GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Rohmpm on March 28, 2019, 11:26:13 PM
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Some of you are aware of the plenum I've been working on for the Liberty. I received my new, unmodified gun, I am starting from square one.
The gun is a new 22 Liberty with absolutely no modifications testing with four pellets.
Filled the gun to 3k. Average of five shots each, these numbers are specific to this gun, all shots single loaded.
21.14 Barracuda match 744 fps 25.9 ft lbs
28.5 Eunjin 637 fps 25.7 ft lbs
15.89 JSB 860 fps 26.1 ft lbs
18.13 JSB 817 fps 26.9 ft lbs
Next I removed the factory plenum and replaced it with the one I have pictured previously,
No other changes. The guage I have on the plenum indicated 21-2200 psi. I would assume that the factory plenum would have been the same. Again, average of five shots each.
21.14 Barracuda match 784 fps 28.8 ft lbs
28.5 Eunjin 679 fps 29.2 ft lbs
15.89 JSB 905 fps 28.9 ft lbs
18.13 JSB 860 fps 29.8 ft lbs
With no other changes on a bone stock gun, the larger plenum was about three ft lbs to the plus on all four pellets.
Tomorrow I will enlarge all ports to .187 and test again. I reposted the prior pics of my modified gun with the large plenum.
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Will you have them available. That along with a barrel port drilling could be awesome
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Subscribed. I love watching a plan come together.
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Will you have them available. That along with a barrel port drilling could be awesome
I plan on offering them when testing is complete. Looks like two versions, one that will fit unseen within a modified stock, very simple in synthetic. I also bought a wood stock gun to see what is necessary for fitment, definitely not as simple as the synthetic version. The other will be larger in volume, requiring more modification and protruding slightly from the bottom of the stock, for those seeking the most power.
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Billy,
Great idea to start a new thread regarding the plenum since the original one seemed to be going in all directions. Looking forward to following your work and testing. Once you have the plenums available for sale, will you start some type of list to sign up and purchase?
Thanks again for taking the time to do this for us, Tom
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I think Billy might have had the list constructed already. i just know i am supposed to be one of the first on the list. ;D...cnc plenum, who doesnt want them?
good work Billy. cant wait to see the tesults with all the ports opened to 3/16 and 7/32 if you are up to it?
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Looking amazing Billy!!!!
What sort of increase are you looking at with the larger Plenum?
I am definitely keen on a larger one, now hurry up ;) as I want to build myself a new stock which will be designed with your plenum in specifically.
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+1 on the plenum 😎👍🏾
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Can you post a pic of both plenum side by side. I guess with a wood stock you can't make it too wide or it will sacrifice the strength of the stock at the plenum.
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+1 got a synthetic parts gun just to add you new and improved plenum. MORE POWER arrrrrrr.
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Will you have them available. That along with a barrel port drilling could be awesome
I plan on offering them when testing is complete. Looks like two versions, one that will fit unseen within a modified stock, very simple in synthetic. I also bought a wood stock gun to see what is necessary for fitment, definitely not as simple as the synthetic version. The other will be larger in volume, requiring more modification and protruding slightly from the bottom of the stock, for those seeking the most power.
Looking forward to what you come up with on the wood stock. :)
I agree, from what I see, it will be a bit tricky with the wood stock (narrower) and being right at the balance point of the rifle. Protruding items, would be an annoyance. If it was at least flush with the gauge removed, and plug inserted, would be great. It would be nice to have the gauge flush to the bottom, given the external reg adjuster, but don't know if that compromises too much on the plenum size. That won't satisfy the power users though. :D
FWIW: Your stock power numbers look right in the range of what I have observed.
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The stocks are so big and bulky in that area that a protruding plenum may not be that big of a deal. I think the gauge on the bottom is a great idea. You can monitor your reg pressure and creep if you have any.
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Am I wrong on this but with increased plenum size we can decrease our reg setpoints without losing power ( Maybe even gain power) and get an awesome number of shots without ridiculous (hand pump) fill pressures.
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Glad to see this in a new thread. I will be ordering one of these.
