Not quite 5 gallons

[gallowd7]

Just put some cider in a keg last night. This was my first keg in about three years so I am a bit rusty.
Here's my question/problem: I ended up with about 4.5 gallons in the corny. I am going to naturally carbonate, so no CO2, just sugar. Obviously there is a bit more space on top of the beer, so I shot a "little" CO2 into the tank to "fill it up". Should I have done that? What can I do in the future when I want to naturally carbonate and don't have 5 gallons?

I am also going to post on the brewing board about getting 5 gallons.

Thanks,
DaveG

[fuji6100]

Actually, giving your corney a "shot of co2" is exactly what you need to do to seal the lid. If you skip that step, all the co2 produced during natural carbination will seep out.