The amount of free bore in any individual production gun is going to be different from one gun to the next. The amount of free bore is dictated by how the reamer is ground and to what dimensions. There is some conventional "wisdom" that states that a gun cannot be accurate unless there is minimum free bore. While there is some truth to this, it is in no way set in stone. Generally, production rifles will have this free bore as a liability issue, and the vast majority will exhibit spectacular accuracy. The manufacturers have to ensure that the guns can be used with any available production ammunition, and the free bore allows for a small amount of space to alleviate pressure for the hotter factory loads.