Another way to force carb, albeit it not very accurate, chill down to about 4*c, transfer to the keg, then crank the gas up to 300kpa and 'shake and bake' the keg for approx 60 seconds ( 40 seconds for a bitter or similair) then turn the gas bottle off and shake the Co2 into the beer and stop when the guage gets down to around 100-160kpa... Wait an hour (or overnight) then vent the keg down to serving pressure and serve!
It takes a couple of days for the carbonation to come right, but its still drinkable straight away...
I do this every time, mainly cos im impatient and it means I can be drinking carbonated beer an hour after its into the keg :thumb:
Just be carefull when doing this that you dont rock the keg for more than 60 seconds or you will overcarbonate which isnt cool...