Rear tank gauge

Hi All,

First time here…

Reading some posts over the last couple of days, learning and having fun simultaneously, I decided to tell also my experiences.

I think that for a PCP tank, a gauge is a must.

Although I have used the gauge mounted in the neck of the bottle, it does not pleasing me 🙄 for two main reasons:

1º The gauge in the bottle neck is very small, and difficult to read (and the useful zone of reading even more) and I believe that it is not accurate enough.

2º I dont like the the asymmetric protuberance of the gauge in the bottle neck turning around while I screw the tank on. I see it fragile and dangerous if it receives a blow.

Then I decided to mount a real good gauge in the only position that is possible: the bottom of the bottle.

To do it, is indispensable to do drill a hole in the thank ( this is forbiden in some countries), but as a experiment I decided to take the risk, but with the due precautions of safety .Please note that I don´t say to anybody to do that.

The first thing of all, to locate a suitable gauge. In my case I had to order it do, since I did not find what was searching in the shops of pneumatic and hydraulics.
In two weeks they made a gauge of 40 mm of outside diameter and 250 Bar on a large scale, with a rear thread of 1/8 G and 11mm length:

After, measure and verify the thickness of the bottle bottom wall,mesuring the outside and after the inside, I found that the wall thickness is 7 mm. More than enough for my purposes.

Afterwards, centre the tank on the lathe as best as possible and drill and thread the wall of the bottle….Yes, as natural as it sound , a hole in the bottom. 😀
For cutting the thread I help my self with a little drop of cutting fluid.

Nevertheless I do not want to allow that the whole pressure of the tank should push on the threads of the gauge and I decided to install a nut from the interior to hold safely the gauge. It has also an O ring to avoid leaks: 😉

I had to do also the special key for this nut:

To install the nut inside the tank with the special key, was tricky and difficult due to the narrow space, and especially because you work blindly!! 😕 😕 😕

Once installed the gauge and its nut, I protected the whole assemble with a cover of aluminium specially designed to embrace the tank and to protect the gauge of possible shock and blows.

In addition it gives more resistance to the whole set. And it gives me the confidence of not having the gauge sticked into my shoulder.

Before installing it, I tried that the gauge fits very nicely inside its new housing:

Once quite mounted, the test-proof of pressure was satisfactory, I sprayed the tank rear with soapy water,charged the bottle very slowly, no bubbles at all, and for 20 days I left the tank loaded on 200 bar without losing only one bar of pressure. 😀 😀 😀

Already I have neither to count pellets nor do calculations simply I begin to shooting in 185 bar and finish on 100 bar. With good consistency of speed. I also have a good control of the presure while charging from the scuba. 8)

At the same time as I began this project, also I did an anatomical butt adjustable in length and height to do more ergonomic the set. Also it protect the glass gauge when not in use.

The screws that hold the support of the butt to the bottle are nylon pointed, to not damage or to create points of pressure on the surface of the tank

And this way there stays the whole set mounted and ready to shoot.:

Postscript
I do not recommend to anybody to do the same thing that I have done, since this is potentially dangerous specially if you dont have the proper tools….And knowledge

Each one calculates his own risk and do in consequence

Hope you like it