The  three main points you that will help your CO2 bulk filling are;  

1. For the bottle or gun you're filling to be colder than the bottle or cylinder you're filling from

and

2. For the connection between the source and destination to deliver liquid CO2

and

3. To keep the gas path volume as small as possible.

 

The reason these points will help you are;

1. The warmer bottle will have a higher gas pressure than the cooler one, gas delivered to the cooler bottle at the higher pressure will condense into liquid - this assists in achieving the maximum amount of CO2 transferred as the transfer completes at the end of the fill cycle.

and

2. Delivering liquid CO2 achieves the transfer of as much weight of CO2 as possible as quickly as possible in the first phase of filling.

and

3. Minimises liquid gas waste in the pipework on disconnection and improves fill efficiency by reducing gas warming in the transfer.

 

The best ways for you to achieve the above points are;

1a. Don't keep your source of bulk fill CO2 somewhere cold, you need to keep it below the marked safe temperature on the bottle but it won't hurt to keep it in the corner of one of the warmer rooms in your house, make a cover that matches the soft furnishings if you think your partner my object! ;-)

1b. Cool the gun or cylinder you wish to fill, guns will cool in use on the range and both guns and cylinders can be vented to chill them slightly for filling.

1c. Cylinders can be chilled in a refrigerator or freezer to achieve a maximum fill.

2. Fire extinguishers and other Dip-Tube cylinders should have the valve at the top, pub and other conventional cylinders should be safely supported inverted, with the valve at the bottom.

3. Use as direct an adapter or coupler as possible - all major CO2 Pistol manufacturers' OEM systems use direct bottle couplings and this is the most efficient type, where a hose is necessary keep it as small a bore and as short as possible.

 

So now you're ready to bulk fill

1. If the source cylinder is not warmer than the item to be filled then chill the gun or cylinder to be filled, empty guns can be part filled and vented to chill them if necessary but this does use up some gas for cooling.

2. Securely connect your CO2 bulk fill adapter, and gently open the cylinder valve, watch for leaks and be ready to shut off if gas is escaping.

3. If everything is gas tight open up the valve and let the CO2 transfer, leave the valve open for a minute or two, you aren't just waiting for a quick squirt of liquid to transfer, you're waiting for the higher pressure in your warmer fill cylinder to do the work and make most of the gas in what you're filling condense to liquid CO2.

4. Fully shut off the fill cylinder valve and disconnect in accordance with the gun/cylinder/coupling manufacturer's instructions, most pistol adapters are designed to safely discharge gas as they decouple, anything using a quick connector will be depressurised with a valve or at the cylinder connector.

5. Check weigh, that way you'll know how much gas you're getting into your cylinder or gun and if it's over full you can vent it to a safe level, on the other hand if you aren't achieving the transfer you should be you can trouble shoot your fill proceedure, you'll also be able to calculate what your gas consumption is per shot.

 

Important! - Know the capacity of your guns and cylinders and check weigh them after filling, if an over filled gun or cylinder is subject to a temperature rise the liquid can expand to eliminate the gas space an result in a pressure rise dramatic enough to cause an explosion!