Liberty plenum

[Rohmpm]

The original plenum and the plenum I am currently testing.

[darkcharisma]

since you havent adjusted the regulator wheel. my guess is when assembling, try screwing the regulator into the pressure tube block very snug before screwing into the receiver. any amount of play even 1/12 of a turn can effect the output.

[Rohmpm]

since you havent adjusted the regulator wheel. my guess is when assembling, try screwing the regulator into the pressure tube block very snug before screwing into the receiver. any amount of play even 1/12 of a turn can effect the output.

I made sure I did exactly that or the or the tiny oring on the end will leak. Have you noted that the regulator "pressure relief valve stem" appears to be retained by the poppet spring.  Trying to figure that thing out.
One more thing, the airtube was  1/4 turn loose. Perhaps it was returned as a leaker at 4300, but in testing I'm only filling to 3000.I

[Rohmpm]

Another issue? Did your guns come with a hammer spring spacer. This gun showed absolutely no signs of ever being disassembled but it had five .020 washers on the hammer spring as pictured.

[darkcharisma]

Another issue? Did your guns come with a hammer spring spacer. This gun showed absolutely no signs of ever being disassembled but it had five .020 washers on the hammer spring as pictured.

I wouldn't call it an issue, maybe oem has to shim for a production targeted fps, sometimes its faster to shim then to degas and adjust the reg. mine has 3

[dpittman]

WOW Duy that plenum looks huge. Very nice

[FuzzyGrub]

Hard to tell for sure, from the pictures, but looks like two different washers.  That would lead me to believe it was an owner that installed the extra two.

[superchikn]

Mine came with three.

[darkcharisma]

since you havent adjusted the regulator wheel. my guess is when assembling, try screwing the regulator into the pressure tube block very snug before screwing into the receiver. any amount of play even 1/12 of a turn can effect the output.

I made sure I did exactly that or the or the tiny oring on the end will leak. Have you noted that the regulator "pressure relief valve stem" appears to be retained by the poppet spring.  Trying to figure that thing out.
One more thing, the airtube was  1/4 turn loose. Perhaps it was returned as a leaker at 4300, but in testing I'm only filling to 3000.I

WOW Duy that plenum looks huge. Very nice

thats Billys plenum. if i make my own it would be larger and uglier...the ugly part is why i try to buy Billys

Billy, yes i noted the valve spring pushes against the regulator. if turn brass wheel clockwise will stiffen the spring too ever so slightly.

[dpittman]

Sorry I meant Billy

[Lastdog]

Billy, leaving the country for a few months. Take me off the list. Will be following and will contact when I get back. Got to have one.

[cosmic]

Looks like the wood stock version would have to be smaller diameter and longer... That would be O.K. with me and Duy..

[Rohmpm]

I've been very busy but spent time with the plenum yesterday, adding to the port work which I will report on when I'm satisfied that it is reliable.

The regs definitely creep, sometimes up to 500 psi, especially when filling. You can watch the pressure drop to the set point over a few shots and remain fairly consistent, sometimes creeping 100+ when sitting for a bit so I disregard the first few shots.

 Also I have noted changes in the set point just disassembling the gun and reassembling.
That has made it difficult to compare other changes such as porting before and after. 
Yesterday I chronoed a few 21.14 Barracuda match at 1400 psi with .060 added to the hammer spring. Averaged 858, with only 1400 psi. Looks promising for my original intent of lowering the set point for an extended shot count. 

Next week I'll lean on it a bit for power and call it done.

[Rohmpm]

Step by slow step, 1900/2000psi in the plenum. .080 additional on the hammer spring for a total stack of .140.

Barracuda 21.14 match at 958 for 43 ftlbs.

out of Eujins, "dang". So, I stacked a 15.89 JSB and the 21.14 Barracuda. No shroud on the barrel.
I'm not sure how this would relate to a single pellet weighing in at 37.03  but it delivered 771 fps for 48.9 ft lbs.
Tomorrow I'll up the reg to 2500 but I really feel we are barrel length limited compared to a Gauntlet and might just waste air.

[darkcharisma]

Billy. what is your current valve throat and exhaust with you current results?
what about the valve lift? are you using the stock valve stem?

[Rohmpm]

Reused the stock stem. Ground it down to reduce the stem diameter. Bored(drilled) the valve body .030 larger. Made a peek valve that just fits the sealing ring and burnished it in with rubbing compound because I had a slight leak. Seals perfectly now.
All ports are still 3/16. Considering enlargeging them slightly.

[Letum]

Hey Rohmpm;

How's the experimenting going on your side?

I'm super keen!!!

[kzz1kaw]

I've been very busy but spent time with the plenum yesterday, adding to the port work which I will report on when I'm satisfied that it is reliable.

The regs definitely creep, sometimes up to 500 psi, especially when filling. You can watch the pressure drop to the set point over a few shots and remain fairly consistent, sometimes creeping 100+ when sitting for a bit so I disregard the first few shots.

 Also I have noted changes in the set point just disassembling the gun and reassembling.
That has made it difficult to compare other changes such as porting before and after.
Yesterday I chronoed a few 21.14 Barracuda match at 1400 psi with .060 added to the hammer spring. Averaged 858, with only 1400 psi. Looks promising for my original intent of lowering the set point for an extended shot count.

Next week I'll lean on it a bit for power and call it done.

Would changing out the Belleville washers to a better quality ones from McMaster help with the reg creep?

[USAFANG6799]

I've been very busy but spent time with the plenum yesterday, adding to the port work which I will report on when I'm satisfied that it is reliable.

The regs definitely creep, sometimes up to 500 psi, especially when filling. You can watch the pressure drop to the set point over a few shots and remain fairly consistent, sometimes creeping 100+ when sitting for a bit so I disregard the first few shots.

 Also I have noted changes in the set point just disassembling the gun and reassembling.
That has made it difficult to compare other changes such as porting before and after.
Yesterday I chronoed a few 21.14 Barracuda match at 1400 psi with .060 added to the hammer spring. Averaged 858, with only 1400 psi. Looks promising for my original intent of lowering the set point for an extended shot count.

Next week I'll lean on it a bit for power and call it done.

Would changing out the Belleville washers to a better quality ones from McMaster help with the reg creep?

Looks like this post is dead or in a coma.

[Orion]

Looks like this post is dead or in a coma.

LOL, I can imagine the good work requires some time... I'm listening here but I understand if it goes slow....

Let me share something now. Before I changed the reg pressure I was having Reg Creep but not as big as the creep I'm having now after the increased reg pressure, I'll play with this new setting but I'm thinking going back to stock pressure once I decide what will be the pellet for this gun. CPHP are just going too fast for my taste at almost 1000fps