As you may remember I posted a problem with my new CVA Mountain rifle. The hammer was not clearing the nipple ( nipple not centered in the hammer cup.)
I know that you are not to try to remove the bolster from the barrel....but I tried this. Needing only to move the nipple back aprox1/16 inch. I placed the barrel in my bench vise and used a pair of vise grips to slightly turn it back.
Put the barrel back in the stock and now the barrel lines up perfectly. Went ahead and installed a new nipple.
Also found out something interesting. Different manufactors making the same nipple for a particular rifle are not the same overall length. quite a bit of difference in some.