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 (please see Addendum at bottom) 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 this mod to any PWS owner.
Here are the pics of the gas valve after modification for visual reference:
Positions 1, 2, and 3 in sequence.
Addendum: Realized that the 1/16th (0.063") hole for Setting 2 was letting more has through than I wanted, so I drilled the second gas plug with a #55 bit (0.052"). Works just fine with steel cased Russian ammo, and of course brass cased stuff.
