How does one know if an M305 gas system needs to be shimmed?

S

sgt.rock

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I have a 305 inbound and don't know diddly about them. I read the sticky's about M14's but it doesn't touch on gas system analysis and shimming as needed. I live in a kind of remote place, so I end up doing a lot more work on my own guns than the average joe.
So, does anyone have a pictoral of what to look for? How does one know if the gas system is indexed correctly. And is there a way to fix it at home if there is an issue? Thanks everyone. I love tinkering with guns, but DO NOT do things that are over my head or above my skill level. I have no issue shipping this to a gunsmith or the M14 medic to do work if necessary......BUT , I would love to learn to do these things myself. If anyone has a "pictoral" of a step by step process in what to look for and how to fix an issue I would be eternally grateful. Thanks guys.
 
YouTube will show you how I'm sure...try looking there for a video "how to". Here's one: https://m.youtube.com/watch?v=uCyYx0GpixM
It's easy to tell if shimming is needed. Just remove the gas plug, then, with the action locked back and the gas piston extended out towards the receiver, check to see if the gas lock (figure 8 shaped piece behind the gas plug) is loose. It should tighten up at about the 5:00 position. If you need to shim your gas system, you'll need some proper tools to remove the flash hider. The video should cover all you need to know.
 
Look in dealer networks...under tactical training there's tactical teacher, Barney has posted all kinds of really good information there.
He has a thread going there that shows you how to do all kinds of stuff.
 
shawn said:
If yer #### falls off shim it

Shawn
Click to expand...

Okay here's how to tell if you need shims:

* Loosen then remove gas plug. Place on bench so it don't roll off and dent the fine threads on cement shop floor
* tighten up gas lock, tighter , then tightest PAST the original, bottom dead center, 6 o'clock position
* HOW much Further does it rotate? THAT is the slop that we have to / need to take out by ensuring super tight position at bottom dead center

Does it turn PAST the bottom dead center? How far past bottom dead center? Just FYI, USGI M14 rifles used to tighten up at 12 noon and sometimes 1300 (no joking). That's how sloppy USGI M14 rifles were ALWAYS. Norinco rifles tend to be tighter. :eek:



I have to trial and error to see if it's tight / contact at around 4 or 5 o'clock and rubber mallet to 6 (bottom dead center)

You guys gotta come to a clinic before yer #### falls off! ha ha ha ha :nest:

Barney
 
I'll say it...

You don't have to shim the gas lock to have the rifle operate well, but it is usually done to improve accuracy. If you want to just shoot stuff in the bush or a gravel pit you won't need to worry about it.

Going for one MOA will require this and a few more tweaks. Good luck and enjoy the tinkering.
 
I thought shimming was to center the gas port in the barrel to the line up with the one in the gas cylinder. here's a link to the way to do it.
ht tp://m14forum.com/reference/89156-shimming-gas-cylinder-gas-port-alignment-how.html
 
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