I think you have a faulty bottle.
Nothing wrong with the 'squealing noise as has been explained earlier.
You charge the bottle to 232 bar quickly. You then switch off the tap and the pressure will settle back down a bit. Feed more air in until it stabilises at 232 bar. If you feel the bottle it will seem a little warm-this is normal.
Didn't you get any instructions when you bought the rifle? We are talking about one of the best FAC air rifles available and they normally are supplied with proper filling instructions.
Good shooting with it-enjoy!
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