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This is a discussion on Forgotten Technology? within the Accuracy forums, part of the M14 M1A Forum category; It is often stated that the use of heavy bullets in the M14 is not recommended due to higher port pressures for the desired velocities, ...


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Old March 1st, 2017, 02:38 PM   #1
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Forgotten Technology?

It is often stated that the use of heavy bullets in the M14 is not recommended due to higher port pressures for the desired velocities, and the associated hammering of the system.

There have been a few 'solutions' to this, the slotted piston, or, my favorite, a smaller port in the piston, but, these still have limits to what they can accomplish.

I ran across the image below, while going through my files from Springfield Armory, it was their original solution to the problem:





A simple pressure relief valve that replaces the gas plug. It was dropped from the T44 design because it wasn't necessary and the Army could simple mandate the port pressure.

Anyone know the thread pitch on a gas plug?

EDIT: This may not be best suited for the "ACCURACY" category, if not, Mods, please move to the appropriate place. THX.

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Old March 1st, 2017, 03:21 PM   #2
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Interesting wonder what it looks like inside? It has a screw on the end for cleaning I rekon, still I wonder what in there.

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Old March 1st, 2017, 03:40 PM   #3
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Do you have any info about whether it was intended for improved accuracy, or as a 'safety device' to prevent damage if over-pressure situations occured.

Mechanically, it looks to me like more 'moving parts' that could be a cause for accuracy / function problems.

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Endwell NY USA

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Old March 1st, 2017, 04:33 PM   #4
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Grandfather of the Schusters we use today.

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Old March 1st, 2017, 04:38 PM   #5
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Quote:
Originally Posted by nf1e View Post
Grandfather of the Schusters we use today.
I was wondering if this was adjustable or not? Which do you use Art, the vented or adjustable. I'm asking this BC I would like to shoot hotter rounds while hunting. Sighting process and me playing plus actual shots under 30 per year.

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Old March 1st, 2017, 04:41 PM   #6
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Quote:
Originally Posted by Wasted ammo View Post
I was wondering if this was adjustable or not? Which do you use Art, the vented or adjustable. I'm asking this BC I would like to shoot hotter rounds while hunting. Sighting process and me playing plus actual shots under 30 per year.
I keep both in my workshop, but have settled on using the bored and vented. They seem to be less troublesome.

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Old March 1st, 2017, 04:45 PM   #7
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That's why I'm here I learn something unexpectedly everyday!

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Old March 1st, 2017, 06:58 PM   #8
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It is a fixed pressure relief valve, The pin end of the enlarged part (the valve) pokes into a hole in the front of the "gas plug" pressure pushed it into the spring. The weight of the spring keeps it closed until the pressure x area exceeds the spring pre-load. Then it lifts off it seat and allows gas to escape. The long rod on the cap is to prevent over-travel of the valve.

You could make it adjustable by shimming the spring (changing the pre-load), but, it is really only there to open if the port pressure is above what is safe to the system probably around 17,000 psi. The pressure relief valve only shows up on the very early expansion systems of the T44 and other T-series rifles that used the same gas system.

While I don't think it would be all that detrimental to accuracy, the further you move away from a simple sliding wedge single shot with a bull barrel, the more things can interfere with accuracy....

(I still think a smaller piston port is the best solution)


Last edited by lysander; March 1st, 2017 at 07:10 PM.
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Old March 1st, 2017, 07:07 PM   #9
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I would assume the threading was or would be the same as a std. gas plug? I like the idea of a smaller port just not in the piston, I like too drill the off side of the spindle.

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Old March 1st, 2017, 08:49 PM   #10
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Quote:
Originally Posted by Phil McGrath View Post
I would assume the threading was or would be the same as a std. gas plug? I like the idea of a smaller port just not in the piston, I like too drill the off side of the spindle.
Interesting modification. Interesting...

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Old March 2nd, 2017, 04:41 AM   #11
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drilled

lysander said:
Quote:
(I still think a smaller piston port is the best solution)
I am having satisfactory results with a drilled gas plug (1/16"), primarily to improve performance with 168 grain or lighter. I just need to get my vision sorted.

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Old March 2nd, 2017, 08:27 AM   #12
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Oh, this would be an excellent addition for those running suppressors, seeing the major problem with suppressors is increased port pressure.

Might be a market for these things if the HPA gets traction....

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Old March 2nd, 2017, 08:32 AM   #13
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schuster makes several m14 gas plugs and smith ent makes a fatty for suppressor use

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Old March 2nd, 2017, 09:05 AM   #14
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By the way, the threads for the gas plug are .545-40. It's an uncommon size, but I was able to get a set of tap and die from Widell for a lot of money.

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