There are cylinder throat gauges which can be tried in the fronts of each chamber of a cylinder, but an inside micrometer's better - since it will give you an exact measurement for each one (the cylinder should be marked to make finding a particular chamber easier).
There is also a tool called a Range Rod, which is sliiped downbore from the muzzle with the action cocked, to ascertain if any chambers are out of alignment with the bore.
Remedies for both situations would require more technical knowledge then is available to most gun owners, so I would suggest that you contact the Ruger Service Dept with your issue(s).
There has been a history of .454 SRH "troubles", and Ruger just might want to service your revolver for the bubble, and even send you a prepaid shipping label should you inquire about it.
FWIW, It is perfectly legal under Federal Law for ANY gun owner to ship/receive their own firearm (handgun included) to/from ANY firearm FFL, dealer, manufacturer or custon/repair facility, directly WITHOUT going through an FFL holder.
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