Quote:
Originally Posted by 4 Scale
I have also been surprised at how accurate a poor bore can be, but believe it can be explained. My theory is, poor bores are caused by use (wear) and corrosion.
I invite challenges or corrections to this theory.
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I offer neither. I do offer more information...
A Luger typically is marked with an 8,82mm [.347"] designation. That is a land dimension. A 9mm bullet is .355" diameter. That gives roughly a .004" - .005" depth of rifling groove. It would be reasonable to assume that the land would wear more rapidly than the groove (it is subjected to pressure/friction more than the groove). So the land can wear significantly more without affecting gyroscopic stability or velocity. Which equals accuracy.
...In theory...
To put this in perspective for non-machinists, a sheet of ruled notebook paper is .004" thick. I use pieces of notebook paper for my metalworking.