25-06

Not to get too far off-thread, but by pretty much any measure, the 25-'06 is "overbore". There have been many attempts to quantify this term, a very good example of which was penned by our own Rocky Rabb. The one I like is described in the chart found here:

http://accurateshooter.wordpress.com/2008/05/05/overbore-cartridges-a-working-definition

When you consider the 25-'06 has more case capacity, for it's bore size, than a 220 Swift (long reputed to be an overbore, barrel-burner) it is hard to not acknowledge that, if there is such a thing, then the 25-'06 cartridge is certainly guilty of being overbore. In fact, aside from the recent WSM/WSSM offerings, and some of the very long-throated Weatherby rounds, the 25-'06 is among the very worst commercial cartridges, where this nebulous term is concerned.

With that being said, a well-kept 25-'06 barrel that is not over-heated with full-throttle handloads, or by fast and furious prairie-dog annihilation, ought to retain its accuracy for many years and thousands of rounds. Which is to say, as alluded to previously, "overbore" and "shot out" barrels are really only relevant if you're shooting bench rest competitions or enjoy varmint hunting on a regular basis.

The term "overbore" refers to a condition wherein the case capacity of a given cartridge is excessive, in relation to the diameter of the bullets fired down the bore of a rifle so chambered. This term is nebulous, hence it cannot be quantified in precise dimensions, but there are certain symptoms which identify this condition, such as throats that erode more rapidly than other cartridges of like caliber and, perhaps most notably, nominal increases in velocity, despite large increases in powder! If you look at the ballistic efficiency of your 257 Roberts, in comparison to the 25-'06, you will see that the Bob achieves 94.6% of the velocity of the '06, while using only 87% as much powder (75gr bullet, IMR-4064).

Would a full-length 375 H&H, necked down to 25 caliber and blown out to a 40 degree shoulder, be overbore? How about an 8mm Rem Mag necked down to 17 caliber; would you agree that such a monster would meet the definition? What I'm asking is, do you even concede that there IS such a thing as a given cartridge being overbore?

I'll say it one last time: If such a condition as "overbore" does exist (which seems to be in dispute, here) the 25-'06, by any measure, would be guilty of such.