Fire_Moose says he is interested in a .308 caliber bolt action sporter. Such a rifle is almost certainly not going to have any throat erosion.
Respectfully disagree with this assertian - it will depend on the use a rifle has had and checking a bore for signs of wear to the throat, leade, crown etc are all buyers 101. A sporting rifle may have been used in Target Rifle competitions, field class for instance, which is common in my part of the world and .308 is commonly used for that competition. Many target shooters change out barrels after 10,000 rounds ... because of wear.
When a buyer comes up on a 2nd hand rifle he has no clue how it has been used. Depending on the loads a shooter is using also, throat erosion may be better or worse ... hot loads can vastly excellerate throat erosion. Giving a man all the tools he needs in order to check the quality of a 2nd hand rifle for purchase is what we are about here, not limiting his vision of what might or might not - "probably" - be the case.
Suggesting that checking a bore is a waste of time since when dirty they all look alike (#17) is not what I call smart practice. I've looked down plenty of dirty and dark bores and seen as many variations of condition as there are stars in the sky. If the OP wants to be casual and take a pot shot at a second hand purchase, it's his money and his decision, but as a fellow shooter I feel a duty of care to give a bloke as many tools as he can handle to help in his decision making process ... not less.