The accuracy life of a barrel is very dependent on how hot the barrel is allowed to get while firing and how well the barrel is cleaned.A barrel that is heated up constantly and not allowed to cool between shots will usually lose accuracy after only a fraction of the rounds of a barrel that is not allowed to overheat and is properly cleaned.According to several barrelmakers a stainless barrel is slightly more resistant to barrel erosion than a chromemoly barrel so it will have a slightly longer barrel life.

So the bottom line is that a a 300ultramag barrel that is not overheated and is cleaned properly could maintain it's accuracy for 1000 to 1500 rounds or possibly even more, while a barrel that is overheated may become inaccurate after only a few hundred rounds.