For posterity's sake, does anyone know the size of vent hole that Hook Boutin used to drill the gas plug?

Schuster makes / made ? a 1/64 drilled gas plug... however, it is "bored out 58%, for a larger expansion chamber "
M1A Vented and Bored Gas Plug

And .... while this has zero documentation ,
M1A Gas plug Question

Tony, I may have some gas plugs he drilled? Is there a means to ascertain exactly the size? I assume trying drill bits and find one that fits. The ones he used were tiny and he had a box full of them. They often broke due to the plug hardness. He stated it was to remove any potential vacuum present affecting free motion of the piston.

What gets reamed on a M25 gas mod?

hammonje said:

Found one on my NM SAI M1A. A 1/16" drill bit is not even close, too big. I would guess it is 1/32" or 1/64", but 1/16" is the smallest drill bit I have on hand.

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That looks significantly larger than the schuster 1/64th..

forceman said:

What gets reamed on a M25 gas mod?

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Forceman, I know nothing about the M25 gas mod. But not to long ago I was out in my hot garage working on my M14BR's piston tail and Jon Wolfe called me as he has a receiver of mine to rebarrel...
I mentioned I was working on the dwell and he advised me, as a novice, to just play with the piston tail as anything else requires reaming your gas plug to keep the volume of gas needed to cycle the action in a smooth manner... Assuming he meant shortening the gas plug to set back the gas piston to increase dwell? And this requires specialised equip.
I told him I just play with gas piston tails some; he said that is fine just make sure you have contact with the OP at rest and not the Bolt roller/OP Rod.

anthonypd said:

That looks significantly larger than the schuster 1/64th..

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The hole is obviously not very clean. Looks bigger than it actually is. Need a precise measurement. Rifle is 18755X serial number from 06/2006. Stock NM other than this mod. Shoots lights out. Mostly shot 100 yard reduced matches and clinics with this one.

bfoosh006 said:

Schuster makes / made ? a 1/64 drilled gas plug... however, it is "bored out 58%, for a larger expansion chamber "
M1A Vented and Bored Gas Plug

And .... while this has zero documentation ,
M1A Gas plug Question

Click to expand...

Due to family problems Schuster's is closed until July ('23)

Thanks Jason. I was just going to chase the hole with a drill bit and see if that was the right size.

Terry, for a clean hole on the M25 mod, I use a carbide #53 drill bit which is undersize from the 1/16 size, then I open it up to the proper size with a 1/16 carbide reamer

Tony.

tonyben said:

I seem to recall that he did that to all his builds. Does anyone know the size or does anyone have documentation for the rationale of the size range? Was it 1/64th?

I have the proper drill bits and reamers for the M25 gas cylinder mod, but I don't know the size for the gas plug.

I'll offer those mods to anyone who wants them.

Tony.

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Tony,

Hook used a #56 drill or .0465” diameter. Hope that answers your question! Have a great night!
Regards,
Steve 🙏🇺🇸🙏

Coming from you, that does help! Thanks so much! Did he, by any chance, overbore the plug as well, or was that just a Creedmoor sports thing, using the smaller hole listed on their site?

tonyben said:

Coming from you, that does help! Thanks so much! Did he, by any chance, overbore the plug as well, or was that just a Creedmoor sports thing, using the smaller hole listed on their site?

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No sir, he did not overbore. There was no further need for any further modification according to him. He drilled it on an old drill press from the AMTU. I’ll post a pic of it today.

Back in the 80's the National Guard Team tried vented gas plugs for about one season, before going back to solid plugs. It was found that the drilled plugs made no significant contribution to the accuracy of the M14NM rifle. I do have a couple of these original vented plugs if anyone wants to try one. We also tried slotted pistons with the same result. Slotted pistons may have some benefit when using heavier loads, but in those days we only shot M118 and M852.

In MHO...If it ain't broke, don't fix it.

Several years ago, I drilled my gas plug with 1/64 hole, which I believe is legal for Service Rifle competition. It's a very tiny hole! I didn't notice any difference in accuracy, functioning, or felt recoil. I increased the hole sizes several steps, but I got the best result from an oversized gas plug with increased internal capacity. Softer recoil and better accuracy.
I had no trouble drilling the plug with HSS drill bits.

tonyben said: "I have the proper drill bits and reamers for the M25 gas cylinder mod, but I don't know the size for the gas plug."
Tony, can you tell us about the M35 gas cylinder mod?

When Hook did mine, he just drilled the hole. He did not overbore the inside of the plug.

nsussf said:

No sir, he did not overbore. There was no further need for any further modification according to him. He drilled it on an old drill press from the AMTU. I’ll post a pic of it today.

Click to expand...

nsussf said:

No sir, he did not overbore. There was no further need for any further modification according to him. He drilled it on an old drill press from the AMTU. I’ll post a pic of it today.

Click to expand...