Peter is talking about Paul's epistles here which contain our doctrine for this age of grace. Peter found it hard to understand how the Lord could go to the gentiles after he told them earlier not to. People were and still are twisting Paul's gospel and trying to tell people we are still under the law. Even Peter is saying here that the longsuffering of our Lord is salvation.
In verse 17 he clearly says that this occurs with both Paul's epistles and other scripture.
Salvation yes, but not necessarily redemption.