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Subscribed, you guys are great! I'm so lucky to be a member of the Liberty Club ;)
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Am I wrong on this but with increased plenum size we can decrease our reg setpoints without losing power ( Maybe even gain power) and get an awesome number of shots without ridiculous (hand pump) fill pressures.
Yes, and that is my primary motivation to wanting a bigger plenum. :) While it is nice to have the ability to fill to relative high fill pressures, I'd prefer to get more shots from a 3500 fill.
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Am I wrong on this but with increased plenum size we can decrease our reg setpoints without losing power ( Maybe even gain power) and get an awesome number of shots without ridiculous (hand pump) fill pressures.
Yes, and that is my primary motivation to wanting a bigger plenum. :) While it is nice not to have the ability to fill to relative high fill pressures, I'd prefer to get more shots from a 3500 fill.
The only thing that I really miss on the Liberty is the ability to tune the HST easily...I'm too spoiled with my Taipan...
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Put me down for a wood stock plenum ( it can protrude ) Billy...
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Am I wrong on this but with increased plenum size we can decrease our reg setpoints without losing power ( Maybe even gain power) and get an awesome number of shots without ridiculous (hand pump) fill pressures.
I have already demonstrated that with a gun that was already modified so the results could have been inconclusive. Exactly why Iv am startind anew with a bone stock gun to document each change.
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Thanks Billy I really appreciate the effort
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Am I wrong on this but with increased plenum size we can decrease our reg setpoints without losing power ( Maybe even gain power) and get an awesome number of shots without ridiculous (hand pump) fill pressures.
I have already demonstrated that with a gun that was already modified so the results could have been inconclusive. Exactly why I am startind anew with a bone stock gun to document each change.
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Looks like there will not be shortage of Liberty owners whom are willing to take their's to the next level of performance.
Sounds very promising.
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Count me in, looking forward to this one.
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Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.
Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.
Does my logic sound ok?
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Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.
Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.
Does my logic sound ok?
Wow, impressive. It is beyond my experience to predict what kind of power a fully modified gun will produce. I've done a lot of cylinder head development for motorcycles, drag racing, top speed, road racing. At that level of performance, the farther we got, the more diminishing the return.
My initial goal was more shots at equal to factory power levels. I am certain that there are some who will seek the extremes at both shot count and power. It will be very interesting to follow.
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Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.
Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.
Does my logic sound ok?
the key word is larger plenum and mods. i have no doubt it will be 60-65 fpe if you go to .25 caliber. hitting 65fpe will be hard on .22 and if possible its for limited shot counts at closer to 3000psi with the current barrel length.
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Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.
Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.
Does my logic sound ok?
the key word is larger plenum and mods. i have no doubt it will be 60-65 fpe if you go to .25 caliber. hitting 65fpe will be hard on .22 and if possible its for limited shot counts at closer to 3000psi with the current barrel length.
There you are from someone who knows.
I'm busy on the dyno today but hopefully I'll get done in time to work with the plenum this afternoon.
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Oh i dont know it at all. i am just good at guessing... 8) not really. i just compare to the gaunlet with 25cc in 25 cal making 70fpe and in 22 cal making 50fpe...same set up and cothran valve with bigger ports on 2000psi.
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darn USPS misread the zip on my package to Duy and it is sitting in PA! I was tracking it and I'm in Illinois and Duy is in Texas !! They misread the first # .... Hopefully it will get there Monday or Tuesday for his magic touch..
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darn USPS misread the zip on my package to Duy and it is sitting in PA! I was tracking it and I'm in Illinois and Duy is in Texas !! They misread the first # .... Hopefully it will get there Monday or Tuesday for his magic touch..
They only do this when they know you are anxiously waiting for it ;D
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The furthest I want to push my Liberty right now would be to open the barrel port, shim the hammer spring and turn the reg up but for now I'm happy with the way it is. Tomorrow I think I'll try it in woods but I'll have to be using my single shot tray because the mags haven't come yet, should be here Tuesday or Wednesday :D
I did fill it up to 4K after my last shot string from 250bar, it's the highest I've ever filled a pcp to. It didn't seem to phase the gauge on my SCBA too awful much in doing so but it is one of the 87cf ones.
