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Discussion Starter · #81 ·
Just my 2 cents...
Being a tinkerer playing around with what other guys have shown me about the M1A/M14 platform, i did become a fanboy for shims and unitizing the gas cylinder. Did not arrive there easily because i just could not wrap my head around changing something that appeared designed into it. However, the thought of the gas lock rattling on the barrel threads just never set right. I mean why bother having a barrel shoulder if not gonna use it?

Over the years, some of my M14s shot straight and true while others that looked and fit the same would string shots and/or make two groups about 3 inches apart which, to me, indicated something moving between shots. Yeah, for defense, 2 1/2 to 3 inch groups at 100 is awesome but i wanted more. Like, shooting old apples across the pasture at 300. The shims and unitized cylinder did help reduce the minute movement or changes in harmonics or whatever black cloud hoodoo happens before the rifle settles for the next shot.

Like someone brought up earlier in the conversation, if you over tighten the gas lock onto too much shim pack, weird things happen as the barrel heats up. The same thing happens with no shim and somebody cranks the lock tool hard to line up a 3-4 o'clock gas lock to insert the plug. Same thing.

The biggest advantage to the whole shim thing, imo, is the ability to increase the dwell time to it's max. Yeah, another rabbit hole conversation BUT, my experience on my own rifles running through thousands of rounds shows it makes a diffrence. Be it small or big depends on your perspective.

Shoot straight and enjoy the journey!
Smoky
Thank you sir!! Great advice
 

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I totally agree, unfortunately I live in New Jersey, and I struggle to find people I trust with the platform, the nearest people i have found are all in Pennsylvania or upstate New York. Trying to find people I can meet around my work schedule is verydifficult. I only have the Springfield documents that don't go in depth with accuriazantion of the rifle. Only basic care/maintenance and a document about slam fires.
Toney Ben you tube I think he’s on full 30 too... these guys are Dicks... ha welcome to the m14forum
 

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I don't believe you will find any reference to shims or buffers in training manuals on the M14 for a reason. I think you may find that some of these ideas have been perpetrated by some trying to establish something that never existed for a reason.
If anyone is keeping tabs I have de-shimmed. #teamnoshims


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The biggest advantage to the whole shim thing, imo, is the ability to increase the dwell time to it's max. Yeah, another rabbit hole conversation BUT, my experience on my own rifles running through thousands of rounds shows it makes a diffrence. Be it small or big depends on your perspective.
It is impossible for shims to change the dwell time, period.

The dwell time is fixed by the location of the gas passage in the cylinder relative to the gas port in the piston, and the size of the two holes. (Excluding ammunition variations, of course.)

You can move the gas cylinder forward, but that will not change anything as the port in the piston is still aligned with the passage in the cylinder by the gas cylinder plug, and it will take the exact same length of time for the two to become misaligned and cut off the gas.

Slope Rectangle Font Parallel Diagram


Oh, but it moves the operating rod forward so the roller takes longer to hit the cam.


Yes, but only by a MAXIMUM of 0.0175 inch before you start occluding the gas port in the barrel, which is less than the slop in the entire system. If you add up all the tolerances that locate where the cam in the operating rod sits in relation to the breech face, and the tolerance in the location of the roller to the breech face, between least material conditions and maximum material conditions, you get an acceptable variation of about 0.025 inch

Incidentally, the hole in the gas cylinder is smaller than the hole in the piston by about 0.040 inch.

Barrel gas port - 0.076
Cylinder gas passage - 0.111
Gas cutoff valve passage - 0.118
Piston gas port - 0.147

The most reliable way to reduce the dwell time would be to reduce the diameter of the gas port in the piston, assuming we don't do major surgury like adding weight to the operating rod, or repositioning the gas port in the barrel.
 

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10 years ago, we'd have been on the same side of the discussion. All your points are the very ones I supported. Given results of my groups experiments at the time, I was converted. To this day, I cannot say exactly what causes the change but the brass changes its throw from 1 to 2 o'clock or 3 to 4 o'clock. An observable diffrence. The groups on most and I am saying most, not all, have tighter groups. At the end of the range day, a removable tweak that improves performance became something I can recommend to others as long as gas cylinder is not placed so far forward as to crash the bolt roller. The safe place I see for that is to be sure the gas plug has 5/8 to 3/4 turn left to screw in after touching the op rod. Hope that all makes sense. I could show you way better than tell you.
 

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Roger that Sarge, you want some elbow grease and headlight fluid for the humvee as well?
[/QUOTE]
Can’t help you much with the gas plug o-ring but I found this in my motor pool shop bay once. Some good info in this forum too.
Handwriting Rectangle Textile Wood Office supplies

( I don’t mean to hijack a thread, found this can and took the photo 3 years ago and been looking for a chance to use it ever since)
 

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It is impossible for shims to change the dwell time, period.

