Are you speaking about a 1911?
and why would you need to change the main spring cap if that is what you are talking about?
IF a 1911 I can/t see where that would make any influence on a safety in a 1911 as all that it does is hold the hammer spur in place under spring tension.?
maybe I am missing something here?
list what weapon that you are asking about.
are you possibly asking about the mainspring housing??
or the mainspring cap???