Fire one round and adjust sites to that impact
Have you tried their web site?
CMP, they have a web site that explains how to go about it.
No known web site.
No way to answer without the serail number.
Go to Remington's web site and request a manaual
Ruger has sn information on their web site.
Go to this site for informationhome.comcast.net/~jimringbauer/HamiltonRiflesindex.html
Go to Remington's web site. They have a list of repair centers.
Compare to others at a gun show, auction site, etc..
Contact Bushnell
Ruger's web site has sn data.
Remington's web site has a section with history on each of its products.