Garand gas cylinder plug tightening torque?

[Linstrum]

Since 1979 I have been using a large blade-type screwdriver turned with a Crescent wrench to tighten and loosen the gas cylinder plugs on my M1 Garands. I finally took some time this morning to machine a badly-needed cross-type wrench to fit the gas cylinder plug, so if anyone has the Garand repair manual handy to look it up, all I need now is to know now how many pounds-feet torque the plugs need to be tightened up to, I sure don't want to have one blow out again! It was awful hard to find.

For what it's worth, the gas cylinder plug and gas cylinder-front sight lock on the barrel muzzle both use a 9/16" by 32 turns per inch pitch thread! :veryconfu


rl849

[chasw]

My advice is don't torque it down too tight. 10 or 15 ft lbs is enough, IMO. I use moly grease on the threads of my rifle, so they don't seize up from the heat. The moly is so slippery, I get the opposite effect, the lock screw tends to back out over time. I need to tightening it after every trip to the range. Just about any large screwdriver will do, also the M1 combination tool has a tip made esp for the slot style lock screw. - CW

[pincherpartner]

Hi Linstrum,

I have the Operational and Organizational Maintenance Manual and under Gas Cylinder Group it says, " Inspect gas cylinder lock screw. Make sure it is tight, but not frozen or cross-threaded in gas cylinder."

Also, just for your reference, the general manual for the M1 FM-25 is online here -
http://www.ibiblio.org/hyperwar/USA/ref/FM/PDFs/FM23-5.pdf page 8 has the assembly instructions as well.

One thing, I've been doing is using an M1 Gas Cylinder Wrench. This holds the gas cylinder lock so that nothing gets tweaked when tightening or loosening the nut. The danger is that if the nut is tightened too much without supporting the lock then the cylinder and especially the front sight may get loosened up with how they mate with the splines causing some shifting of the sights while firing.

Fulton Armory has these wrenches for pretty cheap, compared to the other sources. But you could easily make one as well. While it is called a wrench, we don't use it to turn anything, just to stabilize that junction while we tighten and loosen the lock screw.

Best of luck,
Ron - pp

[Linstrum]

Hi guys, thanks for the information and suggestions. It really wasn't a lot of trouble to chop out a wrench tip like that on my milling machine, so I just went ahead and made a tool that fits like a big four-flute Torx driver that I can turn with a 9/16" hex socket on a regular mechanic's torque wrench.

Yeah, I think 10 to 15 pounds-feet torque at most sounds about right because the 9/16" by 32 turns per inch pitch threads are pretty shallow and the plug doesn't have all that much thread engagement. Its not like the "Jesus nut" that holds the main rotor assembly on some helicopters and supports the entire weight of the chopper in flight.


rl850

[nicholst55]

Hi guys, thanks for the information and suggestions. It really wasn't a lot of trouble to chop out a wrench tip like that on my milling machine, so I just went ahead and made a tool that fits like a big four-flute Torx driver that I can turn with a 9/16" hex socket on a regular mechanic's torque wrench.

Yeah, I think 10 to 15 pounds-feet torque at most sounds about right because the 9/16" by 32 turns per inch pitch threads are pretty shallow and the plug doesn't have all that much thread engagement. Its not like the "Jesus nut" that holds the main rotor assembly on some helicopters and supports the entire weight of the chopper in flight.


rl850

I just bought a square-shank #4 Phillips screwdriver; fits perfectly and works great.

[Linstrum]

Hi, nicholst55, if works okay there isn't anything at all wrong in using a #4 Phillips screwdriver to turn the gas plug. The K.I.S.S Principle is pretty good for most things, so if it works okay, go for it!

When I got my first Garand I thought the gas cylinder plug was meant to take a big Phillips screwdriver, but when I tried using a #4 Phillips to loosen the gas plug in my particular rifle all it did was start to dig out and bugger things up because the gas cylinder plug threads were tight from the plug probably not being removed and cleaned for decades. When I couldn't get it to turn without buggering up the drive socket, I switched to a large blade-type screwdriver that fit all the way down to the bottom of the socket and turned it with a Crescent wrench on the blade part of the screwdriver. Because I had a gas cylinder plug work loose and blow out once, I decided to make a tool that I can use a torque wrench on to make sure I get the plug tight enough, but not so tight as to damage the threads.


rl851