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Discussion Starter #1
Hey fellas,

Can someone please tell me the overall length of the M14 gas plug and the depth to which it is drilled? I want to get an idea of how much volume there is inside. Also, can someone give me the diameter of the shoulder on the plug that sits inside the gas lock?

This is for a whacky Garand tanker build... Basically a poor man's Mini-G. I'm omitting the gas lock, but I need a high volume plug, so I want to see if I can cut an M14 plug short and thread that shoulder that sits in the gas lock 9/16-32 to match the Garand's gas cylinder threads.

Thanks!
 

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Ovl = 1.660 - .015
Hole = .318 dia +.008 x 1.320 +.015, plus a 118 degree point
Thread = .545-40 UNS-3A, the bearing diameter is .545 -.003

I think an M14 gas plug is too small....the dimensions of a 9/16-32 are:

Major dia - .5625 -.006
Pitch dia - .5467 -.0026
Minor dia - .5253 Max

You can just make your own plug.
 

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Discussion Starter #3
Ovl = 1.660 - .015
Hole = .318 dia +.008 x 1.320 +.015, plus a 118 degree point
Thread = .545-40 UNS-3A, the bearing diameter is .545 -.003

I think an M14 gas plug is too small....the dimensions of a 9/16-32 are:

Major dia - .5625 -.006
Pitch dia - .5467 -.0026
Minor dia - .5253 Max

You can just make your own plug.
Wow, thank you for the outstanding detail! That's a bummer... I was really hoping the bearing was just a little larger. The thread on my Garand plug is .556 but the bearing is .562. Looks like it's 2 thousands smaller than the pitch diameter of the thread. The internal threads on the cylinder I have are .532 (I don't have my micrometer on hand, so just going off a caliper measurement right now). The best I could do is 6.5 thousands of radius interference. Seems reeeal skimpy considering that the thread specs call for at least 9.75... Part of me wants to try it just to see what happens, but the rest of me wants to flick myself in the ear, lol.

I can definitely make a plug, but I'm trying to cut cost as much as possible. I'm a gunsmith and I'd like to offer these conversions for sale as a simplified alternative to Shuff's beautiful Mini-G. It's an awesome rifle and his parts are beautifully made, but it's just out of reach for a lot of guys... The other benefit is that no in-spec Garand parts are harmed in the process of making mine, so you can always convert back to M1, or sell off the unused barrel, op rod, and gas cylinder.

I'm thinking a cheaper and simpler option would be to use a BM59 plug and make or buy a cylindrical spacer with the same thickness as the gas lock to act as a shoulder to lock against. However, I expect it will have significantly less internal volume than the M14 plug. The other consideration is that I'm planning to leave the barrels at .625 OD so they can easily be threaded for a standard 5/8-24 muzzle device. A crush washer sits directly against the front of the gas cylinder. I can use a BM59 plug and still fit an A2-profile flash hider, but I need to take some more measurements to find the maximum diameter of brake that I could use. using an M14 plug, I'd probably be able to use anything that would make any sense.

Cheers,

Steve
 

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I wouldn't want to discourage anyone from pursuing their dreams, but this sound a lot like reinventing the wheel. The M14 gas plug works fine as is.
 
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