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Thread: Sig556 Gas Valves

  1. #11
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    I sent CAA an email. We'll see if they respond.

  2. #12
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    I received a reply back. He said "It's not our product."

  3. #13
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    I purchased a 0.011" to 0.060" gage pin set, so I'll be able to let y'all know spot on what the hole sizes are.

  4. #14
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    i'm interested to see how this turns out for you. i picked up a 4 position gas valve a year or two back from the guy doing the conversions on the sig556 forum. while it is better i wish the suppressed port was smaller.

    what gas port sizes were you thinking about drilling ?

  5. #15
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    I don't know. I figure that I can start small and enlarge them slowly as necessary.

  6. #16
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    I bought an extra valve years back for my 556R and someone drilled another hole and notched the valve for a suppressor setting. Never thought to check the original holes. Maybe some valves are for 556r and some are 556?

  7. #17
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    Quote Originally Posted by ndmiller View Post
    I bought an extra valve years back for my 556R and someone drilled another hole and notched the valve for a suppressor setting. Never thought to check the original holes. Maybe some valves are for 556r and some are 556?
    I have an extra valve for my 556R for this exact purpose. I've never done it though. Do you know the size of the suppressed port?

  8. #18
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    My 5.56 SBR is built off the pistol and stocked.
    Is the rifle valve different than the pistol valve?
    “Where weapons may not be carried, it is well to carry weapons.”

  9. #19
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    I don't think so. The valve in my 556 Classic is silver, but it was made before my 556 SBR. Perhaps they just changed the finish along the way.

  10. #20
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    I received the gage pin set today. I'd say it's well worth the $25.45 for those who are interested measuring gas port holes that are less than 0.060" in diameter.
    https://www.ebay.com/itm/131871027927

    Below are the measurements of the five gas valves that I have.

    556 Classic valve (silver in color)
    Large hole: 0.053"
    Small hole: 0.050"

    Original 556 SBR valve (marked E opposite UP designation)
    Large hole: 0.054"
    Small hole: 0.051"

    New valve from Sig USA packaging (marked A opposite UP designation)
    Both holes: Over 0.060"

    New valve from Sig USA packaging (no letter designation opposite UP designation)
    Large hole: 0.049"
    Small hole: 0.047"

    553R LB valve (marked 12 13 14 15 on face)
    Largest hole (15) : 0.058"
    Next hole (14) : 0.053"
    Next hole (13) : 0.050"
    Smallest hole (12): 0.046"

    Based on my small sample size of three measurable Sig USA valves, I find it interesting that the diameter difference between the small and large holes is always 0.002" or 0.003". I think that kind of discredits the theory that someone was simply drilling holes of random sizes in the valves. Given that they were able to be consistent with the diameter differences between the holes on the same valves, then why are there such large differences between the holes located in the same place on different valves (large vs large)? Finally, do the letters on the Sig USA valves mean anything?

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