Air Venturi Avenger Bullpup Plenum?

[EmptyTin_Tim]

Just wondering if anyone got one of those Doux or c88 machining type plenums to fit on an original Bullpup or the new Gen 2 Avenger Bullpup (not avenge x).

It's my understanding that the trigger linkages run underneath so the plenum sticking out would not work. Is this true? If so, Is there a work around?

I have an extra doux plenum and if I got a bullpup avenger I'd wanna install it. That's why I'm asking.

 

[Garuda]

I have both types on my avenger bullpup. if you get the external type make sure it goes on the low pressure side (regulated air side) and not the high pressure side. For the type that screws into the internal plenum, you have to get a trigger bar that is modified to work around the additional plenum. I got my off of eBay from air hunter pro. I'm not sure if you can get them anymore.

 

[EmptyTin_Tim]

I have both types on my avenger bullpup. if you get the external type make sure it goes on the low pressure side (regulated air side) and not the high pressure side. For the type that screws into the internal plenum, you have to get a trigger bar that is modified to work around the additional plenum. I got my off of eBay from air hunter pro. I'm not sure if you can get them anymore.View attachment 521221

WOAH! I had to zoom in to see all your modifications. You've done quite a lot!! I think you tripled the plenum space by having both kinds on there. Bet you could sling some heavy lead no issues. I just installed the long tube I removed from my regular, bottled Avenger and replaced the short tube on my bullpup so now I have 280cc of air for only like 7 oz more weight.

A few months ago I actually contacted the seller of the plenum you put on the reg side and he tried on his avenger (not x) and said it didn't clock correctly. How did you get that to go straight down? O ring? Or you luck out. Id prefer it to go parallel with the barrel but that'd work too I guess. Since my cocking lever is forward on the bullpup II I want to avoid a plenum in the way.

Also, I found the ebay seller you mentioned for the transfer bar and inquired after not seeing one for sale. Will see what he says. I already have a doux plenum laying around so if this guy has a trigger bar I may go that route unless he says it's like $$$ and the side mounted plenum is cheaper. But with the side one don't you have to get some special gauge? Like you couldn't just use the stock one i mean? I wouldn't necessarily wanna spend the bucks on a digital one if I didn't have to. Would think the threads would be the same and can just re use the stock manometer?

 

[Garuda]

There are a couple of ways to get it clocked in the right position. I bought a pack of dowdy seals from amazon and went through the batch to get the best one. The is another method where you use a space and oring. You will also need to mod the stock if you want it in the same position. Alternative is straight mount to the right side vs. a 90 degree bend. The external is more than plenty of plenum without having to worry about replacing the trigger bar.

 

[Garuda]

The gauge on the side is 1/8 BSP vs M8. They are less than 10 buck off eBay but takes a minute since it is shipped from China. I have an extra if you decide to do that I can throw in an envelope and send to you.

 

[EmptyTin_Tim]

There are a couple of ways to get it clocked in the right position. I bought a pack of dowdy seals from amazon and went through the batch to get the best one. The is another method where you use a space and oring. You will also need to mod the stock if you want it in the same position. Alternative is straight mount to the right side vs. a 90 degree bend. The external is more than plenty of plenum without having to worry about replacing the trigger bar.

I have a thing of dowdy seals off Amazon too! Bet I could find one that'd fit. The seller said using a washer is possible but said the actual used threads would be shorter since some are taken up by the washer thickness. But it seems yours works fine! Once pressurized I'm sure that helps keep things together. I wouldn't want to modify my stock in a way that's irreversible. I promised myself I'd only do things that can be un done with the bullpup since I went ALL out on my regular Avenger. So I'd wanna make it parallel to the barrel. Sounds like external is the way to go.

However, I went on the seller ebay page and couldn't find the external plenum for sale now...

Thank you for the thread sizes , now I understand why it wouldn't work. I'm confused as to why the manufacturer wouldn't just make the external plenum function with the oem manometer. Everyone already has that gauge.

I'll have to see if the external plenum goes for sale again. Appreciate the offer on the gauge!!

 

[EmptyTin_Tim]

The gauge on the side is 1/8 BSP vs M8. They are less than 10 buck off eBay but takes a minute since it is shipped from China. I have an extra if you decide to do that I can throw in an envelope and send to you.

Okay got a message back. External plenum seller says he is making more right now and should have some in a few weeks. Also they'll come with shims to clock correctly. So I guess I'll have to see if the shims will work or I'll have to use a dowdy since it is really designed for the avenge x but happens to use same threads as avenger.

What cal is your bullpup? What kind of fpe at what settings you get with those two plenums on yours. Bet you can drop the reg psi very low and still maintain good #'s.

Mine is .25 and I haven't tested enough but know a bigger plenum can help lower reg pressure for same fps so I can get more shots/fill. But I'll probably find the higher fpe in this one since I have a bottled .22 normal Avenger that can do like 60/fill at 35 fpe or so.

