Another SIG 556 problem discovered- Gas valve ports reversed

[Kisara]

We all know about the numerous different types of QC problems documented about the Sig Sauer 556. Here is one I discovered while disassembling a 556 made in 2009, and I don't believe anyone else has brought it up before. I chose to post it here at M4carbine.net, since this forum's users take their weapons more seriously so to speak than forums whose member base consists mainly of casual/recreational shooters.

First, the function of the gas valve on the 550 series needs to be briefly explained. The valve has two positions, one for normal shooting and one for when the weapon is fouled (or frozen with ice) to the point of not cycling. This second position is also sometimes referred to as the "Emergency" setting, and lets much more gas in to act upon the piston to dislodge. The gas pressure in this position is so strong, the manual (Both US and Swiss) caution NOT to run the weapon in this position unless absolutely necessary due to the added stress on the parts.

From the Swiss manual:


The valve has two ports, the smaller one for the normal setting and the larger is obviously for the fouled/emergency setting. On both sides of the gas block, there are downward venting exhaust ports (Located between the roll pins) :



The smaller gas valve port is directly underneath and in line with the exterior rib, which during normal use is in the vertical 12 o'clock position. The smaller port lets in less gas from the barrel into the system, and at the same time the larger gas valve port will exhaust excess gas out of the left side of the weapon. Switch the rib to the emergency setting, and the larger port is now inline with the barrel. Obviously the larger hole lets in more gas, but the smaller port now does exhaust duty out the right side.

So its not just a matter of having small or large inlet ports to choose from for letting gas in from the barrel, but you also have a smaller and larger exhaust port as well. And the only choices of this combination are "Small intake, Large exhaust" or the brutal "Large intake, Small exhaust."

Here is a photo I saved that was posted about a year ago on another forum of a Swiss gas valve. I do not remember the poster's name, but if you are here shout out and I'll give you due credit. Notice the normal (Small) port on the left, larger on the right.



And here is what I found when I compared my own Swiss 551 valve (left) next to the US made 556 valve (on the right) :




I don't have access to any tools or even drill bits small enough to measure the port sizes. One person I showed the photo to thought it was somehow an optical illusion, so I verified the size difference with a sewing needle.



Obviously I think it would probably be a good idea for 556 owners to check their valve ports before the excess wear and tear of unknowingly shooting in the "Emergency" setting takes its toll.

[Reagans Rascals]

Did you like the rifle when you fired it? Did you experience any malfunctions? I really like SIG and I appreciate your post, it has shown me a lot before a purchase, would you purchase it again knowing what you know now?

I can tell the port sizes are different in one of your photos so its not an optical illusion.

[Dirtyboy333]

That's ridiculous that they can't even drill the right size ports in the right place.

I'm actually drilling new ports for mine on the flip side (see the 55x sticky at the top of this sub forum) and while researching the project I talked to a guy who has a bunch of extra valves laying around from conversions that he will sell.

He told me to contact him on Saturday to purchase and once I get the details on price etc. I'll let you know if your interested.

[scottryan]

Tag for later review.

[dwhitehorne]

Well that is interesting. I've got about 1800 rounds through mine without any issues. I'm going to have to go home and check to see. Other than cleaning it a couple of times, I have never really payed any attention to the valve. David

[SteyrAUG]

Just...wow.

[SteyrAUG]

Originally Posted by Dirtyboy333

That's ridiculous that they can't even drill the right size ports in the right place.

I'm actually drilling new ports for mine on the flip side (see the 55x sticky at the top of this sub forum) and while researching the project I talked to a guy who has a bunch of extra valves laying around from conversions that he will sell.

He told me to contact him on Saturday to purchase and once I get the details on price etc. I'll let you know if your interested.

Wouldn't it be much, much easier to simply order a correct Swiss made one?

[Moose-Knuckle]

SO thankful I sold my 556 off and got what I had into it!

[variablebinary]

Not surprising.

If SIG USA can't get the big simple things right (rail alignment, finish, proper fitting furniture), then there is no way in hell the little, vitally important details & things are done right.

[Dirtyboy333]

Originally Posted by SteyrAUG

Wouldn't it be much, much easier to simply order a correct Swiss made one?

Yes that would be much easier........BUT i don't know where to get them. CO Arms sells the whole piston system but its so damn expensive and im not really worried about converting my 556 into a 551 or such. I would like to, but weighing the cost/benefit for my needs its not nearly worth it.

Why, do you know of some that are for sale? That would be great!!!

