Meandcoco that is a good question cause more than the barrell comes into play.My BLR in 358win makes a great 2 shot group but 3 shots bring it out to a little over1 inch or close to it but more shots and my group extends to 2 inches.the barrell gets hot and the wood around it changes with the heat,and starts putting pressure on spots that change the barrell harmonics,a out of shape stock fore arm will put pressure on the barrell.As a bullet is fired that point of movement is a node and center of distance is a node and at the muzzel is a node,if you could see the vibration patterns you have under tones and over tones.As these over tones and under tones start,the accuracy is when both over tones and under tones meet at each node at the same time and place,if wood grows and puts pressure on a given spot,then the whole vibration pattern is distorated and no accuracy can be achieved.So the heat of the barrel is not as important as pressure points due to heat,after I have relieved the stress on the forearm I wait 1 min between shots.I hope that helps.Drop-Shot