Quote:

“I don't know. It would be interesting to find out if NEW {sharp-land} barrels are LESS susceptible to OSR than old {or rounded-land} barrels. ”

NOPE!!! The OSR I personally experienced was with a brand spanking NEW Weatherby MK V in .378 Weatherby. Hardly a worn out soft steel equipped withering flower of a rifle....

I really think OSR results from high pressure caused by a bullet that does not allow the barrel lands to properly displace the bullet material, either through or due to a combination of hardness, size and design. It is generally desirable to use non jacketed lead bullets oversized by 0.001 or 0.002, and these bullets do not cause OSR.

In the case of monometal solids, they are far harder than plain lead bullets, or gilded jacket bullets. My hypothesis is that the barrel lands simply cannot displace the monometal bullet material appropriately and or quickly enough and maybe an overly high pressure wave follows the bullet on it’s path all the way down the tube, displacing barrel steel all along the way. This doesn't seem to happen with monometal bullets equipped with stress relief grooves, and following the hypothesis above, they simply do not cause high pressures of examples with no stress grooves......

Without an elaborate test scenario to back up or test out the hypothesis, we may never know. Suffice to understand the Barnes X without stress relief grooves will almost certainly bugger your barrel.