primary key constraint Sorting Is having a field in primary key constraint optimizes sorting of the table ?

Here's the schema of the table:

CREATE TABLE Persons (
Field1 long NOT NULL,
Field2 long NOT NULL,
Field3 long NOT NULL,
Field4  long NOT NULL,
Filed5 long NOT NULL,
CONSTRAINT PK_Person PRIMARY KEY (Field1 Asc,Field2 Asc,Field3 Asc,Field4 Asc));


The sorting query: Select * from Persons order by Field4

The field4 in primary key constraint doesn't provide any uniqueness with respect to values. 

The only reason it's added is to optimize the sorting on field4, since sorting on a column that does have an clustered index helps in optimization.

In short, Is having the field4 in primary key constraint helping with the optimization of the above sorting query, even though the primary key constraint is created using ascending order of field1 then field2 then field3 and the field4 ?
No, it won't help. If Field4 were the first column, then it would have helped. Like asking if going through a telephone directory/book will help you sort peoples names by firstname. :-)

Edit: Erik posted one example where this index can help. Requires you to return all of the rows for a certain Field4 value (i.e., equal-comparison on all but Field4).