The chance of a bolt is mostly down to the fox, the earth it is in and the position the dog enters. A willing terrier can force a quick bolt but if it is in a stop, to create a bolt would mean the dog has given ground. Different if its mid tube. Bolting dogs are very useful dogs in certain hands. E.g in deep places on steep bankings. And they shouldnt be overlooked. But theyre not in the same league as a digging dog and definitely shouldnt be a goal to breed towards.