To be honest I have not read ed. 4 and 5 from cover to cover but e.g. I noticed that 2-J-3 changed: 4th Ed. has short A-D items, the 5th dropped the Aiming Point delivery line, and 6th went to two very long paragraphs A and B.
Thank you!
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I could be wrong. I have been before, and will be again.