 

[Garuda]

My BP is in .25. I didn't notice much difference with two plenums vs just one. I did notice the refresh pressure is slower with two plenums especially when they are separated. The digital gauges are awesome at showing the precise real time changes in pressure. I use 34 gr pellets for my baseline and I can push them up to 1000 fps. So that puts the fpe around 70 or so. 80 fpe is about the highest I have gotten it, but didn't push it too much past that to keep it backyard friendly. I did some other internal mods like opening up the valve opening to 6mm and replaced the valve stem with one from AEA. Stem was thinner and poppet was made of PEEK. I had to trim the stem to make it match the length of the original and change the oring in the seat with one that had a smaller opening to fit the new stem. After that mod I was getting plenty of air. Probably too much since the noise level went way up with little change in velocity. I reverted back to the stock spring and am getting 950fps with very little noise. With 35gr Zan slugs, averaging 900fps and 1/4 inch groups at 30 yds. Finding the right balance with reg pressure, Hammer spring strength/preload is tricky but doable. I think I am pretty close to maxing out the mechanical capabilities on the avenger. BL getting to 70fpe fairly easy, especially with bolt on or DIY mods. Getting up to 90-100fpe much harder and requires more advanced tools and skills.

 

[EmptyTin_Tim]

My BP is in .25. I didn't notice much difference with two plenums vs just one. I did notice the refresh pressure is slower with two plenums especially when they are separated. The digital gauges are awesome at showing the precise real time changes in pressure. I use 34 gr pellets for my baseline and I can push them up to 1000 fps. So that puts the fpe around 70 or so. 80 fpe is about the highest I have gotten it, but didn't push it too much past that to keep it backyard friendly. I did some other internal mods like opening up the valve opening to 6mm and replaced the valve stem with one from AEA. Stem was thinner and poppet was made of PEEK. I had to trim the stem to make it match the length of the original and change the oring in the seat with one that had a smaller opening to fit the new stem. After that mod I was getting plenty of air. Probably too much since the noise level went way up with little change in velocity. I reverted back to the stock spring and am getting 950fps with very little noise. With 35gr Zan slugs, averaging 900fps and 1/4 inch groups at 30 yds. Finding the right balance with reg pressure, Hammer spring strength/preload is tricky but doable. I think I am pretty close to maxing out the mechanical capabilities on the avenger. BL getting to 70fpe fairly easy, especially with bolt on or DIY mods. Getting up to 90-100fpe much harder and requires more advanced tools and skills.

That's amazing! I should have just gotten the .25 in the first place. I wanted .22 for cost of pellet but I did almost all mods you mentioned (have not drilled valve but did make barrel port to 5 or 5.5mm). I actually had an issue with the light valve spring because it isn't ground down flat so the coil got caught a few times on the "ears" of the oem poppet and made my Avenger "go auto" cause it wouldn't close and would go brrrt occasionally. I put oem back in since it is ground flat. But had heavy hammer spring in there and all that, was getting 50 fpe with 25.39 gr and could also sling 17.5 gr slug at like 1020 fps lol

But for the bullpup I promised myself no crazy mods if it screws on ill do it but I don't wanna mess with it otherwise since I kept doing every mod to regular Avenger. Have 2 regs and even polished both regulator washers on that one. I just wanna shoot and not worry about a mod messing it up.

That's interesting the plenum refresh rate is slow , and especially when you have both. If your reg is set high I can see why. Slightly bigger volume at little higher pressure on fill side and only little smaller plenum volume at not much psi difference, it isn't much to balance out quickly.

I've a friend with a Maverick and he gets like 50 shots / fill at 925 fps with those 34 gr pellets. Not sure I'll max mine out to match that because I am not bottle modding mine but it'll be interesting to see max fpe balance with more shots / fill since i have that 2nd long tube on there now. I know I'd definitely need a better back stop if I had a 80 fpe slinger like yours!

I'd like to make my bullpup a slug gun. Did you try NSA slugs in yours before the ZAN? I've read the 29 gr are best for this barrel but I only had them going at like 875 fps and they definitely were not stable at that speed. The 26.8 gr were at 920 or so and they weren't stable there either. Better. But still shotgun at 75 yards.

 

[Garuda]

I tried NSA but couldn’t get them to shoot. The diameter was .249. Reluctant to order another batch in .250 when the Zan 35 are shooting really well out of them. The best accuracy is when I push them right around 900 fps. If I watch the digital gauge on the plenum and wait for it to reset to the same pressure the slugs are one ragged hole. The best accuracy mod in my opinion was building up the barrel with carbon fiber tubes. I was able to trap the Donny fl adapter inline with the barrel as I was building it up and cut a section of the original shroud to give the adapter something to screw into. After that the barrel shot great.