May wish to try at 50/100 years also to get an idea of how far off you are. At that time you could try the iron sights and possible another scope / red dot from a friend.
Before I started to shim, would first take the mount / rings / riser apart and check the contact surfaces for any lumps/bumps/material (possible carefully clean the contacting surfaces).
Then when I was putting all the mounts back together, would wiggle each matting surface a fraction of a mm while putting toghter - to get the best contact (along the lines of putting in a screw which is slightly misalignment).
In connection with front sights, most of us end up with some type flip up rear sight (ARMS #40 is nice or the Kights 600 meter sight is you are into longer ranges ;-) and keep the front sight. Would recommend doing a search on AR15.com for "front sight" and setting the time frame to max (30 days most likely).
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