I think the term overbore has been loosely defined by shooters/writers. One definition defines it as the relationship of the bore diameter to the case diameter, and relating this to barrel life. The other definition as been to describe a cartridge/rifle setup that uses more powder than rifle can efficiently burn within the barrel thus making for inefficient cartridge/rifle combination. The 6.5x284 has been described as being overbore, largely in the context of the first definition by the target shooting crowd. Compared to most of the cartridges used by target shooters, it does have a one of the highest ratios of case diameter to bore size and combined with it's inherently larger powder capacity exhibits shorter case life than the other cartridges. The reason that target shooters like the cartridge, and will trade off barrel life, is the combination of low recoil and superior ballistic performance relative to other rounds. Barrel life is a function of both powder charge and bore relationship. Under similar conditions, I have found the 6.5x284 no more of a barrel burner than most of the magnums that are commonly used, and better than some. As to being overbore as applied to the second definition described above, powder choice and barrel length play a role in whether a cartridge is actually overbore. For certain, being overbore using either definition has no influence on the accuracy potential of the 6,5x284, and tends to be a much less of a factor considering barrel life as far as hunting use is concerned. IMHO.
