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  1. #1

    Default Post-War M1 Alpine Carbine (Inherited) Feed Problem

    First let me say that I know all about the lack of quality and collectability of these cloned carbines, then let me say that I inherited it from my late father-in-law who bought it at a pawn shop back in the '60s. Then, I have to say that I'm a bolt-action guy & know little or nothing about semi-automatics and how gas systems are supposed to fit together. Now for my question:

    I took this rifle to the range to shoot it for the first time on Saturday. It had immediate feed problems, so I fired a couple more rounds by hand-feeding it, then packed it up.

    My first thought was the gas system, so this morning I broke it down to look at the piston and cylinder. The first thing I noticed was that the piston nut was loose and the piston sorta flopped around in the cylinder and even had noticeable side-to-side movement. This can't be normal....do I replace the piston? How snugly should it fit? Thanks, Butch

  2. #2
    Join Date
    Dec 1969
    Posts
    2,122

    Default

    I'd recommend buying a new USGI gas piston and a nut.

    CAREFULLY remove the nut using a GI-type piston nut wrench.
    Clean out the gas cylinder. A good way to do that is pack some paper towel in and liberally soak the towel with some well-shaken Slip 2000 Carbon Cutter.
    You might use an automotive carbon remover, but be careful of the finish.

    After a 15 minute soak pull the towel and check the cylinder for carbon.
    If there's still some present, soak again.

    Once the carbon is gone, dry the cylinder and this ONE TIME ONLY, apply a thin coat of lubricant, then wipe it as dry as you can with patches or paper towel.
    The gas system MUST be run dry of lubricant or solvent.

    When cleaning the carbine after firing, lay the sights on the bench and clean the bore with the rifle upside down. This will prevent solvent or lube from running into the gas system.
    Anything that gets into the system will instantly carbonize into a sticky sludge that will cause stoppages.

    Next, use a drill bit TURNED BY HAND to check the gas port into the barrel to insure it's clean and free of fouling or old lubricant. Don't damage the port with the drill bit. Just use it to be sure the port is clear.
    Usually, there's a hole on the bottom of the gas cylinder that will allow inserting the drill bit.
    You can also use copper wire, but be careful not to get it stuck.

    Install the new piston into the gas cylinder and start the new nut by hand to protect the threads.
    Use the piston nut wrench to tighten the nut down tight.

    Get a center punch and round off the tip slightly.
    Use the punch to stake the nut in place. Do this by using the dulled punch to move some metal from the edge of the gas cylinder so it moves between the "lugs" of the nut and prevents it from unscrewing.

    Some people recommend using a non-Permanent Loctite. This will usually not hold since the heat of the gas will soften and degrade the Loctite.

    You can usually buy new USGI gas pistons and nuts and the wrench from these sources:

    http://www.m1garandrifle.com/

    http://www.fulton-armory.com/

    http://www.billricca.com/

    Here's a site that has all the USGI Ordnance manuals on the carbine.
    These show how to service the gas system and replace and stake the nut.

    NOTE the information near the top of the page on what user name and password to use:

    http://www.biggerhammer.net/manuals/

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