer. I have a late modle M1a and I did in fact shake the op rod apart after shooting some Remington 180 grain factory loads. I don't know if it was because of the load itself or if something was out of kilter from the git go. I sent it back and they (Springfield) fixed it up. I now stick to a max bullet weight of 168 grains. I think the book says you should stick to a bit less. Sorry to get off the M1 thing but you did through in the M1a. I would say that there might be ammo issues with the M1a but others will clear that up.

 

[mbpautz762]

sorry - I should've been more clear: I wasn't meaning I wanted to shoot the heaviest stuff I could find. what I really meant was that I wanted to shoot longer hunting bullets, like 180 - 200 gr loads, and I just assumed the heavier bullet would develop a higher pressure. but according to those figuers, I'm sure it wouldn't make any difference!

 

[dmazur]

Here's a link to reloading for the M1A/M14, which discusses powder selection and other things. It mentions damaging the op-rod.

http://www.zediker.com/downloads/m14.html

The op-rod in a M1A is shorter, so you don't hear about this as much as with a Garand. However, the design is very similar.

With any gas-operated rifle, there are generally concerns about ammo type. I remember a Remington 742 caution against "light magnums" specifically, for example.

At any rate, Schuster also makes an adjustable gas plug for the M1A...

If you check a reloading manual, I believe you'll find loads that develop very similar chamber pressures for a wide range of bullet weights. Pressure is a function of both the amount of powder and the bullet weight. Generally, as the bullet gets heavier, the amount of powder allowed gets lighter, for the same pressure.