welcome and way to go on the buck, i owned a ruger m77 that fired on me when i closed the bolt, it was a used gun as well, and i could never get around that incedent with that rifle, since then i have owned five ruger rifles with nothing more than some trigger work needed, a local smith was very anxious to look at the gun, it was sent back to ruger where the bolt was replaced for free, and it turned out that the bolt had some previous bolt/weather damage from the previous owner and it was the first time i had fooled with the gun, lesson learned, thank goodness i was in a safe place with the muzzle pointed in a safe direction, again this was not a ruger problem but a previous owner problem, and i thought what the heck i'll take the thing out and see if it'll shoot[:-]
the fault was my own when I did not check out my used purchase well enough.
i can relate