Air Venturi Avenger Bullpup power tune drifting down over time

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DFP771

Member
Jul 16, 2022
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Aromas, CA USA
I purchased a Avenger Bullpup 22 cal a couple weeks ago. I have a chrony and I tuned the Avenger for max power shooting ZAN 23g .218 slugs at about 891 ft/sec. My reg is at 2900 and the hammer spring at 1/4 turn from max clockwise.
My muzzle energy has been drifting down w/o any adjustments. Do I need to replace the o-rings in the breech of the gun? They look fine.
The same slugs are at about 865 ft/ sec now.
 
Fill the gun up and see what your max speed is with your hammer spring. Back it off 25fps with the spring then refill the gun and keep tabs on your speed. You could have just been dealing with your hammer spring finally settling in. If you were at 890fps and your gun is now 865, you’re right where your gun should be happy. I guess you already know what speed your gun is capable of so maybe just skip my first two sentences. Just monitor it for a while. You definitely don’t want to be back at 890fps. You’re wasting too much air being right on top of your plateau at 890fps. Slugs don’t like dirty air.
 
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It could have just been the spring getting worked over until it settled in. You didn’t mention how accurate the gun is at 2,900psi on the reg. Accuracy could get better or worse when you drop to 2,700psi. If your gun is capable of 890fps at 2,900, it might only be capable of let’s say 860fps max at 2,700. Then you have to back that 860fps down to 830fps to balance out the gun. That might be too slow for your needs. By todays standards 2,900psi or even 2,700 is an insanely high reg set point. That’s like 180+ bar. What it is doing in your favor for slugs is closing the valve poppet faster. You just have to decide if it’s worth it. It might be accuracy wise but your poppet might be in there dropping F bombs every time you pull the trigger.
 
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OK. I have the reg @ 2700, 5.5 HS, I get 33 shots @ 885 ft/sec with a 20.2g slug (NSA .218), SD=3, range of 12 ft/sec. I will check this energy (35 ft lbs) in a week and see if it stays there. I have to check my accuracy @ 25,50, 75 yds and see if this gun will do the job of taking care of the ground squirrels on my property. And see if the 23g ZAN slugs are too heavy for it.
 
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DFP771 said:
OK. I have the reg @ 2700, 5.5 HS, I get 33 shots @ 885 ft/sec with a 20.2g slug (NSA .218), SD=3, range of 12 ft/sec. I will check this energy (35 ft lbs) in a week and see if it stays there. I have to check my accuracy @ 25,50, 75 yds and see if this gun will do the job of taking care of the ground squirrels on my property. And see if the 23g ZAN slugs are too heavy for it.
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Did you ever got a chance to test it at 50 and 100 with the 20.2 ??
 
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