Impact X Losing Power at Higher Reg Pressures

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mtnGhost

mtnGhost

Member
Dec 15, 2018
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Defected from the PNW, United States
Last night, out of no where I started seeing issues with power loss at higher regulator pressures. I depressurized, turned the reg back down to one full counter clockwise rotation, repressurized, and my (Huma) gauge read a hair under 100bar (This gauge is around 5-7bar short than actual pressure). From there, I turned up the pressure to around 125 bar (actual) and tested a 23gr NSA with my chronograph and it was slow.

I backed out the valve adjustment knob all the way, and for a few shots - it appeared that the problem was fixed. This knob has also been a little problematic for me since I've had this rifle. I started adjusting my reg back up from 125 in ~3 bar increments, and everything over 135 bar showed that it was on the downslope of the power curve. I can actually hear the weakness of the shots.

Im not sure what the isssue is, I swapped the 22 barrel out for my 30 cal and it's the same behavior - it just doesn't have the umph anymore. Does this ring a bell for anyone? I've got it opened up tonight (I wanted to get a feel for the hammer and internals)..

1550889729_7837327595c70b30161fab6.77046760_B4CF9619-EAAD-4761-ADE4-337A5C8B5092.jpeg

 
I have a 30 cal impact x and the same thing happened with mine after about 400 shots. I took it part, cleaned everything put it back together and it was fixed. I found a lot of little aluminum shavings inside the valve housing. Im guessing a shaving was stuck and riding against the valve rod and making it hard to move. Also i had no set screw in my valve rest either. It is just loctited on.
 
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my limited experience, this was happening from the get go for me, my hammer spring was set at 21 mm and not the recommended 18.5 for a 22. soo maybe see if you can tweak that up a bit? unless your already maxed out in which case I have no idea....
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Yeah I maxed it, no slop.

A few things I've observed ..

  • Ernest talks about the valve seat in this video around 4mins in https://m.youtube.com/watch?v=HDCIyO9mxmg
  • My valve housing is in there pretty good, like REALLY good. The first thing that I noticed after taking off the top plate was my entire rear action via the long black valve tube was turning freely. There's a big socket cap screw right above the rear top of the pistol grip area that looks like it's suppose to keep the tube tensioned down, whoever assembled this Impact must not have cared much and they just Loctite'd the crap out of it without making sure it was secured.

I'm not sure that I want to put the tube in my vice to get the housing off right now. I have a decent enough visual on the valve seat to see that it looks in tact all around.

Nothing else that I'm seeing appears to be worn or broken.
 
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I had similar experience with my FX Impact X 700mm - it was due to me backing out the valve control knob too much. Turned the valve knob back in to about stock settings of about 3.5/4 lines and try again. From my experience, it is not true that one can/should turn the valve control knob all the way out.
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Yeah, this is the conclusion that I'm coming to now. The thing is really screwy (no pun intended).. I buttoned it back up, turned the reg to 147'ish, and was getting 557 with a quiet "poof" (50.15gr JSBs). I screwed it all the way in, then backed it back out to a hair over the 4th line - next shot was 856fps.

I guess I was braced for the worst, but it made a good use of my evening to learn the internals (and do some cleaning / slightly unnecessary o-ring maintenance).
 
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I'm half tempted after all of this to put a 1/2 drop of Loctite on the screw that goes into the threaded sleeve that holds the valve stop ball. It might be a PITA getting the sleeve removed if I went overboard, but just enough to keep it mated would be ideal.

Anyone else done this?
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Purple loctite or better yet permatex ultra black rtv sealer to stop things vibrating out.

I never used the valve stop adjustment for .30... I kept it way out past the 4th line. I do use it for .22 to keep from wasting air and be a little quieter.
 
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My 2 cents

If the c3 bumper is different than factory, that will affect how the knob works, I can see a green oring there, not recommended, since also affect hammer performance (too soft or thick) and might lower your spedds as I recall ER told me once (normal orings not recommended) too much cushion. Green orings are too soft (70) you need at least 90 or more

You probably did it but I saw no mention to the spring tention screew. That one needs to be adjusted and also get loose sometimes after several shots

What I use instead of loctite is teflon tape / ptfe , on the parts that get loose (spring tention screew and in that rod end, both can get unscrew easy, and tape works perfectly, much better than any screw lock if you change barrel a lot on the hammer spring screw at least.
 
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