Stock .25 Synrod with Mac1 Tune - Early Impressions and a Question

[cgish]

This is my first PCP, and first air gun bigger than a Daisy 880. It came from Mac1 with a shroud and a tune that focuses on the barrel and trigger.

I purchased a Competition Electronics 539009-SSI Pro Chrono Pal and the companion Competition Electronics 541002 Indoor Light System for measuring FPS.

This gun has less than 100 shots through it. It took about four clips, or 24 shots for the POI to stabilize, which is exactly what Tim predicts in his description of his tune.

Here are the measurements from four clips worth of shots, two clips of JSB 33.95's and two of JSB 25.39's. I started with a full air chamber (3000 psi) and shot the first two clips, then refilled the chamber and shot the second two clips. The pressure after 16 shots was about 2500-2600 psi on the gun's gauge.



I have not shot the gun on down to a lower pressure yet. I have to get down to the farm for a few hours to finish sighting in and record a full string of shots.

QUESTION: There is about a 400 psi difference between the Synrod's pressure gauge and the gauge on the Hill Pump MK4. The pump reads about 2600 when the gun shows 3000. Is this difference normal?

EDIT: Reading the forums, it seems it is normal for there to be some difference between the two gauges. However, I am seeing a lot of approximately 200 psi differences in the results I am reading.

SO, is 400 psi out of line?

AND, is the larger gauge on the pump likely to be the more accurate of the two?

Thank You,
Cody

[triggertreat]

Yes it is common to have these differences in the gun gauge.  I replaced my Crosman gauges with a much better gauge and the problem went away.  I would go by the pump gauge as they are typically more accurate.

Here is the gauge I use on my two Synrods.  It is simple to replace.

Marauder replacement gauge 4000psi
 

[cgish]

Thank you. I'll have a look at those gauges.

[HunterWhite]

My 25 Synrod gauge reads 250 psi lower than my tank gauge. 3000 on my tank when my Benjamin reads 2750. I fill to the point where the velocity is up on the curve.

[KnifeMaker]

Good gages, but they list +_ 5% which is up to a margin of 300 psi  at 3000 psi.


Not exactly precision. Wonder if there are better out there?


Knife

[cgish]

Good gages, but they list +_ 5% which is up to a margin of 300 psi  at 3000 psi.


Not exactly precision. Wonder if there are better out there?


Knife

Thanks Knife ... I missed that when I looked at them.

On the plus side, that would be a lot better than the +/- 13 to 14 percent I currently have ...

Cody

[jarmstrong]

Ya, but, at 3000psi true pressure, the gauge could read anywhere from 2850psi to 3150 psi (300psi swing)
you would at most be 150psi off at 3000psig,

[HunterWhite]

I worked in the electronics business for 30 years.  When they make components in various tolerances they just make a bunch. They sort them, then sell the 1%, then they take out the 5%, then take out the 10%. So if you buy 10% parts you will get greater than 5 and less than 10 percent tolerance.  If they sell 1%, 5% and 10% then the 10% will not likely be within 5%.

[Tricker]

Triggertreat's link showed a 750 psi gauge , I'm sure he meant the 4000 psi gauge ,same size as Marauder original but needle sweeps 110 degrees across face for 0-3000 psi and is more accurate just by that detail. I have two on my cascade tanks, one on my USFT. Between those three, pressurized simultaneously at 3k psi there is less than 100 psi variation. That's about 3%.  I had Ninja gauges that vary as much as 700 psi between identical gauges, have replaced them all on Marauder and  Ninja regulated USFT and scuba fill yokes.   Tom

[triggertreat]

Tricker, in the link I put 4000psi, but the link goes to the main page where you can select whichever one you want.  I selected the 0-4000 because the labeling seems less compressed than the 0-5000 and is easier for me to read.  I can say that my two gauges match up to my two fill assemblies and have for a couple of years now unlike the Crosman gauges they replaced.

[HunterWhite]

I would really like to find a better gauge for my Marauder.  Airtanksforsale does have a good quality stainless steel gauge,  but it's just about 80 degrees of scale to 3ooo psi.