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Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.
Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.
Does my logic sound ok?
Steven I haven't tried a slug in mine yet but I'm sure the Liberty would shooting them well with the non choked barrel and slow twist rate for the 30 grain BBT's They shot really great from my SPAM16 which is non choked and 1 in 20" twist barrel before I tamed it back down for the Magnum Hunter's that I dearly enjoy hunting with.
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The furthest I want to push my Liberty right now would be to open the barrel port, shim the hammer spring and turn the reg up but for now I'm happy with the way it is. Tomorrow I think I'll try it in woods but I'll have to be using my single shot tray because the mags haven't come yet, should be here Tuesday or Wednesday :D
I did fill it up to 4K after my last shot string from 250bar, it's the highest I've ever filled a pcp to. It didn't seem to phase the gauge on my SCBA too awful much in doing so but it is one of the 87cf ones.
I did get a little nervous in filling my Liberty to 3500 PSI and for now I may leave it at that. :o
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Bob I'm sure that with a titanium airtube they're plenty strong, nothing is leaking at all on mine that I can notice. The next time I take the barrel off I'm going to replace the o rings on it because I noticed one had sheered just a tad. I might even have the right ones for it because quite some time ago I ordered some thin metrics in a kit from "The O Rings Store" and there's a good assortment of probably just what I need. They're 70duro which I figure should be good enough on the barrel.
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Back when I first got the Liberty, I thought it was being constrained by the small plenum, more than it actually is. I looked on AliExpress at those small air/water filters for PCP pumps. I assumed the plenum was a M10X1 thread, but never verified. I found one that was about the same external size, but probably less internal. Even ones that were 30mm OD X 80mm length, didn't seem to have a good size internal volume, and would be a problem with the wood stock. Just adding a gauge to the oem plenum will be right at the bottom of the wood stock.
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I've always filled my Liberty's to 4300psi. Never had a problem. If the manufacturer rates the gun for that pressure, I'm filling to it. If it doesn't hold, the gun goes back.
Months of daily use, and several thousand pellets later, still no issues.
And it's obvious that the manufacturer has built in a large margin of safety. The gun has a 6000psi burst disk, telling me that the tube and components are rated to handle way more than the 4300psi max listed fill pressure.
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I've always filled my Liberty's to 4300psi. Never had a problem. If the manufacturer rates the gun for that pressure, I'm filling to it. If it doesn't hold, the gun goes back.
Months of daily use, and several thousand pellets later, still no issues.
And it's obvious that the manufacturer has built in a large margin of safety. The gun has a 6000psi burst disk, telling me that the tube and components are rated to handle way more than the 4300psi max listed fill pressure.
I think the weak link is, if the reg fails and 4300psi is throughout, the poppet may fail. It will certainly valve lock.
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I am sure the manufacturers done their work before and after publishing their recommended max working pressure. What we don’t know is at what safety factor. I would love to know all that detail and the rating of the material they used. I am sure someone would know and chime in soon
If it were me I would put in a 5k burst disk instead so that the tube would not reach the “point of no return” . I am no expert but if the 4300psi was calculated on the yield strength. Which means if someone goes beyond that pressure, the material is approaching point of yield (depends on safe factor 2:5 or 3:1 or 3:5?) ...you are stepping into the yellow and soon reach the red zone. Yes it won’t burst at 6k but...how many fill cycles remain NOW? Yes it can handle more than 4300 before burst but is it compromised beyond 4300psi? That’s why they put the word “max” fill pressure on there right?
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It probably wouldn't hurt to mike the diameter of the air tube when new and check once a year or so for growth. Regards, Tom
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I post it as I see it.
I dissasembled the gun and drilled all ports to 3/16 with a new carbide drill bit.
Upon reassembly the regulator now reads about 1800 psi versus 21-2200 psi in prior test as received. Puzzling as I made no adjustments to the regulator.
