I recently purchased a Sig 556 Pistol with the intent of turning it into an SBR project. Took it out to the range to break it in and the thing is WAY over gassed. Brass is ejected almost 40', the case mouth is destroyed, body is dented, and the ejector is nearly tearing the cartridge rim off.

I do my research and find out this is pretty much common place for the rifle. Sig customer service doesn't consider it an issue and won't do anything about it. There is a little know solution of drilling new gas ports into the gas valve and retuning the pressure to a reasonable level. The issue there is that the part is made out of very hard steel and the quotes I got from my local machine shops are all over $250.

So I say enough is enough and decide to take this project on myself. I am in the process of tooling up and I have secured a small lot of original Swiss Sig SAN gas valves to offer these to other people who are having this issue.

The new valves will keep the rifle from destroying brass (for those who reload) and this is ideal for those who are running suppressors on their Sigs (suppressing the rifle exacerbates the problem).  It also prevents the bolt carrier from slamming into the back of the lower receiver with unnecessary force, so it smooths out recoil and saves wear and tear on the gun.  

If anybody is interested, I have included an order form below that you can fill out to hold a spot in line.  Email the form to the address written on the bottom of the order form.

As of right now I have about 8 other guys who are placing orders. Time line is about 4-6 weeks right now to allow for the rest of my tooling to show up, the Swiss parts, and to allow for some testing before they ship.

Price will be $150 shipped or $105 to have your own valve drilled and shipped back.

I will offer a $40 core charge refund for those who decide to purchase a new valve and ship back your original.

If you cannot print, fill out, and rescan the order form to me, you can just type the information into an email.

The address is CBUELL77 (a) yahoo
I realize it didn't come out very clearly*

If you have any questions, please feel free to post them.

Cheers!
Chris


This list shows the initials of the people I have received order forms from:

1. CS
2. SO
3. DB    
4. MA
5. LD
6. RM
7. SC
8. WS
9. BD
10.DA
11.GG
12.KA
13. WJ
14. RP
15.
16.
17.
18.
19.
20.

Are you willing to work on 556Rs?

i'm definitely interested in one of these

email inbound with a couple of questions

is there a way for you to make one of them exactly like a 4 position factory 553 plug.  if there is then I am in.

Depending on what you mean by "exactly," yes.  

The valves would come with the factory "normal" and "adverse" on one side drilled by Sig and on the other you can choose between "off" "suppressed" and "improved normal" for the other two positions.

Fill out an order form and send it in to CBUELL77 (a) yahoo to reserve a spot for yourself on the list.

Yes I am. I don't have one to test. So worst case I start conservative and if it needs a bit more gas to run reliably, I'll just redrill it for you for free.

There was a post over on Sigarms556 with info I'll see if I can find it. I won't be able to send you mine until next month, but I'm in to have one drilled for a 556R


Edit, I'm in for one. I'll just buy a SAN valve you have redrilled. Still won't be able to buy till next paycheck (2/16)

So you are doing the detent modification as well? If there an extra charge for the 4-Pos?

Sounds good. Get an order form in now to hold your place in line.

It's going to be 4-6 weeks for everybody. No need to pay until closer to the shipping dates.

Correct. All of these are effectively going to be 4 position valves. 2 positions from the factory, the other 2 of your choosing. And yes, the valves will come already detented for all 4 positions.

i'm in , email inbound

Some number and pics of gas valves.

Port sizes / I am assuming those are what is marked in metric values (MM).

0.9mm = .0354
1.2mm = .0472
1.3mm = .0511

Fun with some numbers using a Gas flow thru orifice calculator.

Based on a barrel / port pressure of 55,000 PSI and a flame temperature of 3300 F the flow for the various gas port diameters comes out as follows:

0.9mm / .035 diameter port = SCFM flow rate of 301.7
1.2mm / .047 diameter port = SCFM flow rate of 536.3
1.3mm / .051 diameter port = SCFM flow rate of 629.47

The 1.2mm port is the "standard" and the 1.3mm port is severe duty.
The 0.9mm port is the assumed suppressed port setting which shows a marked reduced flow rate.


The calculator I used is online ~

http://www.tlv.com/global/TI/calculator/air-flow-rate-through-orifice.html



SIG factory valve~



Note cut  for orientation ~




Modded 556 factory valve (mine)

I'm in for a pair of 556s and a 553. Will try and get you my order today.

Need one for a 10 inch SBR with Suppressor
Email sent!

Are the valve ports different for a 10'' gun vs a 16'' gun. Both are 7'' twist.

I know I'm in on a 16'' valve.

How are you going to get all 4 positions on a original valve?

I take it the Swiss valves are not drilled, correct.

As long as they are 1/7" the 10" and 16" should be close enough to run the same port sizes.

No the Swiss valves are coming drilled with two ports.  People who order one of these improved valves will be able to add two additional positions with port sizes of their choosing.

Also, if you are interested in one of these valves, I would suggest getting one of the order forms email sooner than later.  Most of the valves I have coming in are now spoken for.

I have edited the first post to show the initials of the people whose order forms I have received.

Here is a teaser for those who have been waiting patiently.

Note the difference in the brass.  The brass on the left is using the stock normal position, brass on the right is from the improved valve.

I sent out a test valve to a member who has the ability to test things out with a suppressor.  Pending his results, I'll be able to start cranking these out for everyone.

that's about what my brass looks like on the left.   although mine don't usually have the dent in the side of the case just the case mouths crushed.  i'll have to dig some out and look at them.

thanks for the update.  after seeing the pictures of the brass i'm anxious to try out the new valve

None of the three (3) 556 rifle I have owned bent case mouth's like you have pictured and I run a suppressor on mt SWAT 556.
I will still mod one of my gas valves to tune some carrier velocity down but your rifle appears to punish the brass far worse than any 556 I have fired.

op is nonpaying dealer previously warned and now locked