Also, theres a couple of pics floating around of the regulator from a STGW90 (i think) and the GP's on it were slightly larger than mine. I want to be smaller.

ETA: The pictures i mentioned are in this original post but ive seen it other places prior to this

[Rayd8]

Thank you for posting this...seems like this would've been brought to Sig's attention. Have you shown this to them? Have they responded? Seems like a recall issue.


Thanks again!

PS - Go Steelers!

[RogerinTPA]

Absolutely incredible. So much for their QC. IMHO, that company's quality has been slipping for years.

[Kyohte]

Interesting. I've got mine pulled out and I'm going to go measure the two holes. My 556 has a significant round count, but doesn't show any excessive wear. Do you think the hole might be eroded, or was it like this from the factory?

Also, if you get in touch with the guy who has extra's, let me know. Regardless of whether or not mine has problems, I like having spare parts around.

[Kyohte]

If the hole sizes are indeed 1.3mm and 1.6mm I having a hard time distinguishing them through measurement. The right hole looks smaller (i.e. incorrect), but I don't know if I can accurately perceive a 0.3mm difference. It is certainly not as obvious as in the pictures. I don't have a needle large enough to try the needle trick.

This Sig was made in 2006 if I remember correctly.

ETA: The piston assembly on Colorado Gun Sales website that includes the regulator is American made, not Swiss (you can tell by the piston). The Swiss assembly does not include the regulator.

[Dirtyboy333]

Originally Posted by Kyohte

If the hole sizes are indeed 1.3mm and 1.6mm I having a hard time distinguishing them through measurement. The right hole looks smaller (i.e. incorrect), but I don't know if I can accurately perceive a 0.3mm difference. It is certainly not as obvious as in the pictures. I don't have a needle large enough to try the needle trick.

This Sig was made in 2006 if I remember correctly.

ETA: The piston assembly on Colorado Gun Sales website that includes the regulator is American made, not Swiss (you can tell by the piston). The Swiss assembly does not include the regulator.

Oh ok, thanks.......Yeah i don't know where to get a swiss regulator but i don't even think i want one because the ports will be larger than what i already have.

Im supposed to email him tomorrow (Sat) morning and he is actually going to take the time and measure for the valve with the smallest GP and sell it to me (seems to be a very nice guy). I don't yet know the price or even have an idea of what their worth but being that their Sig USA regulators i don't plan on buying 1 unless its within $60-$70 and I feel thats even generous but i could be way off.

I'm VERY interested to know what size ports you have because my uncles is also an early 556 serial JS 006xxx and his has the .045" port that i want. I'm wondering if yours also has the smaller port compared to my newer 556 with a .052" port. Wonder if Sig USA enlarged them to correct some type of cycling issue?

An easier way to tell which port is smaller with the naked eye is to take the piston tube (?) out and look at the two gas ports thru the bottom of the piston tube. Its easier to tell bc of the area between the edge of the GP and where it meets the tube.

[Kyohte]

Mine do appear to be reversed, but the size difference is very small. I will be trying to dig out the calipers later today. Last night I could only find stuff measuring in fractions of an inch, and I could only tell that the ports are somewhere between 1/32" and 1/16". The measurements 1.3mm and 1.6mm fall in between those as well.

[JDW67]

Originally Posted by Moose-Knuckle

SO thankful I sold my 556 off and got what I had into it!

You're one of the lucky ones. A lot of people who bought when they first came out at around $1,600 are fuming...

[Kyohte]

Originally Posted by JDW67

You're one of the lucky ones. A lot of people who bought when they first came out at around $1,600 are fuming...

What pisses me off is the missed potential of the 551. I love the design of the weapon and feel with some minor improvements that it could be a serious competitor to guns like the SCAR. The 556 was a step backwards.

I paid 1400 for mine in early 07. Since then I've tinkered with it and changed out some parts, etc. It has been a good gun, not worth the cost, looking back, but it has provided me with enjoyment. All my other guns fill the "serious" role, so problems with my Sig don't bother me too much (and give me something to try and fix).

[SteyrAUG]

Just a thought, since they seem to be reversed, why not just run them in the reverse positions?

I am also wondering if this maybe accounts for some of the many failures encountered during serious training.

[Kyohte]

Originally Posted by SteyrAUG

Just a thought, since they seem to be reversed, why not just run them in the reverse positions?

I am also wondering if this maybe accounts for some of the many failures encountered during serious training.

This is the most likely solution. What I want to know is if they are the right size either way.