On thin touchhole liner faces and barrels

[TANSTAAFL]

Did not want to hijack a current thread on TH liner erosion from thin face of liner, so started a new thread.

All this brings up something I find interesting. It is pointed out about the dangers of dove tails for sights & underlugs being cut too deep, resulting in a thin barrel in that area. Yet, considering the bore curvature, (O) it would be a very small area that is actually thin.

So, why it is fine to shoot thousands of rounds with a internally/externally coned drilled thin faced TH, or, with a 20-30 thou touchhole liner face, yet, it is a bad thing to have a much thicker thin spot in a barrel?

 

[Cherokee]

good point

 

[CoyoteJoe]

Because of the tapered cone of a vent liner the actual thin spot is just at the vent itself, the surrounding metal rapidly thickens as you move out from the center. That would be a very small area, much smaller than the "thin spot" under the dovetail of a large bore rifle.