Project: Silenced M1 Garand

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  • laf

    Marksman
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    11   0   0
    Aug 21, 2011
    222
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    Lafayette
    I've got a goal of putting together a silenced M1 Garand in .308. I'm in search of some help for obstacles I may encounter and a gunsmith interested in threading a barrel and headspacing it. The goal is to have a functioning M1 in .308 that accepts a YHM QD mount on the muzzle and cycles .308 rounds. I've purchased the rifle already and it runs fine on .30-06 so I'm happy with the action and internals. I've written in to the Silencer Co podcast and they answered my question, but weren't helpful in the assembly of the rifle. It was already done when they got it and didn't offer much on the way of how they put the SilencerCo qd mount on it. https://www.stitcher.com/podcast/bea...rms/e/59727842 14 minutes in for my question.

    I've bought; Korea era M1 with new CMP wood, Criterion .308 24" barrel that needs finished reamed and headspaced on the rifle. A gas cylinder lock that needs cut a bit. An adjustable gas screw from Schuster MFG. And a QD mount in 5/8-24 for YHM silencers.

    An issue I found already is the barrel isn't thick enough to support 5/8-24 threads. The gas cylinder lock slides over the muzzle and into the gas system, if I remember right the barrel is .516" in diameter. I think it will support 1/2-28 threading or 1/2-36 threading and YHM sells .30 cal QD muzzle brakes with both of those pitches. https://yhm.net/thread-specifications has drawings of threading that they require for the QD mounts. I've also found that that gas cylinder lock is too long to allow enough threads to be cut into the barrel. I have an extra that I purchased that I think can be cut to allow enough length for threading. In the picture below the muzzle on the left has a small shelf under it from the gas lock screw. I don't think that gas lock screw 'lip' actually contacts the barrel and needs to be present. If the lock screw can be cut then the barrel will have enough exposed to allow it to be threaded. I measured from the crown to the end of the gas lock screw and it was .670" long. From the muzzle to the lip of the screw was closer to 0.3" and much too short to allow it to have enough threads for a mount to be seated.
    rimg.php


    So, are there any suggestions on where to go to have a barrel that's off the rifle threaded? Then it'll need headspaced and finish reamed to .308. There's very little documentation about the few rifles that others have done but apparently it can be done and I'd like to do it.
     

    JeepHammer

    SHOOTER
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    0   0   0
    Aug 2, 2018
    1,904
    83
    SW Indiana
    I'm pretty happy with my OSS suppressor.
    I switch it between my SR25, M1A & bolt rifles.

    There was a suppressed M1 at the machine gun shoot this spring, but I didn't take a good look at it, don't know what they used or how they did it.
     

    laf

    Marksman
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    11   0   0
    Aug 21, 2011
    222
    28
    Lafayette
    Thanks for the replies! I'll give ZR Tactical a call and see if this a project they're interested in pursing with me.

    I've been interested in the OSS equipment, but I've already got a .30 cal Phantom TI from YHM that I'll be using for this project. Seems to be a few of the suppressed Garands out there, just mysterious on what they did to get it running.
     

    JeepHammer

    SHOOTER
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    0   0   0
    Aug 2, 2018
    1,904
    83
    SW Indiana
    I picked OSS because NO FACE BLASTING on the SR25, doesn't screw with the gas system at all.
    Guys shooting full auto don't see the cyclic rate increase, no gas in the face, and I don't have to adjust gas or rounds on my semi-autos.
    It also takes full power rounds without eating itself and it cleans easy.

    It doesn't screw with zero much either.
     

    Disposable Heart

    Grandmaster
    Rating - 99.6%
    246   1   1
    Apr 18, 2008
    5,805
    99
    Greenfield, IN
    You're going to DEFINITELY need an adjustable gas block and will be spending alot of time attaching and detaching the can to get it tuned, but once you do... it will be an awesome project!
     

    laf

    Marksman
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    11   0   0
    Aug 21, 2011
    222
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    Lafayette
    I've called around to a few places and nobody wants to touch this start to finish. Can't say I blame them since it's not common, but who wouldn't want to say they built one? So I'm going to one place to have the barrel threaded. I'll chop off the gas cylinder lock lip area that extends out over the barrel myself. I do have a Schuster adjustable gas plug on order and will be using that for sure. I have it on my Garand that I use for plinking and the plug does what it says it does very well. I ordered a new QD brake from YHM in 1/2x28 for the 30 cal cans so nobody accidentally puts a 5.56 can on it. I had thought about using a repurposed 5.56 flash hider QD mount drilled out but "safety third" and all. Another place will have to headspace and finish ream the barrel once it's threaded. Right now there's nothing to show off but as it gets assembled I'll post pictures.
     

