hoosier - all the above is correct. Two tips -
1. Don't pay some dim wit at a shop that doesn't a clue of what they are doing (though they will tell you they do) to do this. Make sure the base is alinged with the bore, make sure the base is flat and does not move around. Make sure you have plenty of eye relief. Make sure your cross hairs are vertical / perpindicular.
2. Before using blue lock tight - pull the bolt out, mount the base, check for flush fit, bottom out the screws - reach into the chamber and check with the tip of your finger to make 100% certain that the screws aren't gonna be gettin whacked by the bolt.
It is easy stuff - just see the problem before it happens.
Good luck.