I'm sure I saw a post recently that gave the size of drill and tap size for tapping a case to use with the Hornady OAL guage. I've searched with no luck, probably using the wrong criteria for the search. Can someone give me some info.?
The Tap size is 5/16-36. I use an "L" drill. There are some potential drawbacks to using a fired case. It may be a tight enough fit in the chamber as to make it difficult to be sure that the case is inserted all the way in to the chamber. It you have a body die that does not resize the neck it works best if you size the case without setting the shoulder back for the most accurate measurement.
