Dreamline Reg pressure question.

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MACTEN

MACTEN

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Nov 18, 2020
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I have the .25 cylinder version, and am finding i'm getting 48 shots at 50 fpe average. My reg pressure is set to what I figured was too low at 120 bar. I have a tuning hammer spring I'm using (only 5 turns in) and have the barrel port turned to dual port instead of the pellet hole. When I look up what most folks are setting the reg at I think I'm finding 140-150 bar. Anyone else getting these numbers and shot amounts at 120 or so with a dreamline cylinder version?
 
qball said:
120 is plenty for pellets but not quite enough for slugs and definitely not enough for heavier slugs but Dreamline can’t push really heavy slugs to begin with.


If it shoots well or if ain’t broken then don’t fix it. What are you trying to do?
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What I'm putting through the chrono is .30 grain slugs. I have no idea how they shoot but didn't want to waste my 33.95's...
 
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I can't comment on the regulator setpoint but we can calculate the efficiency to get a sense of how the gun is doing. The cylinder version of the Dreamline is rated at 220cc with a 230 bar fill. 48 shots at 50fpe down to 120 bar represents an efficiency of 1.62fpe/ci which is outstanding.

How is the accuracy? If it's good, don't change a thing.
 
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nervoustrig said:
I can't comment on the regulator setpoint but we can calculate the efficiency to get a sense of how the gun is doing. The cylinder version of the Dreamline is rated at 220cc with a 230 bar fill. 48 shots at 50fpe down to 120 bar represents an efficiency of 1.62fpe/ci which is outstanding.

How is the accuracy? If it's good, don't change a thing.
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I haven't shot it on the range yet. I know the .25 has a larger cylinder than the .177 and .22.. (290cc v 220cc) So not as good as your calculation unfortunately.
 
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Got it. A 290cc cylinder works out to 1.23fpe/ci which is a little low by modern standards. That could be an indication of
  1. Too much hammer spring tension (HST), meaning overdwelling the valve and wasting air (operating too close to the velocity plateau)
    - or -
  2. Regulator setpoint too low for the desired power level
    - or -
  3. A little bit of both since they are inextricably related
The usual starting point for any regulated gun is getting the HST dialed to the velocity knee (somewhere around 95 - 97% of max velocity). This state of tune is where it will have the best balance of air usage and consistency. And that's still good advice for your situation, except it needs to be done with the JSB 33.9gr if that's the pellet you intend to use. Or at least something very similar to it like a diabolo pellet of similar weight if you're trying to save your JSBs. You mentioned using a 30gr slug for the chronograph work so far, and a slug will usually respond quite differently because of its vastly higher bore friction.
 
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nervoustrig said:
Got it. A 290cc cylinder works out to 1.23fpe/ci which is a little low by modern standards. That could be an indication of
  1. Too much hammer spring tension (HST), meaning overdwelling the valve and wasting air (operating too close to the velocity plateau)
    - or -
  2. Regulator setpoint too low for the desired power level
    - or -
  3. A little bit of both since they are inextricably related
The usual starting point for any regulated gun is getting the HST dialed to the velocity knee (somewhere around 95 - 97% of max velocity). This state of tune is where it will have the best balance of air usage and consistency. And that's still good advice for your situation, except it needs to be done with the JSB 33.9gr if that's the pellet you intend to use. Or at least something very similar to it like a diabolo pellet of similar weight if you're trying to save your JSBs. You mentioned using a 30gr slug for the chronograph work so far, and a slug will usually respond quite differently because of its vastly higher bore friction.
Click to expand...
This is at 95% of max velocity at 120 bar with the tuning hammer spring. I will set the reg up to 135-40 and try again but last time I was getting over 63 fpe (not sure of number of shots as that was too high and I set the reg pressure lower) I was using this method with 95% and 33.95's..
 
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I’m still not sure what you’re chasing. Are you chasing really cool internet efficiency bragging numbers or a gun that shoots fantastic from fill to refill? If you are getting the speed that produces great accuracy at 95%, then your only other concern is does it do it across a full fill range. Internet or forum numbers/groups should be taken with a grain of salt. They are the main source of guys spending too much money on projectiles and gadgets. I can give you three recent instances where an owner told me his numbers. When I received the gun, not even close. Bottom line, just focus on your gun and what it will do.
 
