I have two different ideas for one, I'm just having trouble finding the time to work on it. I'm hoping to have something working by mid to end of December.
Upvote 0
Tuning Air Venturi Avenger upgrade/mod help
- Thread starter Leadslinger01
- Start date
That's sweet! Looks like I found the right spot. I'll just camp right here until you do... And I fully understand the difficulty of finding time. But I definitely want one when you do. I'm newish to PCP rifles. My only other one is a Hatsan Hercules Bully .45 but I really love this Avenger more. So I'm looking to heavily mod it as a field hunter. Something I can take on extended backpacking trips to the wilds.
Upvote 0
One idea is a straight bolt on one but the CFM transfer is slower than a regular avenger plenum. The other would be a kit to fit plus stock modification. This plenum would be more liKe the original ones I make with fast CFM transfer rate.
Upvote 0
Thanks for the help I made my test one and it works great. You are asking a very fair price , it was time consuming to make it. I messed up the first one lol. The one I’m going to use permanently is almost done. I wanted to make it myself because I have access to the proper equipment and skill to do it. Your price is more than fair there isn’t much room for error at the pressures We are running
These at.
Last edited:
Upvote 0
Very nice. I don't know if it's the angle but that looks huge! Did you figure out the volume yet?
Is the main cavity straight through our did you overbore the inside? I do this with my 25cc ones too keep the length down.
Is the main cavity straight through our did you overbore the inside? I do this with my 25cc ones too keep the length down.
Upvote 0
Test one, I might cut the plug end down because it’s really long and rethread it and keep it as a spare. 
Upvote 0
It’s an inch and a quarter shaft stock and yes, I did internally bore it To keep the length down. I have no idea what the CC is on it lol. To the first step it’s 4.25 long.
Upvote 0
The test one is crazy long lol, it was just for testing and to see what happens when you give it as much volume as you can without being longer than my bipod lol. I’ll cut it down and keep it.
Upvote 0
I also made the LDC I made fish bone stile 2 peace baffle system I put a spring in the center between the two so I have an expansion chamber it’s made a big difference. I still have to paint it.
Upvote 0
I use this to figure out volume when designing.
I simply use a syringe and hot water to test actual volume when made and cleaned.
I simply use a syringe and hot water to test actual volume when made and cleaned.
Dude I have to give you props that stuff is very time consuming. I’m making mine because I want the experience of making it, but I would have no problem buying one. My Avenger came under powered so I’m doing this so I can push pellets and slugs at their optimal speeds. At the most I could push the 25.39s at 913 fps now without maxing it out I’m getting 967 fps and I noticed the standard deviation was much lower.
Upvote 0
There's plenty of other restrictions to be taken care of to let these rifles breath better. The barrel port is one of the biggest.
Original .22 port next to 5mm with beveled edges.
Upvote 0
This is very interesting! Any thoughts on opening the barrel port without messing with the transfer port?
Upvote 0
My thoughts are that if there's only one mod you going to do to this rifle, then the barrel port is it.
Upvote 0
While I agree that it helps I actually think the lighter valve spring along with opening up the valve itself helped the most. It was one of the last things I did to my .25 avenger and it had a big impact. I actually put too light of a spring and needed a bit heavier one trimmed down a touch to work better. On my gun I ported the transfer port along with the barrel port and upgraded to the 16cc power plenum ( which is nicely made btw) and it gained roughly 10 FPE which was nice. Now it wasn't until I changed the spring and ported the valve that I gained another 15-20 FPE. The gun has maxed out at 83 FPE using the 43.2 Seneca/run jin pellets. And that there is the catch. This gun is a "pellet gun". With the lighter 34 grain jsb and 20 different slugs it doesn't go much over low 70's FPE. I have found that the barrel is holding back this gun I believe. To really use this new power you have to shoot the pellets a little too fast or hunt for a slug that will work which it seems none of them can rival a JSB pellet due to the barrel design. This is why I have a TJ barrel on order so I can max this gun out with slugs. The TJ barrel "should" increase speeds alot I believe as it is a non choked barrel and will be about 3" longer. I believe I will be able to reach over 85 FPE after that.. hopefully with something other than pellets.
Upvote 0
That's good to know. I was hoping to get to 80+ft/lbs and now I know it's achievable. I don't know how big you went with the valve / poppet but I'll be going 7mm (5.9mm being the max with the OE poppet) with a new peek poppet to match. I'll also be using the 25cc plemum.
I did some 'out of the box' shots last night to see where my new .25 is at and also used the Seneca 43gr pellets. Averaged 53ft/lbs. I can understand slugs holding back as they have way more surface area engaging the rifling = more friction BUT they'll carry more of that energy down range.
Upping the muzzle fpe of slugs will probably require finding a smaller dia slug that engages the rifling less but you'll also have more pressure losses around the slug too.....
Glad you like the plemum
Upvote 0
1cc=1gram of water so you can weigh it empty then weigh it full of water to get the volume.
If you have a lathe or mill there's no need to make it long and skinny. Just jug it out inside with a boring bar. It could be 2inch diameter if you want. Be sure to use 7 series aluminum and put a big radius on your inside corners when you go large diameter. I use a round nose end mill and rotary table for that.
Upvote 0
No need to weight it when you can literally see / measure how much you squirted in with a syringe.
I use 7075 and 1-1/4" for my 25cc plenums. 3/4" for the initial main volume bore then counter bore with a HSS tool I made. Rounded on the back side that comes up towards the plug and pointed on the leading edge. I cut bevels in the front side of the bores to lead into the smaller bores. You do have to be careful on how thin you get the walls.
I do all this in the lathe.
Upvote 0
Yes I went to 5.9mm with the stock poppet. I would be interested to see the results of a custom poppet and 7mm port. Though I wonder if the transfer and barrel port will be able to flow the same. I believe 90 FPE may be achievable however it's possible a heavier hammer may be needed. Just speculation though.That's good to know. I was hoping to get to 80+ft/lbs and now I know it's achievable. I don't know how big you went with the valve / poppet but I'll be going 7mm (5.9mm being the max with the OE poppet) with a new peek poppet to match. I'll also be using the 25cc plemum.
I did some 'out of the box' shots last night to see where my new .25 is at and also used the Seneca 43gr pellets. Averaged 53ft/lbs. I can understand slugs holding back as they have way more surface area engaging the rifling = more friction BUT they'll carry more of that energy down range.
Upping the muzzle fpe of slugs will probably require finding a smaller dia slug that engages the rifling less but you'll also have more pressure losses around the slug too.....
Glad you like the plemum
Upvote 0