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PostPosted: Mon May 10, 2010 7:07 pm 
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Location: Southern Ontario
Which gauge do you rely on, the one on your pump/scuba tank, or the one on your rifle?
The reason I ask is there seems to be a big discrepancy between the gauge on my scuba tank, and the gauge on my HW100SK's fill tube.
When the gauge on the tank states I'm full, the gauge on the rifle says I have a few hundred PSI to go.
What do you think?


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PostPosted: Mon May 10, 2010 7:26 pm 
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Location: Greater Napanee, ON, Canada
I would always use the gauge on the rifle, which will allow you to fill it from any tank or pump. You will find that the gauges on tanks and pumps always vary, but the one on your gun should remain pretty consistent. So find the sweet spot of your fill using the gauge on the gun and you'll be good to go.

Tim

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PostPosted: Mon May 10, 2010 11:07 pm 
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Location: Toronto, ON
It's always a good idea to use your rifle's gauge as the indicator for where you are in your 'sweet spot' range.

BUT for filling purposes, I've always used the filling tank / pump gauge. I've read in more than 1 manual, that using your rifle's tube gauge as the indicator for the actual pressure in the tube when filling shouldn't be done, because there could be a lag between the displayed pressure on this gauge and the actual pressure in the tube.

For example, if your tube gauge reads 180 bar at 9:35:27am, (your target fill) and you turn off the fill tank valve, by 9:35:45am, the gauge on your rifle tube may then read 200bar- so you've overfilled it past your target.

One way around this is to test out the lag time for your tube gauge. For example, fill it to say 150bar on the rifle tube gauge, then close the filling tank valve. Watch the tube gauge for the next few minutes... does it move at all?

I have a big honking 'test and calibration' gauge that I bought with the intention of building a 'fill tank / pump gauge' testing fixture. I've attached a picture of it.

It's built, but I have yet to test and calibrate its dial to ensure that it's accurate. My long term goal is to allow other shooters to use this fixture to see how accurate their gauges are- a lot of gauges I've come across aren't all that accurate.

Using it to test the rifle's tube gauge would also be possible, but would require a Y connector, which I don't currently have, but could be easily built with a T joint.


Attachments:
gauge.jpg
gauge.jpg [ 63.82 KiB | Viewed 536 times ]

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PostPosted: Mon May 10, 2010 11:19 pm 
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Location: Rocky Mtn Hse Alberta
I would not trust the value of the guns gauge but the mark it reachs on a fill is likely repeatable.

Any time there is a question it is wise to use the lowest safest pressure until proven otherwise.
So as suggested compare your fill whip gauge to a known standard and see how it goes.

Walter....

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PostPosted: Tue May 11, 2010 4:03 am 
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Location: Southern Ontario
pirellip wrote:
there could be a lag between the displayed pressure on this gauge and the actual pressure in the tube.
I considered this, so I stopped my fill based on the gauge on my tank. I let the rifle sit over night then re-checked, and the gauge on the tube was still reading the same.
Since the gauges on all my Air Arms rifles have pretty accurately matched what the gauge on my scba tank and hand pump have said, I guess the gauge on my HW is the one that's most likely off :x
Mac wrote:
I would always use the gauge on the rifle, which will allow you to fill it from any tank or pump.

What if the gauge on the rifle has me over-filling the tube??? :?
pirellip wrote:
I have a big honking 'test and calibration' gauge that I bought with the intention of building a 'fill tank / pump gauge' testing fixture.
I would love to try this some time!


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PostPosted: Tue May 11, 2010 9:09 am 
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Location: Greater Napanee, ON, Canada
Pumpmaster wrote:
Mac wrote:
I would always use the gauge on the rifle, which will allow you to fill it from any tank or pump.

What if the gauge on the rifle has me over-filling the tube??? :?


Like I said, if you check the gun for the sweet spot, you learn what point to fill it up to and shoot it down to. Does it matter if it says 190 bar and it is really 200 bar or does it matter that you always fill it the same and shoot in the sweet spot? For each of my guns, I know exactly where to fill it on the gun's gauge and at what pressure I will need to refill. It has worked for me and it is real simple, so I'm sticking to it.

For me it does not matter what the exact pressure is, partly because all my AA guns have a sweet spot well below the guns max pressure. My S400 SL fills to 170 bar on the gun's gauge and I shoot down to 120 bar. The high end gauge on the fill adapter/tank is fairly close to the guns gauge (within 10 bar), so I do not worry about it. Simple is always good for me. 8)

Tim

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PostPosted: Tue May 11, 2010 9:50 am 
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Pumpmaster wrote:
What if the gauge on the rifle has me over-filling the tube??? :?