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Vetmx said:
I’m still not sure what you’re chasing. Are you chasing really cool internet efficiency bragging numbers or a gun that shoots fantastic from fill to refill? If you are getting the speed that produces great accuracy at 95%, then your only other concern is does it do it across a full fill range. Internet or forum numbers/groups should be taken with a grain of salt. They are the main source of guys spending too much money on projectiles and gadgets. I can give you three recent instances where an owner told me his numbers. When I received the gun, not even close. Bottom line, just focus on your gun and what it will do.
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What? Really cool internet efficiency bragging numbers? I want 50 fpe with a good extreme spread.. Take it easy buddy it's almost Christmas.. Have some peace eh?
 
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MACTEN said:
I will set the reg up to 135-40 and try again but last time I was getting over 63 fpe (not sure of number of shots as that was too high and I set the reg pressure lower)
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Maybe I'm misunderstanding but it sounds like you want it set up for ~50fpe, and you're already there with the 120 bar setpoint and operating on the velocity knee. So why change it back 135-140 bar?
 
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nervoustrig said:
Maybe I'm misunderstanding but it sounds like you want it set up for ~50fpe, and you're already there with the 120 bar setpoint and operating on the velocity knee. So why change it back 135-140 bar?
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If I'm wasting air that means I can get a few more shots. I put it to 130 bar and am coming back off the knee to see what happens. If I'm pushing the fpe too far I'll return to where I had it.
 
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MACTEN said:
If I'm wasting air that means I can get a few more shots.
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By having already set it to the velocity knee, it is not wasting air. That is a direct relationship.

Once you increase the reg pressure, you will then again need to adjust the hammer spring tension to the velocity knee. The result will be higher energy and fewer shots. Granted you could simply increase the reg pressure and leave the HST where it is, but the extreme spread will be compromised.
 
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nervoustrig said:
By having already set it to the velocity knee, it is not wasting air. That is a direct relationship.

Once you increase the reg pressure, you will then again need to adjust the hammer spring tension to the velocity knee. The result will be higher energy and fewer shots. Granted you could simply increase the reg pressure and leave the HST where it is, but the extreme spread will be compromised.
Click to expand...
Yep.. Just figured that out. Lowered it back to 122 bar and am back about where I started. I actually think I need to tune this with 25.39's (which I don't have) and try to tune and shoot that pellet if possible to get the fps to around 880-900. I usually don't get those as the Huben likes 33.95's. I've only had regulated guns for a few years and my learning curve is steep.. Thanks for your information and patience with an oldish man. :rolleyes: Been shooting unregulated pcp's since late 90's and know how to tune those fairly well. When the weather breaks I plan to limp out to the range and try to sight in and get a good group.
 
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MACTEN said:
What? Really cool internet efficiency bragging numbers? I want 50 fpe with a good extreme spread.. Take it easy buddy it's almost Christmas.. Have some peace eh?
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Nervoustrig stated what I was eluding to. It sounded like you already had the gun dialed in at 120b. I just couldn’t figure out what more you wanted. You going back to a 25.39 could be a good thing. A 33.95 is a big jump in weight and depending on your barrel length and hammer weight, they might fight you a little. You made me do backwards math with your 33.95’s because you only said 50fpe, but I’ll bet you are going to be real happy with how your gun performs with the 25.39’s at 880 or so.
 
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Vetmx said:
Nervoustrig stated what I was eluding to. It sounded like you already had the gun dialed in at 120b. I just couldn’t figure out what more you wanted. You going back to a 25.39 could be a good thing. A 33.95 is a big jump in weight and depending on your barrel length and hammer weight, they might fight you a little. You made me do backwards math with your 33.95’s because you only said 50fpe, but I’ll bet you are going to be real happy with how your gun performs with the 25.39’s at 880 or so.
Click to expand...
I just didn't know with a small tune I would get over 60 fpe with this gun as I had read it's about a 50 fpe rifle, which I figured would be perfect for 50-80 yards. Seeing that it would only probably get two 16 shot mags with that power and maybe not be the best fps I wanted 50 instead.
 
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