[Chris Williams]

One thing to keep in mind about filling a smaller bottle (10oz) from a bigger one (e.g. 5 or 10 lbs) is that the larger bottle will lose pressure over time. This means the smaller bottle won't get to the full desired pressure. Most people think you should have at least 500lbs of pressure in the bottle, and run the valves at 100+. A 1/2 - 3/4ths used bottle may not have that kind of pressure, even though it may well have a bunch of CO2 left.

At something like $25-35 a tank for an exchange at a welding supply store, I swap the bigger bottle every season, regardless of how much is left in it. Cheap insurance to having more than enough pressure.