M14 Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 ·
Is there a good way to check the position of the gas cylinder relative to the hole in the barrel? If I shine a flashlinght down the barrel, I cen see the light looking through the hole in the underside of the gas cylinder when the piston is removed. Does that mean it is aligned correctly?

I am curious, because my M1A wasn't feeding correctly recently. This is only the second time I have been to the range with it. I may not have cleaned the gas cylinder correctly after the first time, but I am also wondering if the lug holding it to the barrel is off by 1 turn.

I tried poking a 1/16" drill bit through the hole in gas cyinder, but it didn't go as deep as I expected. If it makes a difference, this is on a loaded M1a with a stainless barrel that is a little over a year old.

tia,
Bill
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #3 ·
Thanks - that helps. I didn't know if the hole in the barrel was large enough for a 1/16" drill or allen wrench to go all the way through to the other side of the barrel.
 

·
Registered
Joined
·
5,679 Posts
End of a big paper clip will get you to the same place. Make sure your gas valve is open (gas screw slot perpendicular to the barrel).
 

·
Registered
Joined
·
284 Posts
AT a minimum the 1/16th allen wrench or punch should go through the cylinder into the barrel. If it doesnt. You need to remove your gas plug then rotate your gas lock one turn either in or out to get the gas cylinder to align with your port.
 

·
Super Moderator
Joined
·
11,255 Posts
Sometimes people remove the gas system and when they reinstall it the gas cylinder fits over the barrel so tight that they think it's seated fully against the barrel shoulder but it's not. Take off the gas plug and back off the gas lock and see if you can get a wooden dowel or a small plastic hammer and tap the gas cylinder and see if it will seat farther back on the barrel.

Also, as suggested, flip the gas lock around and that may change the lockup of the gas lock so that the ports are aligned. Check to see if there's a noticable gap between the front band and the barrel shoulder or tell us if the front band is very loose.

Tony.
 

·
Registered
Joined
·
1,580 Posts
Is it possible to hit the gas cylinder too far back? I've tried several different gas locks and none of the tighten much. The best one starts to tighten right at the 6 oclock position.
 

·
MGySgt USMC (ret)
Joined
·
7,066 Posts
Is it possible to hit the gas cylinder too far back? I've tried several different gas locks and none of the tighten much. The best one starts to tighten right at the 6 oclock position.
Good question. On REAL M14's, the locks would almost never begin tightening up UNTIL they got to or beyond the 6 o'clock position. They were deliberately made that way by precise indexing of the threads. That way, you didn't have to have a "bucket of GC locks" as we Garand Armorers have to have.
 

·
Registered
Joined
·
7,984 Posts
It's kind of interesting that the gas port alignment doesn't have to be perfect in the M14.
The gas port is .076" if you want to check it with a gauge. However, the port in the gas cylinder itself is much larger than the barrel's gas port. This allows a certain amount of offset to compensate for thread timing as Gus pointed out. The military gauge used to check alignment is only .056". I guess as long as that will insert into the barrel port you should be good to go. If you can only insert a 1/16" Allen key there may not be enough space to allow sufficient gas to enter the gas cylinder resulting in short cycling.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #10 ·
It looked like it lined up ok, so I must not have cleanit it well enough. Now the piston moves up and down if I have the bolt open and point the barrel up and down. Using a scotch-brite on the piston may have helped.

I am thinking about getting some test tube brushes to clean the cylinder in the future - unless there is something that work better. A 10" by 0.5" diameter might be tight, but maybe I can cut the bristles down.
 

·
Registered
Joined
·
1,580 Posts
Any suggestions on what caliber brush for the cylinder? Thanks.
 

·
Super Moderator
Joined
·
11,255 Posts
I imagine a 50cal brush or one of them Glock nylon bore brushes would work fine. The gas system is pretty much self-cleaning in nature so the carbon buildup won't be that bad.

The inside diameter of the gas cylinder is .5000" to .5006".
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #14 ·
I was assuming that I need to clean the entire cylinder with the bolt locked to the rear and the hole the shaft of the piston fits in, but maybe that isn't a problem.
 

·
Registered
Joined
·
5,679 Posts
Lock your bolt back with a stripper clip. Pad your vise with a couple of wood blocks, lay front end of rifle in enough to give you access to the gas cyl plug. Get a can of carb cleaner and some large cotton patches. Hobby and home impv't dealers have 1/4", 5/16", and 3/8" fluted dowel rod that's cheap by the foot and works nicely with the patches to clean gas cyls and pistons if they're not calcified with carbon, in which case you need the drill bits. You don't want to score the inside of the gas cyl, just give it a good wiping out and removal of the carbon residue.
 

·
Registered
Joined
·
284 Posts
"I tried poking a 1/16" drill bit through the hole in gas cyinder, but it didn't go as deep as I expected. If it makes a difference, this is on a loaded M1a with a stainless barrel that is a little over a year old."

From this statement it sounds like your 1/16 drill bit is not freely passing through the gas cylinder completely into the barrel. If this is the case your need to adjust where the gas cylinder is by turning the gas lock...

unless the rifle is properly shimmed having the gas cylinder all the way back against the barrel may not be the proper location for your rifle to function. Proper function relies on enough gas getting from the barrel into the cylinder. Reread my post and others describing how to check alignment. It doesnt sound like you fully understand this.
 

·
MGySgt USMC (ret)
Joined
·
7,066 Posts
It's kind of interesting that the gas port alignment doesn't have to be perfect in the M14.
The gas port is .076" if you want to check it with a gauge. However, the port in the gas cylinder itself is much larger than the barrel's gas port. This allows a certain amount of offset to compensate for thread timing as Gus pointed out. The military gauge used to check alignment is only .056". I guess as long as that will insert into the barrel port you should be good to go. If you can only insert a 1/16" Allen key there may not be enough space to allow sufficient gas to enter the gas cylinder resulting in short cycling.
Ted, we used a 1/16" allen wrench to check alignment even on The Marine Corps Rifle Team rifles as a "down and dirty" quick way to do it. Never had a problem with any rifle short stroking due to insufficient gas and as you know, NM Ammo is loaded 100-200 fps slower than issue ammo.
 

·
Registered
Joined
·
1,580 Posts
Interesting, I thought match ammo was hotter than standard? Or are you referring to M852 vs M118?
 

·
Registered
Joined
·
7,984 Posts
Both M118 and M852 were loaded to about 2550 FPS. Military match ammo was loaded for consistant velocity regardless of the type of powder or powder weight.

My comment about using the 1/16" Allen key to check gas port alignment and that it may not be sufficient was mostly hypothetical. I too have used the allen key many times without problems. The again, I've found some rifles will short cycle even with 100% alignment. Every rifle is different. There is nothing wrong with using the 1/16" Allen key.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #20 ·
From this statement it sounds like your 1/16 drill bit is not freely passing through the gas cylinder completely into the barrel. If this is the case your need to adjust where the gas cylinder is by turning the gas lock...
It was ok when I tried a 1/16" allen wrench later. I must not have gotten the drill bit straight in.

I ordered the shim set today....
 
1 - 20 of 22 Posts
Top