i've had a bit of a problem with filling a large 11lb bottle. It's a nice shiny new luxfer, pie marked bottle. had been leak tested with compressed air to about 150 psi, not ideal but apart from filling how else can you check?
Far from ideal and the best way for Joe public to test a bottle is to fill it with nitrous GAS (only) and then immerse the top of the bottle in a bucket of water.

Any way i took it to shakey to get filled by ............(i'm sure you know who i'm on about they only do NOS) who are there at most meetings they had a grumble about the bottle type and the highpower fittings but after some messing about managed to get just 5lb in. told me that luxfer type bottle meant for co2 so possibly will not hold the 11lbs that you might think it should. only had to pay for 5lb so no real harm done.
The fact the bottle has CO2 stamped on it is of NO CONSEQUENCE to its use for nitrous, so that shows how little that guy knows, which probably explains why he sell HolleyNOS gear.

So rather than keep all my eggs in 1 basket so to speak i immediately went back to the van and filled my 2 small (20oz & 16oz) bottles all went well.
having done a bit of messing around and the static testing the 20oz was low so thought a top would be a good idea, bottle in freezer over night, hooked up to filler sat on scales -bit of a hiss..... then nothing! no weight gain nothing! all thats left in 11lb bottle is gas!
First of all you can't avoid approx 2 or so lbs of nitrous ending up as gas, as that's what the GAS weighs in a full bottle. The ONLY way to avoid wasting it is to top up bottles rather than empty and fill.
That is assuming that the dip tube is optimum length and does not leak.
Other potential causes for less than expected liquid being dispensed from the bottle are;
1) Short dip tube
2) Leaking dip tube
3) Leaking valve

hi brett yes watched them do everything, they fill on the scales so you can see whats going in. They use a pumped system so they shouldn't have any probs at all but they just couldn't get any more in.
I suppose they could have run out (of liquid?)
If they couldn't get any more in then they had run out of liquid in their bottle.

then last night my TIG welder died, disconnecting everything to ship for repair it dawned on me that i had a cheaper (than n20) pressure source with which to check to working pressure, 1500psi of argon.... GUESS WHAT!!!!!!

YEP AT 500psi I'VE GOT A LEAK very small but obviously enough
That would explain it.

Tap out,clean "o" ring and mating surfaces and sorted.
No more leak
looks like i've solved my own problem. if anyone thinks there could be anything else going on don't hesitate to let me know. All this learning the hard way could get expensive, i guess i should be grateful that they could only get 5lb in.
WE live and learn right off for a refill.
Correct you were lucky to lose so little and learning the hard way costs a great deal, so think yourself lucky that I did most of that for you (and all my other customers), because you wouldn't be happy having to pay for all I've had to learn in 30 years, to make it easier and cheaper for you guys now.