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Thread: PWS MK1 Gas Valve Modification

  1. #1
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    PWS MK1 Gas Valve Modification

    Figured this needed it's own thread to make it easier to find for anyone doing a Google search.

    Bought my PWS Mk116 Mod 2 last year and have really enjoyed it, despite being a bit too busy to shoot as much as I had originally anticipated.

    Nonetheless, I did learn that it's gas settings needed a bit of...um...tweaking. Position 1, the one recommended by PWS for non suppressed use, has a huge orifice and is seriously overgassed. Position 2 uses a 3/64" (0.047") port, and is the suppressed setting PWS suggests if Position 3 is too sluggish.

    Fortunately, Position 2 actually works very well with full power, brass cased ammo, but tends to choke with the weaker steel cased Russian stuff. The rifle shot so softly compared to P1, so I determined that I'd find a way to make it work for me by opening up the port a bit.

    I called PWS to order a spare gas valve knowing that having a spare invokes the law of the universe that guarantees you will only need the spare if you don't have it. Surprisingly, PWS was nice enough to send me one for free. Sweet. Knowing that I could now no longer possibly screw up the gas valve in the rifle, I started drilling... And drilling... And drilling. After trying every type of 1/16" (0.063") bit I could find locally, I realized that I was going to need something WAY harder. Turns out the valve is nitrocarburized, and nothing I tried even left a mark.

    After a bit of research, I learned that what I probably needed was a "solid carbide" bit. I ordered it online and after a few days, I was able to open up the port with ease. Nice, but what was I going to do about P3? It's not really a port like the other two positions, but a channeled indent in the gas valve leading to a half circle notch which allows a tiny amount of gas to squeeze by and cycle the system. I figured that I only needed a small hole in order to get it to cycle full power ammo, so I initially ordered a 1/32" (0.031") solid carbide bit.

    Snapped like a glass rod the first time I tried to use it. Doh! So I ordered a 1mm (0.039") bit which ended up doing the trick.

    So now I can run standard full power brass cased ammo, 223 and 5.56 in P3. Russian steel cased and up in P2, and then P1 is relegated for emergency usage. I love how soft shooting the rifle is now, and recommend my mod to anyone fortunate enough to be a PWS owner.

    Here are the pics of the gas valve after modification for visual reference:
    Positions 1, 2, and 3 in sequence.
    Attached Images Attached Images
    Last edited by georgeib; 05-04-18 at 18:08. Reason: Added conversion to thousandths

  2. #2
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    Here are some comparison pics with the OE gas valve.
    Attached Images Attached Images

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    Very cool! I wish I knew of a way to do the opposite. I have the MK111 Mod 2 and its horrendously overgassed. Running it in the suppressed setting with a Specwar 556k its still vicious. Even with the vltor A5H4 buffer. So much so, I don't like running it with a can.

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    Quote Originally Posted by msnyder0609 View Post
    Very cool! I wish I knew of a way to do the opposite. I have the MK111 Mod 2 and its horrendously overgassed. Running it in the suppressed setting with a Specwar 556k its still vicious. Even with the vltor A5H4 buffer. So much so, I don't like running it with a can.
    Interesting. Is that even in position 3 on the gas valve?

  5. #5
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    Quote Originally Posted by msnyder0609 View Post
    Very cool! I wish I knew of a way to do the opposite. I have the MK111 Mod 2 and its horrendously overgassed. Running it in the suppressed setting with a Specwar 556k its still vicious. Even with the vltor A5H4 buffer. So much so, I don't like running it with a can.
    Might be worth asking if they'll send you a blank gas valve or maybe just send it in for them to fab one for you; the CS guy I spoke to has mentioned they've done this in the past. That being said, when I sent my gun in recently (undergassing unsuppressed with a Vltor A5, Sprinco Green, and A5H2 while using 62 gr Gold Dot), they said that it was not excessively gassed on the fourth position (MK110 Mod 1), even though I feel that I get way more gas to face with my MK110 and SureFire SOCOM556-RC compared to my custom 11.5" (0.063" Black River Tactical gas port insert, A5H2, Springco Green, LMT e-BCG) with the same can.
    Plus ça change, plus c'est la même chose.

    老僧三十年前未參禪時、見山是山、見水是水、及至後夾親見知識、有箇入處、見山不是山、見水不是水、而今得箇體歇處、依然見山秪是山、見水秪是水。

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    Quote Originally Posted by Defaultmp3 View Post
    Might be worth asking if they'll send you a blank gas valve or maybe just send it in for them to fab one for you; the CS guy I spoke to has mentioned they've done this in the past. That being said, when I sent my gun in recently (undergassing unsuppressed with a Vltor A5, Sprinco Green, and A5H2 while using 62 gr Gold Dot), they said that it was not excessively gassed on the fourth position (MK110 Mod 1), even though I feel that I get way more gas to face with my MK110 and SureFire SOCOM556-RC compared to my custom 11.5" (0.063" Black River Tactical gas port insert, A5H2, Springco Green, LMT e-BCG) with the same can.
    Thanks, I just may do that. I've heard the Mod 1's were a bit lighter on the gas than the mod 2's. On mine, in the wide open setting, unsuppressed I can easily run wolf steel with a Vltor A5H4 buffer all day long.

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    Cool stuff... I guess they tweaked it. I had one of the original Mod 2 uppers, thing would hail mary wolf gold brass on setting '2' with a sprinco red! Setting '1' was pretty gassed as u can imagine. After the gasblock cracked where the knob goes, I sent it in and they replaced the ENTIRE upper since they couldn't get the GB off... now it'll eject the same ammo a little front of 3:00 on setting 1 with a sprinco red, and short strokes on '2' with an extra power jp spring. Still nice to know that if I ever come to my senses and shoot bulk steel case, I'll have a good piece to do it with. peace

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