Author Topic: Reg string going downhill  (Read 483 times)

mcoulter

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Reg string going downhill
« on: February 25, 2018, 04:17:52 PM »
OK, my hopes of getting better regulator performance out of my Royale went down hill after getting my tank topped off and filling to 220 BAR and shooting through a couple of fills.   I'm just about ready to ditch the FX regulator and order a HUMA regulator.  This is what I'm seeing.  Sorry i have not transcribed them into a digital file...

In short I'm getting decent consistency from 220 BAR down to about 160 BAR.  The regulator should be set at 140 BAR.  I'm bummed at the velocity drop between 160 BAR and 140 BAR:



If you can't see my chicken scratch, here's a rough summary:

220 to 170 BAR = 880 fps
170 to 160 BAR = 875 fps
160 to 150 BAR = 860 fps
150 to 140 BAR = 845 fps

My next fill was similar in that it dropped pretty significantly after 160 BAR too.  Hammer spring tension was 3.5 turns out during these two fills.

Just for fun I did play bit with HS tension in the next 220 BAR fills. 

4 turns out = 867 fps
5 turns out = 830 fps

Any suggestions on things that I could do with the regulator would be appreciated. BTW, I have 2 FX regulators .  They (FX) sent me a new one after my original started doing the same thing.  So I can play with one of them without taking my rifle totally out of commission. 


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rsterne

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Re: Reg string going downhill
« Reply #1 on: February 25, 2018, 06:00:51 PM »
The first thing that comes to mind, is that the setpoint is actually closer to 160 bar than the 140 you think it is....

With the velocity drop you are seeing at 220 bar as you reduce the hammer strike, you are below the plateau of the velocity curve... The fact that you are not seeing an INCREASE in velocity as the gun drops off the regulator tells me you must be on the knee.... This means, to me, that the tune is about right.... probably even better at 4 turns out than at 3.5 turns out.... I think your setpoint is just higher than you think it is.... Only a pressure gauge on the downstream side will tell you for sure....

Bob
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mcoulter

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Re: Reg string going downhill
« Reply #2 on: February 25, 2018, 06:52:37 PM »
Thank you Bob.   Lowering the set pressure should be pretty easy.  (At least from the videos I have watched.)

One other observation, I have noticed the pressure drops 20 bar on the 1st mag, and the more like 10 bar on subsequent mags.  Is this typical ?
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rsterne

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Re: Reg string going downhill
« Reply #3 on: February 25, 2018, 09:50:00 PM »
You are likely seeing cooling in the reservoir on the first mag.... The temperature drop from the air expanding causes the pressure to drop.... particularly if you just filled the gun.... VERY common if you don't leave the gun to cool down and then top it up and leave it sit again so that it actually HAS 220 bar in it at room temp....

Bob
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mcoulter

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Re: Reg string going downhill
« Reply #4 on: March 01, 2018, 09:39:13 AM »
The first thing that comes to mind, is that the setpoint is actually closer to 160 bar than the 140 you think it is....

With the velocity drop you are seeing at 220 bar as you reduce the hammer strike, you are below the plateau of the velocity curve... The fact that you are not seeing an INCREASE in velocity as the gun drops off the regulator tells me you must be on the knee.... This means, to me, that the tune is about right.... probably even better at 4 turns out than at 3.5 turns out.... I think your setpoint is just higher than you think it is.... Only a pressure gauge on the downstream side will tell you for sure....

Bob


One more set of data to consider here.  I did some chrony testing earlier this winter with the same regulator but with the old seals.  I'm glad I noted my HS tension in my notes.  As you can see the velocity wasn't that much higher.  (I don't think that I have ever gone tighter than 2.5 turns out.) 

If my regulator truly was set at 160 bar, wouldn't these velocities at these tighter HS tensions be quite a bit higher than they actually were?

JSB 14.3
Hammer spring tension = 2.75 turns out
High power = 900 fps
Medium power = 704 fps
Low power = 550 fps

JSB 14.3
Hammer spring tension = 2.50 turns out
High power = 947 fps
Medium power = 722 fps
Low power = 570 fps

JSB 18.1
Hammer spring tension = 2.50 turns out
High power = 900 fps

Crosman Premier Domes 14.3
Hammer spring tension = 2.50 turns out
High power = 928 fps
Medium power = 715 fps
Low power = 560 fps

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mcoulter

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Re: Reg string going downhill
« Reply #5 on: March 03, 2018, 05:24:42 PM »
I shot a new string today.  This was after removing my "new" regulator and installing a new internal (high-pressure side) o-ring.  I marked the internal allen head and nylock nut and when reinstalling it I left it 1/4 turn more loose. 

Still not *great* but better...  I think I will loosen it one more 1/4 turn next time.  The hammer spring tension is at 4-turns out.

Oh, please note that my chrony was positioned about 14 feet away to get the light I needed.  I typically add 10 fps to get the "muzzle" velocity.

Data = https://docs.google.com/spreadsheets/d/1I9l6ov3H_pBKRfyChxxdm7kuyA3oKCck-atLplu98x4/edit?usp=sharing

If you check out the spreadsheet I think my cutoff is about 60 shots and in this case it was 150 bar.  So if Bob's guess about the reg being high is correct, the 1/4 turn dropped the reg/set pressure 10 bar and maybe another 1/4 turn down will drop it to 140 bar...



Oh yeah, we also got some snow yesterday  :-)



Ignore the center group.  That was from my d48.  Distance 40 yards.  There is another platform of logs under the log you actually see.




12-shot groups:




And a plain sheet of paper with red magic marker dots is now my favorite target...


« Last Edit: March 03, 2018, 05:37:35 PM by mcoulter »
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Motorhead

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Re: Reg string going downhill
« Reply #6 on: March 04, 2018, 09:07:56 AM »
Is this a FACTORY regulated gun ? ... or one where you ADDED a factory reg to it ?

* If added, did you drill out and open up the atmospheric vent hole ?
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Scott

mcoulter

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Re: Reg string going downhill
« Reply #7 on: March 05, 2018, 12:18:25 PM »
Motorhead, this is a current model, factory regulated gun.  In fact, this is the 2nd FX regulator that I have had in the gun.  The performance is good for a few months and then goes down hill.  But what I can't say is if this performance is "normal" for cold-weather shooting (5f to 40f).
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