The worst case scenario, for your Air Arms rifles specifically, is that the tube gauge will reach it's fail safe point (around 250 bar) and it'll dump all the air out, and ruin the gauge.

I am of the opinion that you can safely fill these tubes to 220 bar on a regular basis without worrying about any long term failures. I say this because Ben Taylor, a widely accepted PCP guru, designs his Air Arms tuned rifles for a fill to 220 bar on every fill. If it's good enough for Ben, it's good enough for me.

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PostPosted: Tue May 11, 2010 1:50 pm 
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my local dive shack's fill station has a 5" mid-west instruments piston guage.. says it's good for +/-5psi rated for 6k, and it's calibratible..

Only costs like 700bucks.

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PostPosted: Tue May 11, 2010 1:51 pm 
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My Logun Solo doesn't have a guage on the gun, so it leaves but one option...... :| .


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PostPosted: Tue May 11, 2010 2:34 pm 
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NBLongRanger wrote:
my local dive shack's fill station has a 5" mid-west instruments piston guage.. says it's good for +/-5psi rated for 6k, and it's calibratible..

Only costs like 700bucks.


As an Instrument Mechanic, I am most curious about such a guage? any links to one?

Walter....

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PostPosted: Tue May 11, 2010 5:30 pm 
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Mac wrote:
Does it matter if it says 190 bar and it is really 200 bar
My concern is over-filling the tube. If I fill the PCP tube to full (according to the gauge on the rifle) I will be significantly over-filling it according to the gauge on my scba tank.
pirellip wrote:
The worst case scenario, for your Air Arms rifles specifically, is that the tube gauge will reach it's fail safe point (around 250 bar) and it'll dump all the air out, and ruin the gauge.

This question is based on my new HW100SK. The gauges on all my Air Arms have always read very close to what my scba or pump gauge read.

Guess I'll just start chrony testing and see how many shots I get on a fill. That should help determine which gauge is reading closer to the truth. I'm just paranoid about high air pressure and my new toy :? :lol:


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PostPosted: Tue May 11, 2010 6:11 pm 
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Location: Rocky Mtn Hse Alberta
Pumpmaster wrote:
Mac wrote:
Does it matter if it says 190 bar and it is really 200 bar
My concern is over-filling the tube. If I fill the PCP tube to full (according to the gauge on the rifle) I will be significantly over-filling it according to the gauge on my scba tank.
pirellip wrote:
The worst case scenario, for your Air Arms rifles specifically, is that the tube gauge will reach it's fail safe point (around 250 bar) and it'll dump all the air out, and ruin the gauge.

This question is based on my new HW100SK. The gauges on all my Air Arms have always read very close to what my scba or pump gauge read.

Guess I'll just start chrony testing and see how many shots I get on a fill. That should help determine which gauge is reading closer to the truth. I'm just paranoid about high air pressure and my new toy :? :lol:


Let me see if I understand this....

You have AirArms airrifle(s) plural and you have a fill gauge that agree on a pressure 'number' and now you are filling a new HW100 that you have zero experience with and so are questioning all the prior colaborating information?

Does that make any sense to you?

You have three pieces of pressure instrumentation that agree and one that does not. Would it not be reasonable at this point to trust the three in agreement?

Do not use the HW pressure until such time as you PROVE it trustworthy.

Walter....

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PostPosted: Tue May 11, 2010 10:08 pm 
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Went by the shop, the mid-west is on the filter bank. The fill guages are ashcroft.

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PostPosted: Tue May 11, 2010 11:08 pm 
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Location: Greater Napanee, ON, Canada
Fill the HW tube using the gauge on the fill tank, since it seems to be the one you trust. Then see what the gauge on the HW reads and use that as a fill point from then on. That way you can fill from any tank, even if it does not have a gauge or if the gauge is different than the one on your tank.

Tim

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PostPosted: Wed May 12, 2010 12:15 am 
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Location: Rocky Mtn Hse Alberta
NBLongRanger wrote:
Went by the shop, the mid-west is on the filter bank. The fill guages are ashcroft.


that makes sense as teh Midwest are differential pressure and as you indicated piston style.

Ashcroft are quite nice gauges for sure.

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