Air Venturi Speed estimate

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GerrywithaG

GerrywithaG

Member
Aug 18, 2021
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PA., United States
HI everyone.
I am having an issue with my Chronograph reading too fast, I think? While I am waiting for a replacement I need some help. My .22 Avenger reg is set at 1700 psi with "0" hammer spring and I am reading 955 fps shooting 18.13gr. JSB heavies. This is my 2nd Avenger and from what I have experienced before at those settings, I should be seeing maybe 750fps-ish. Normally I would need to run 2200 to 2400 psi, and 2 to 4 turns in on the hammer spring to get 950fps.

If you have an Avenger, what should the following settings give in f.p.s. roughly?

JSB 18.13's, 1800 reg, 2 turns in h.s.

JSB 15.89 Hades 1600 reg, 0 turns in h.s.

H&N Cuda s 2400reg, 3 turns in h.s.

Thanks for your help!
Gerry
 
You definitely have an issue. Your estimate is probably very close. I modded my Avenger too quick to remember stock settings' fps #'s but I think you may have a stuck hammer spring or something? Try running it all the way in and then back out again just to make sure. I'd shoot it at each turn out just to make sure fps goes down. I mean, also easy way to check is the HS all the way in there's some effort to cock it where at 0 that's super easy. But youd know from your other Avenger.

Have you de gassed and turned the reg screw in all the way and re started that reg set process too? Maybe reg psi gauge is broken. Could swap it out while degassed with other side to test.
 
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GerrywithaG said:
My .22 Avenger reg is set at 1700 psi with "0" hammer spring....
Click to expand...
I too have the regulator on my .22 set to 1700psi, and found the hammer spring did not have sufficient adjustment range to back it off to the velocity knee. The result was excessive muzzle blast and mediocre groups. Removing one coil from the spring allowed me to get it adjusted to about 97% of max velocity. Air usage is much better and groups improved noticeably.
 
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EmptyTin_Tim said:
You definitely have an issue. Your estimate is probably very close. I modded my Avenger too quick to remember stock settings' fps #'s but I think you may have a stuck hammer spring or something? Try running it all the way in and then back out again just to make sure. I'd shoot it at each turn out just to make sure fps goes down. I mean, also easy way to check is the HS all the way in there's some effort to cock it where at 0 that's super easy. But youd know from your other Avenger.

Have you de gassed and turned the reg screw in all the way and re started that reg set process too? Maybe reg psi gauge is broken. Could swap it out while degassed with other side to test.
Click to expand...
Thanks for the ideas Tim! over the weekend I was curious about the reg. Having slow recovery after a shot, so I went into the shop and turned a Plenum. It ended up being 17.5cc and seems to be helping the shot cycle recovery. I didn't take the hammer, or spring apart because the gun does take adjustment fine, and has 5.5 turns in/out. I am thinking my Chronograph is wonky. I did take the Chrony apart (it's an inexpensive one from eBay) and move the sensor lights further apart thinking it would see that as the pellet going slower? Seems to have taken @25fps off, but I am making so many changes....I need to start from a new baseline in the morning, and go from there. Through all this, the gun is shooting great groups, so it's all working so far.
Thanks again Tim! Here's a pic of the Plenum. I need to clean my shoting bench!
IMG_20241006_200418_718.jpg

Gerry
IMG_20241006_200418_718.jpg
 
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nervoustrig said:
I too have the regulator on my .22 set to 1700psi, and found the hammer spring did not have sufficient adjustment range to back it off to the velocity knee. The result was excessive muzzle blast and mediocre groups. Removing one coil from the spring allowed me to get it adjusted to about 97% of max velocity. Air usage is much better and groups improved noticeably.
Click to expand...
That's an idea there Nervous. I don't think it can hurt taking a coil off the spring....better yet, II'll find replcement, and keep thefactory spring intact. Thanks for the idea!
Gerry
 
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GerrywithaG said:
Thanks for the ideas Tim! over the weekend I was curious about the reg. Having slow recovery after a shot, so I went into the shop and turned a Plenum. It ended up being 17.5cc and seems to be helping the shot cycle recovery. I didn't take the hammer, or spring apart because the gun does take adjustment fine, and has 5.5 turns in/out. I am thinking my Chronograph is wonky. I did take the Chrony apart (it's an inexpensive one from eBay) and move the sensor lights further apart thinking it would see that as the pellet going slower? Seems to have taken @25fps off, but I am making so many changes....I need to start from a new baseline in the morning, and go from there. Through all this, the gun is shooting great groups, so it's all working so far.
Thanks again Tim! Here's a pic of the Plenum. I need to clean my shoting bench!View attachment 502412
Gerry
View attachment 502412
Click to expand...
Wow that's great work! Wish I had a shop could make a plenum! I bought mine.

You could try this chronograph I have been using for 2 years.
 
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EmptyTin_Tim said:
Do they actually swap over? I know the Avenger and Avenge X barrels are not compatible
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Thanks for the kind words Tim. About the s/s regs. From what I heard they will fit, but the safety cross pin may have to be re-drilled as the s/s reg is alittle longer. I have a Regulator on the way from Air Ventury whenever they are back in stock!?
 
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Yeah the potential for galvanic corrosion makes sense in theory, I just wonder if it’s a sufficient practical concern to explain AV’s decision to change from brass to SS.

For example I’ve rebuilt somewhere in the neighborhood of 200 regulators over the last 10 years, a mix of hand pumped and compressor filled, the overwhelming majority of which have a brass piston (e.g. Huma, Ninja, etc.), and I do not recall encountering a single example having any galvanic corrosion. Not saying it never happens…I think Scott @Motorhead showed an example some years ago, and it’s possible I’ve run across some subtle surface staining too insignificant to commit to memory but I’m positive I’ve never needed to replace a corroded piston or salvage one with a concentrated effort.

I was thinking maybe the Avenger has some set of factors that makes it particularly susceptible to corroding, but searching for “Avenger regulator corrosion” returned no hits so that made me wonder if the decision to change to SS is related to something else.
 
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nervoustrig said:
Yeah the potential for galvanic corrosion makes sense in theory, I just wonder if it’s a sufficient practical concern to explain AV’s decision to change from brass to SS.

For example I’ve rebuilt somewhere in the neighborhood of 200 regulators over the last 10 years, a mix of hand pumped and compressor filled, the overwhelming majority of which have a brass piston (e.g. Huma, Ninja, etc.), and I do not recall encountering a single example having any galvanic corrosion. Not saying it never happens…I think Scott @Motorhead showed an example some years ago, and it’s possible I’ve run across some subtle surface staining too insignificant to commit to memory but I’m positive I’ve never needed to replace a corroded piston or salvage one with a concentrated effort.

I was thinking maybe the Avenger has some set of factors that makes it particularly susceptible to corroding, but searching for “Avenger regulator corrosion” returned no hits so that made me wonder if the decision to change to SS is related to something else.
Click to expand...
"Galvanic" which creates Pits and eats away on the mated steel/aluminum parts generally also sloughing off a white powdery residue ( really destructive ) I've seen only a couple times with is both instances owners being HAND PUMPERS which indeed can create the most introduced corrosion due to moisture. If humidity of the owners use area is salty it will aggravate the situation further.

Other corrosion I've seen several times has been primarily in BSA and early FX & Logan guns where the use of BRASS & steel & aluminum are used. Had these Tarnished and gooey Green slime gunked up. !!!

Shockingly in all honesty for the amount of PCP's and Regs that go across my work bench the issue of CORROSION is likely less than .5% ( in 10+ years over 1000 guns and many for friends non recorded ) about 5-6 such issues dealt with.
 
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