The purpose is to eliminate light strikes. That being said, many don't use it when running the 13#. BUT, CGW does say that you also need to run the reduced power FP spring with the 13# hammer spring to avoid light strikes.
So, a lot of us just throw in the extended FP since we have to take it out to change the spring anyways[emoji6]
And then of course it's the snowball effect, might as well add the CGW FP stop roll pin, reduced power FP block spring, modified block lifter, T2 disco, etc. etc.
Bwahahaha, it's an addiction I tell ya. [emoji2][emoji2]