I ended up with about a gallon less beer than I intended on my last batch. Looks like Im only gonna end up with about 4 gallons of beer in a 5-gal corny keg. I was wondering… Would the extra gallon of head space affect the pressure needed to carbonate it if Im just pumping CO2 into it?
Nope.
no. pressure is pressure. It will carbonate easier/quicker though.
Not if you’re just letting it sit, the surface area is the same. 
Sorry - i meant with my method which is to top off with 30 psi for the first 2 days then top off with my desired psi until it won’t take anymore.
Do you put the 30 psi on and then take off the gas or is it constant 30 psi? Because constant it won’t go faster due to head space. But if you put it on 30 psi and then take the gas off, yes, it will equilibrate at a higher pressure. Or if you shake it it could go faster due to more surface area.
When I carbonate, I top off and then disconnect - this way I can figure out if I have any leaks before its too late.
When the kegs go to the serving kegerator, I leave them connected.
Sorry for the confusion - I just noticed that when I half filled a 5gal it carbonated much quicker given my method.
No worries, I’m just trying to understand in my usual dickish way. :) The way you do it, it should definitely carbonate to the desired level faster.
Not part of your original question, but as a reminder . . especially with so much head space . . .Charge and purge a couple of times to get rid of the O2 before carbonating.
Thanks guys!
One more question… a bit off topic…
Does anybody here use a keg as a secondary fementer/conditioning tank? I assume for beers where you’re going to be dry-hopping, kegs are easier to purge with CO2. Ive had bad luck with trying to dry-hop beers, and I hear that being able to purge out the oxygen can really help keep the fresh flavor.
If you use loose hops in the keg for dry hopping you might have issue with clogging the dip tube.
One way to prevent this is to put hops in bag and then suspend the bag from the keg lid.
All that said kegs are great for dry hopping.