Air Venturi Avenger went auto..?

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EmptyTin_Tim

EmptyTin_Tim

Member
Dec 8, 2022
455
306
Midwest, USA
Hey guys

I have a modded normal Avenger. 22 that just made "full auto" noises like when a paintball gun or CO2 airgun are on last bits of air... went brrrrrrr like shot real fast back to back to back and watched the needles drop then rise again when it was done.

It has a light valve poppet spring and some other stuff done to it but it has stock hammer spring set at 4 turns I think.

Any idea what could cause this on a side lever gun? It did it twice in a magazine but not back to back.

Need new poppet or something? I didn't mess with hammer spring or regulator but did recently have to degas to replace an O ring on the plug for the bottle conversion. No idea why that would matter but just giving more info.

Thanks in advance!
 
It worked perfectly fine for 5 months after the mods.

The reg is set to 2.2k and that's about where it's been since mods were done. I hadn't adjusted the hammer spring for the 5 months either.

It does sound like hammer bounce would be suspect but I don't understand why it would do that once and then fire fine for 10+ more shots then do it again then be fine for more shots. If it were due to hammer bounce it would do it all shots after a certain regulator pressure, correct?
 
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Long shot possibility but if the valve stem is experiencing blow-by, the air pulse can send the hammer back, recompress the hammer spring, and send it back at the stem, causing it to knock the valve open again. And although I regard this as a long shot possibility, it would match the intermittent symptom you're seeing because blow-by tends to be a bit erratic.

Another possibility is that the amount of hammer strike has unexpectedly changed. The usual reason being that the adjuster moved (self-adjusted). But another possible reason is a little more covert, which is if the stem gets hammered a little deeper into the poppet over time, the result is equivalent to increasing hammer stroke, which will produce a harder strike. Either way, this is probably an easy one to rule out by breaking out the chronograph and re-finding the velocity plateau and then backing it off to the ~97% mark.

Lastly I'll just say I learned the hard way that using a soft valve spring is a pretty low benefit / high detriment strategy in the vast majority of situations. Meaning it yields only a small benefit in terms of increasing dwell or reducing the amount of hammer strike required, while compromising the ES and making the gun more susceptible to hammer bounce.
 
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Intermittent suggested something is changing state in one condition but not the others, ie: stem ejects itself some from the poppet, resulting in pre-compression on the hammer spring which introduces hammer bounce, and then the stem gets re-seated back into the poppet, until it comes loose again. Not saying this is what you're experiencing, but explaining how a conditional state change explains your intermittency.

-Matt
 
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Very interesting suggestions. I didn't have the chronograph out but was working to sight in some 20.2 NSA .2165 so I don't know if it was off the knee that I know I had tuned it to months ago. It didn't sound any louder than before to suggest the hammer strike increased. My notes say they were going 950 ish fps before so I'll have to see if they are way off that now.

Sounds like I'll have to get a new poppet /valve stem to really fix this if it is failing somehow whether from blow by or the actual stem is loose now.

spring kit The light spring I installed wasn't just off the shelf it was from a kit. I definitely saw improved speeds from the lighter spring and the heavy hammer spring was actually too much it was basically as strong on zero or 1 turn in as the stock one at full in so it was violent and definitely wasted air at that pressures so I had put the original back in but have the light valve spring in there.

(This is with barrel port at 5mm but) I remember I was testing different tunes and ammo and the 17.5 nsa was consistent at 1018 fps average with 2.2k reg and 4.5 HS
4.5 HS 1018, 1022, 1013, 1022, 1023, 1020, 1013, 1015, 1022, 1020,
Ave @ 4.5 1018.8
FPE 40.34

So I'd have to see if this tune is still consistent or if it is wild now. It should be the same tune as I don't think I changed it since May.

I don't think I damaged it but it is possible that when the o ring leaked and it was stuck at 1k psi or so , I was dry firing it down until it leaked out the rest so maybe then it hurt the poppet?

Maybe I should put the oem poppet valve spring back in but at that point it would be apart enough to replace the poppet too so probably should wait til I get that replacement.

I'll have to see if Pyramyd sells the poppet.

Thank you!
 
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Hey guys I have a little update. So my Avenger squished out an o ring and I need a replacement, need to know the size I posted about here https://www.airgunnation.com/thread...e-plug-o-ring-for-bottle-adapter-kit.1321150/

Anyway since it was out of air I decided to pull it apart and get the poppet under inspection.

Poppet is totally fine. I think the issue is the lighter replacement spring is not ground flat. The spring must rotate certain times of shooting and the coil hangs up the poppet and makes it stick sideways. See photos
20241019_162942.jpg
20241020_155718.jpg
20241020_155634.jpg

So I am going back to original spring.

Hoping this stops the brrrrrt air dump!
 
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