So, I ran some pellets with both plenums. First number is the large plenum, second is original at 1800psi, 3/16 passages from valve to barrel.
large. original
Eunjin 666. 639
JSB 18.13. 863. 827
JSB 15.89. 896. 872
compare this to the original test, all factory at 21-2200psi, no porting.
large. original
Eunjin. 679. 637
JSB 18.13. 860. 817
JSB 15.89. 905. 860
what this really shows is what larger ports do at reduced regulator output. It shows that the plenums produce near the same results with 300 less psi when ported.
any input on why the regulator setpoint dropped upon dissasembly and reassembly.
Tomorrow I will raise the regulator output toapproximately where it was at the beginning.
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The original plenum and the plenum I am currently testing.
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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.
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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
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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.
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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
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WOW Duy that plenum looks huge. Very nice
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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.
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Mine came with three.
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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.
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Sorry I meant Billy
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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.
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Looks like the wood stock version would have to be smaller diameter and longer... That would be O.K. with me and Duy..
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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.
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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.
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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?
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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.
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Hey Rohmpm;
How's the experimenting going on your side?
I'm super keen!!!
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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?
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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.
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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
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yah Billy is on vacation. i made a crude 19cc plenum but broke a tool so it also on halt.
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This is the next thing to buy for my Liberty.
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Sounds like a fun add on.
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I am currently working on the crude plenum...Hopefully I can finish it end of this week, cause week after that I am going vacation "again" haha. California I come!
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From the looks of things, the larger plenum and a little extra air port size may be the key to higher velocity while keeping the shot count up .... I'm watching !
wll
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I am currently working on the crude plenum...Hopefully I can finish it end of this week, cause week after that I am going vacation "again" haha. California I come!
https://www.youtube.com/watch?v=7I0vkKy504U (https://www.youtube.com/watch?v=7I0vkKy504U)
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So what's the word on the bigger plenum? I'd love one with a gauge on the bottom to know for sure what the reg is doing.
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I heard a pin drop after you asked that question.
The theory sounds solid.
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Billy was already testing one and getting higher vel with the reg set lower than stock aka original.
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did he post the results here?
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Post 39 on the first page.
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So what's the word on the bigger plenum? I'd love one with a gauge on the bottom to know for sure what the reg is doing.
I'm thinking when I get some time to do an extension rather than a replacement. The trepanning of the 16mm O ring on the face seal is a bit of a bother, in comparison to the OD of the plug end.
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thats not a bad idea, and extension. it maybe just a few cc added going that route but will be much easier to make.
once i get Billy's plenum, i think my rifle will wake up and hopefully i can hit 60fpe with all my mods and my valve. then going .25 cal will even get it close to 70fpe range. :o i am still being conservative.
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thats not a bad idea, and extension. it maybe just a few cc added going that route but will be much easier to make.
once i get Billy's plenum, i think my rifle will wake up and hopefully i can hit 60fpe with all my mods and my valve. then going .25 cal will even get it close to 70fpe range. :o i am still being conservative.
That's my thinking, it will allow me to test velocity "out of stock". If it does prove out to be a velocity throttle, it would be simple enough to port my wood stock. Like the 10/22 the flush mag is comfortable but its still doable as a shooter with an extension.
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After the 29 fps gain with the modest plenum extension it became clear stumbling in the dark on the regulator pressure isn't helping.. Used one of the extension blanks to make a Gauge rig.
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What thread is the part of the plenum that threads into the receiver?
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What thread is the part of the plenum that threads into the receiver?
10mm 1.25 pitch
Back of Plenum
16mm 1.25 pitch
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Thank you!
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After the Fx plenum discussion I figured it might be time to bring this backup. Did anyone ever figure out the maximum FPE and shot count with an extended plenum? Anyone have an extended volume version on a wood stock liberty?
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https://www.gatewaytoairguns.org/GTA/index.php?topic=160469.180 (https://www.gatewaytoairguns.org/GTA/index.php?topic=160469.180)
go to the last page, some limited testing infor on the larger plenum Billy sent me