There are several causes for throw-by. All require some knowledge to correct. It starts with a badly timed bolt, badly fitted bolt, bad trigger/bolt spring, wrong trigger/bolt spring or .......... a combination of ALL of the above. A competent SAA guy needs to look at the guns. For the new one, it comes with a warranty. Use the warranty.
I don't mind separating folks from their money when necessary, but use the warranty. Also, ask the warranty folks if they will look at the older one. Some times they will fix them for free if it is obvious the gun was not set up right to begin with.
It's real easy to really screw up a SAA if you don't understand how they work and time. If you haven't worked on them before, for every part your going to touch, call VTIgunparts and order two new replacement parts. You'll need 'em.
Coffinmaker