Tuning Air Venturi Avenger upgrade/mod help

Hello, first timer here. I'm looking for some help making mods to my Air Venturi Avenger . 25 cal. I'm trying to locate the correct 'light' valve spring to replace the stock one. The tap size for the transfer port 1/4-20 or 1/4-28? Also I was wondering about the pros of adding an 18cc plenum extension "18cc Air Plenum For Air Venturi Avenger. ☆Gauging Interest Only☆ Please Read!" . I was thinking about getting that and a douxsilencers bottle adapter to add a 450cc bottle. I'm hoping to the expand shot count per fill and bump up fps/fpe. Any help is much appreciated. 
 
I've drilled the threads out of the transfer port. I was going to put a threaded and drilled piece of aluminum bar in the but I feel it's just extra work to restrict it again. I've also drilled the barrel port and polished the hammer. 

I've seen someone that polished the contacting surfaces of the washers in the regulator and was getting an average shot spread of just 1 to 2 fps! I'm going to do this soon. 

I am the maker of those plenums (alienairgunsupplies) and the listing has been updated with an accurate, calculated volume of 15.75cc. I've had one customer fit one to a stock .25 and he got a 6fps boost without doing a thing. Others reporting being able to drop the regulator pressure by 400psi and still keep the same pellet speed that they're happy with. 

I can make them bigger, bit it's about how much you're happy with sticking out the bottom of you're rifle. I'm about to make one that's about 27cc for a customer that already purchased a 15cc one. 

I have bought a stock avenger because I don't really have before and after results for myself. I just have to get the time to shoot some groups over the chrony. 

Let me know if I can help you out at all. 
 
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Yeah I want to know this one as well. Am even thinking of putting a plenum on. Though about drilling to open her up but if I do mess up the transfer port I don’t have a tap to redo where the other piece goes in
I do this work if you dont feel confident enough. I drill the transfer port to 1/4" which removes all threads, make a larger (7mm) setscrew fit the lighter spring and enlarge the valve to 5.8mm from 5.4mm to increase air flow. I then put everything back together and pressure test before sending back. $75hr - 2-1/2 hours.

I recently did this work in a .25 action and with a 16cc plenum and just a small amount of testing, it's putting out 76ft/lbs right now. We pretty sure there's more in it but he's having add on regulator issues. It's only putting out 2200psi when it should be 3000psi.
 
Yes, I have lighter springs. Also the 16cc plenum I make seems to add an avarage 6ft/lbs when the barrel and transfer ports are opened up. Has these results given to me by both .25 and .22 owners.
He Reidy, I checked out your ebay site.... looked like the plenums were still listed at 1k which I took to mean you were out of stock. Do you have more in stock? Is ebay the best place to purchase there from you?

Also, just curious what people generally do about the plenum sticking down through the standard stock? I have seen some aftermarket stocks made to accommodate the plenum but do some people cut a hole in the factory stock? I'm just curious what that would look like and how it would function. Thanks
 
Correct, I don't have any in right now. I was going to make more on Sunday morning but I didn't sleep well Sony work time became extra sleep time.

You can purchase direct from me. I can send a PayPal invoice which you can pay with almost bank and credit cards even if you don't have a PayPal account.

You do need to enlarge the degas hole in the stock to accommodate the plenum. I did have a picture with one fitted but cant finding back now?
 
Well how much r ur springs or plenums? See am not really worried about power I can already send slugs 900+fps I want a better shot count when shoots pellets
Plenums are - 10cc - $85, 16cc - $100, 25cc - $175 (I know but they're more of a PIA to make). I can throw a spring in with another purchase.

10cc plenum with spring $95.40 all in, out the door, including extra shipping insurance.
 
Well what would the total be for small plenum and valve spring ?
Well how much r ur springs or plenums? See am not really worried about power I can already send slugs 900+fps I want a better shot count when shoots pellets
Plenum will allow you to turn down your regulator a few hundred psi and still have the same performance, saving you some air.
 
What size do y recommend? Stock avenger but I think I will try opening the barrel port up some to match transfer. And what’s the turn around time? Mite have to sell my back up scope for the funds
I sell more 16cc than any other but the 10cc work too, just now quite as much air (power or efficiency).

I make on Saturday and Sunday mornings. Those I make on Saturday ship that day. So earliest ship date now would be 9-3.

The barrel is the first thing to do and if you do only one tuning mod, that should be it. go as large as you dare. .187" is 85% of caliber but I know people who've gone full caliber and not had issues. You could also go to .187 and slot a little.

I have a bullpup in .22 that I'm going to tune in steps and shoot over the chrono each step to show the changes.
 
Let's you get more air through without going wider than the pellet head.
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