(after verifying safe/unloaded) I start with gross anatomy first- overall impression of condition, previous owner's care or lack thereof. Has the stock been shortened or modified? Then I look at the muzzle and inspect the crown. Look for signs of improper cleaning or damage. Look at the screws for signs of "tinkering". If they didn't have a proper set of screwdrivers, they probably didn't know what they were doing when they opened it up for that do-it-yourself trigger job, bedding, etc. Take a bore light to inspect the chamber and bore from both ends, a bent barrel should be apparent while sighting down the lighted bore. Look the bolt over, check lugs and extractor for damage. Look at the scope mounting holes/screws closely for signs of stripped threads or broken off screws.
Also try to get an idea of the honesty or rep of the seller/dealer. If everything looks good, chances are better than even that you'll get a servicable rifle. There are a lot of good used rifles out there and more than a few lemons. some started out that way and some were bubbafied into junk.
The worst rifle I ever owned was bought new in the box. A couple of my best rifles were bought used. Give it your best going-over and then cross your fingers and go with your intuition.
Hope this helps.