    AlVine

    Marksman
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    0   0   0
    Feb 12, 2014
    152
    28
    Owen Co.
    This sounds very cool. I’d think on a Garand with a Schuster plug it would be easy to open the plug so the action doesn’t cycle, for really quiet subsonic loads.
     

    laf

    Marksman
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    Aug 21, 2011
    222
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    Lafayette
    I've collected most of the parts necessary to start this project now. I've got the barrel in from Criterion in .308 Win. I've got a 1/2-28 brake from YHM. Interesting note about that brake is it's the same length as my .223 flash hider. I thought the .30 cal stuff was supposed to be longer to prevent you from threading a .223 can on it and ending up with a problem. But it's got a .30 cal hole so it'll be safe to shoot for me. The Schuster adjustable gas plug so I can dial the gas way down. I got a new old stock gas cylinder lock that I cut the lip off of using a hacksaw.

    Threading the gas lock on the barrel and gas plug comes close to the thread minimums for rifle specs. I'm not sure if it will actually make it or not. My calipers say there's .613 inches and YHM wants .620 plus another .060 for shoulder. I know I don't have that space. Not sure what to do about that, cut the shoulder space and thread what's left and call it good? The specs for pistols are much shorter, .400 plus .060 for the shoulder but a lot less pressure too.

    IMG_6439.jpg
     

    laf

    Marksman
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    Aug 21, 2011
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    Lafayette
    Good news bad news. Bad news; I can't math. Good news; local machine shop looked at it, said they'd do it and there *is* enough meat on there for 1/2-28 centerfire threading with the gas cylinder lock screw. So I'll have another update in 2-3 weeks when this fits into their schedule. I was afraid I'd need to go M15-1 threading or something and buy another QD mount but turns out I'm just not good enough with calipers to know what I'm working with.
     

    laf

    Marksman
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    Aug 21, 2011
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    Lafayette
    I've seen the ones that replace the gas lock, but they're meant for attaching muzzle brakes or similar. I'd be scared they aren't concentric and that my can gets an extra large exit hole by accident. It's been a short 3 days so I'll just sit tight while my barrel gets threaded.
     

    laf

    Marksman
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    Aug 21, 2011
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    Lafayette
    Been a few weeks and had to follow up with the shop to see if it was done. I got the barrel threaded 1/2x28 and it has enough room for the gas lock and the muzzle brake! Needs to be installed on the receiver now.
    IMG_6698.jpg
     

    laf

    Marksman
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    Aug 21, 2011
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    Lafayette
    Another update. Took the Garand and barrel to Jerry Johnson and had him put it on and finish ream the chamber to .308 Win. Took about an hour and the local gun store was worth the drive while he did the work. The gas cylinder lock screw mounts up tight and the gas plug fits as well. However the gas plug isn't flush with the gas lock screw and stands proud. So the shims will need to be cut flat along the bottom to not interfere with that and still mount up tight to the barrel.
    58362133642__7A9881CF-2C65-459A-A07A-A85378AC374B.JPG
    This picture shows the gap between the QD mount and the barrel caused by the gas plug. It is an adjustable gas plug.

    IMG_6800.jpg
    Here's the Garand wearing the mount but not ready to fire quite yet. I need to cut the shims down to size to get it timed right.

    IMG_6803.jpg
    And the piece de resistance. My Garand wearing the YHM Phantom Ti! The shims should get cut down by Wednesday so I hope to have some time to burn on the 4th and really test it out. Otherwise it'll have to be next weekend.
     

    laf

    Marksman
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    Aug 21, 2011
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    Lafayette
    The Garand made it's way to Winamac today for a test run. Used a SLED and put a few single shots down while adjusting the gas from wide open to more closed to get it to lock back after each shot when just the brake was on. Checked the targets and no signs of anything wobbling coming out so I put the YHM Phantom on and sent a few 150 grains down and wow, what a great project. It is way overgassed with the can and I tried backing the gas system down but I think this might be a load development issue as well. I do plan on using this to harvest a deer so I'll get to work with some nicer rounds and the H4895 powder I have stocked up and see what I can get working in there.

    Girlfriend took some video of the first shots and tossed a few still shots in there.

    [video=youtube;BZigiLimkps]https://www.youtube.com/watch?v=BZigiLimkps[/video]
     

    laf

    Marksman
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    Aug 21, 2011
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    Lafayette
    Yeah! The brake did catch her off guard. It's not unreasonably loud, but the .308 with a brake feels louder than a standard .30-06 Garand. Not shown is my 12" .308 AR-10 pistol out at the same trip with a brake and that is way worse than the Garand.

    After consulting with some colleagues I'll be dialing the gas system almost all the way down so it only reliably functions with the can on there. I built it for the can, I'll use it with the can exclusively. They watched the video and with the brass landing and symptoms I experienced they believe it's operating way too fast with the can on.
     
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