Gas Locks & Gas Plugs - What am I missing here?

[KnickKnack]

Over on CMP there is a guy selling wrenches for gas locks and gas plugs. They look like very well made tools and will certainly do the job. However, when I install my gas locks, they do not fully tighten in a lined up postion. They go approximately 1/8 to 1/4 of a turn too far and I have to loosen them back to line them up with the cylinder. Is this normal? And if so, then why do I need a wrench? The gas plugs all were loose in the rifles when they came from CMP. I do tighten them down with a large screwdriver, but they seem to work loose after a few rounds of shooting. So which is correct? Should the plug be finger tight or wrench tight?

While I'm on the subject of the plugs, these are actually valves, right? But originally the straight slot ones were just plugs? Is there anything special you have to do to a GI gas plug valve or "poppit"?

[LEAD POISON]

Plugs tight.
Locks loose.
is right.

[timshufflin]

KK, as brother LP said, locks loose, plugs tight. You can use a BAS, 1/4" drive, or "the tool" to tighten the things but do make it tight. Here is a little diddy that I often find on rifles that come to me: I'll bet 9 out of 10 Garands mailed to my shop have the gas screws WAY to loose. That is, I hardly touch them with my BAS and they turn. A loose screw can cause all manner of problems including accuracy issues and short stroking.


One extra note, if you spray the threads of the screw with a little enamel paint, the screw stays put.

[Orlando]

The only time I ever had gas screws losen up is when using a combo tool or big screwdriver
I use a 1/4 inch drive extension and ratchet and never had one come loose since
My gas cylinders fit tight so the gas lock also fit tight
Optimal fit is a gas lock that lines up perfectly and times on the barrel shoulder. To get this you would have to have a whole pile of screws to search through
JMO
http://i47.photobucket.com/albums/f197/Garandlover/misc/MVC-003F.jpg

[KnickKnack]

Ok, thanks, that makes sense to me. I still don't understand why you need a lock wrench, then, unless you need to get a frozen one loose. I can't remember for sure, but I think they were all loose when the rifles came from CMP.

Would LockTite work just as well as enamel paint, Tim, or is that a no-no on guns?

[KnickKnack]

The only time I ever had gas screws losen up is when using a combo tool or big screwdriver
I use a 1/4 inch drive extension and ratchet and never had one come loose since
My gas cylinders fit tight so the gas lock also fit tight
Optimal fit is a gas lock that lines up perfectly and times on the barrel shoulder. To get this you would have to have a whole pile of screws to search through
JMO
http://i47.photobucket.com/albums/f197/Garandlover/misc/MVC-003F.jpg

That is a 1/4" extention, without anything on the end, just the square part inserted into the plug? It doesn't round the hole off?

[Orlando]

The lock wrench is to hold the gas cylinder when tightening the gas screw so not to put undo stress on the barrel splines.
If you tighten the gas screw properly you dont need anything on the threads

[Orlando]

That is a 1/4" extention, without anything on the end, just the square part inserted into the plug? It doesn't round the hole off?

Nothing but the extension, doesnt round off the hole as it fits perfectly. I have done it this way for years.
I didnt see any reason to buy a special wrench as I had this already in my toolbox

[The Garand Guy]

When you install the gas cylinder, it should not lock at the 6 o'clock position, but rather at 7 or 8 o'clock. The length of the front handguard determines this. You should screw the lock till it hits the shoulder on the barrel, then back it to the 6 o'clock position, & install the plug, tightly. This will place the gasport hole in the square cutout in the gas cylinder. A little Locktite will help. If the front handguard is excessively loose, you can epoxy it to the lower band. (This is not allowed for the John Garand matches, so you can pack the lower band with thin cardboard & remove it for the match.)
The solid plug was used early on; the poppet valve was introduced around 1944 for use with the grenade launcher.

[Orlando]

Tony ,
Please dont take this as I am arguing with you just trying to learn.
You said "
When you install the gas cylinder, it should not lock at the 6 o'clock position, but rather at 7 or 8 o'clock. The length of the front handguard determines this"

Why have a handgaurd determine where the lock should be?? I would much rather remove a small amount of wood off a handgaurd if need be to get approx 6 oclock fit. I have never had one off so much by removing wood that the gas port wont line up.
If gas port is partly covered it never seems to make any differnce in function anyway
I thought by having the lock against the shoulder it takes stress of the barrel threads?

[The Garand Guy]

When the lock goes to 7 or 8 o'clock. it is because the front HG is short. As I said, the lock should go past 6 o'clock , & then turned back in order to have some looseness in the front HG. There was an article in a recent GCA journal by bill ricca that quoted an Ordnance directive that the front HG should be slightly loose to allow for expansion when the barrel gets hot.
If you force the gas lock on, it will be too tight & will distort the barrel when it gets hot.

[Orlando]

Yes Sir we are on the same page. I agree there has to be some movement in the front handguard.
My point was I have had front handguards that were to long ( both commercial and USGI) and didnt let the gas lock go back as far as it should. IMO the handguard needs slightly sanded/shortened . I dont let the handguard dictate the position of the gas lock, I let the gas lock dictate the length of the handgaurd
Just the way I do it

[The Garand Guy]

You did the right thing.

[KnickKnack]

Thanks, Guys. This makes the reasoning a whole lot clearer. So I guess I am doing it right also, except not getting the plug tight enough. I'll definitely try the methods described here. :)

[melloman]

I bought the wrench. It was cheap enough and I have better leverage with it as opposed to a huge flat screwdriver. A plus is that it fits the gas lock screw perfectly, so no risk of damage to the screw.

[KnickKnack]

I bought the wrench. It was cheap enough and I have better leverage with it as opposed to a huge flat screwdriver. A plus is that it fits the gas lock screw perfectly, so no risk of damage to the screw.

Yeah, I like the looks of the gas plug wrench, was just curious why I'd need a gas lock wrench too, but now I understand the whole system better.

[timshufflin]

Okay, I'll chime in here a bit. My thoughts are not set in stone and are just thoughts but mine differ from conventional, here goes;
1. I could not care any less if my gas lock times at any point past the 6 O'clock position
2. I do care where the gas port lines up in the gas cylinder cut out, that's all I care about
3. I want my gas cylinder as far forward, towards the muzzle, as possible with the hole still showing in the cut out
4. I do this because I want the largest possible gas chamber to operate my rifle

I have had rifles that will not function with Lake City surplus with the lock timed per the status quo only to function fine when the lock is backed off another turn enlarging my gas chamber for full gas expansion. Think about Ole EricC on the CMP who sells those gas lock screws with the larger chamber in the head or the BM59 gas screws with the hogged out front, these screws allow for a larger possible expansion chamber and make some tired systems function that otherwise would not.