I lap everything and never have a problem with rust, but more importantly, I never have ring marks on my scopes if I ever decide to sell them. I use a 350mm length of one inch 4140 chrome bar and value grinding paste for lapping and it does a very good job. Here's some pics from when I lapped the rings on my new 45-70 recently.





Rings prior to lapping.

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The finished product.

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