The dwell time is fixed by the location of the gas passage in the cylinder relative to the gas port in the piston, and the size of the two holes. (Excluding ammunition variations, of course.)

You can move the gas cylinder forward, but that will not change anything as the port in the piston is still aligned with the passage in the cylinder by the gas cylinder plug, and it will take the exact same length of time for the two to become misaligned and cut off the gas.

View attachment 469129

Oh, but it moves the operating rod forward so the roller takes longer to hit the cam.

Yes, but only by a MAXIMUM of 0.0175 inch before you start occluding the gas port in the barrel, which is less than the slop in the entire system. If you add up all the tolerances that locate where the cam in the operating rod sits in relation to the breech face, and the tolerance in the location of the roller to the breech face, between least material conditions and maximum material conditions, you get an acceptable variation of about 0.025 inch

Incidentally, the hole in the gas cylinder is smaller than the hole in the piston by about 0.040 inch.

Barrel gas port - 0.076
Cylinder gas passage - 0.111
Gas cutoff valve passage - 0.118
Piston gas port - 0.147

The most reliable way to reduce the dwell time would be to reduce the diameter of the gas port in the piston, assuming we don't do major surgury like adding weight to the operating rod, or repositioning the gas port in the barrel.
Hhhmmm, I think you overlooked shorting the tail of the gas piston for increased dwell.

The passage in the offside of the spindle can also be made smaller/reduced.

Pic #1. Std spindle.

Office supplies Finger Nail Gadget Communication Device


Pic #2. Offside of spindle spotted for new passage.

Finger Cosmetics Office supplies Thumb Material property
 

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Hhhmmm, I think you overlooked shorting the tail of the gas piston for increased dwell.

The passage in the offside of the spindle can also be made smaller/reduced.

Pic #1. Std spindle.

View attachment 469400

Pic #2. Offside of spindle spotted for new passage.

View attachment 469401
What diameter are you going for?

As for shortening the tail of the piston, I don't think you have much room to play with before you start to get roller contact with the end of the cam.
 

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Discussion Starter · #91 ·
Roger that Sarge, you want some elbow grease and headlight fluid for the humvee as well?
Can’t help you much with the gas plug o-ring but I found this in my motor pool shop bay once. Some good info in this forum too. View attachment 469398
( I don’t mean to hijack a thread, found this can and took the photo 3 years ago and been looking for a chance to use it ever since)
[/QUOTE]
Finally!!!!! Autozone, Advanced, Pep Boys, O Rielleys, they all laughed!! Knew it had to be there somewhere 🤣🤣🤣🤣
 

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I believe the o ring is the same size as a muffler bearing o ring. But it has to be for 1996 and older the new muffler bearings are sealed. Don’t use that gun without that oring, it will sound like a pinto when you pull the trigger. I prefer the Pep boys brand o rings. Any thoughts on what brand muffler o ring you perfer. Rember the part of the gun with a hole in the end you point away from yourself.
 

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Can’t help you much with the gas plug o-ring but I found this in my motor pool shop bay once. Some good info in this forum too. View attachment 469398
( I don’t mean to hijack a thread, found this can and took the photo 3 years ago and been looking for a chance to use it ever since)
Finally!!!!! Autozone, Advanced, Pep Boys, O Rielleys, they all laughed!! Knew it had to be there somewhere 🤣🤣🤣🤣
[/QUOTE]
Lmao that was priceless, I may know of a young private who was sent for a bucket of steam from the motorpool steam nozzle. Lol
 

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Hey! Make sure you keep the lid on that bucket, I don't want to have to you to get a second.
Yes sir. I just am having a hard time finding the fill nozzle. I’m 46 now to be young and innocent, It’s like the left handed monkey wrench.

i don’t get with you tube and all the information how someone can take apart there weapon and not be sure if they lost parts. I didn’t have you tube or Google, I had manuals that were like reading sandscrit, or you asked someone to teach you. Chris very nice to meet you.
 

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Discussion Starter · #99 ·
Yes sir. I just am having a hard time finding the fill nozzle. I’m 46 now to be young and innocent, It’s like the left handed monkey wrench.

i don’t get with you tube and all the information how someone can take apart there weapon and not be sure if they lost parts. I didn’t have you tube or Google, I had manuals that were like reading sandscrit, or you asked someone to teach you. Chris very nice to meet you.
Because YouTube, and Google suppresses anything firearm related if they can. And I didn't buy an AR like everyone else. Got conflicting information, and wasn't sure. Thought I'd ask a question. Thanks for the help fudd
 

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Because YouTube, and Google suppresses anything firearm related if they can. And I didn't buy an AR like everyone else. Got conflicting information, and wasn't sure. Thought I'd ask a question. Thanks for the help fudd
People are just giving you a hard time in good fun. And if you noticed this forum is for m14’s. I personally have 3 one being in 30-06 with matching numbers. We all get joked with here.
 
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