Taken from 'The Guns of Normandy'by George G Blackburn this account is for 25pdr guns.
"A troop,rolling down the road "on wheels" goes into crash action the moment the Gun Position Officer (GPO) receives over the radio the map reference of an unseen target miles away,with the order "Right ranging...Fire!"
To the GPO,who has been assiduously following his map to ensure he knows exactly where he is at any given moment,that message means:Get your guns deployed in the nearest field and put them on line to that target,using your map,your compass,the dialsight of your pivot gun,and a local aiming point;and then give them the range so your pivot gun can get off a ranging round that will land on or near the target,which your troop commander can see and use to complete the ranging.
Every troop in the Regiment can routinely bring its guns into action and get off the first round within three to five minutes of receiving such a target while travelling along a road.(Three minutes if there is no unusual delay because of the terrain)."
Presumably that delay would be slashed quite a bit if the guns were already set up,but I'm still reading the book and haven't come across that yet.