Changing order of NSMutableOrderedSet CoreData relationship

I am trying to replace objects in a many to one ordered CoreData relationship... My code is here:

NSMutableOrderedSet *battingLineUpTemp = [battingOrderToChange.battingOrder mutableCopy];
    NSUInteger newBatsmanIndex = 0;

NSLog(@"Original batting order");
for (CricketPlayer *p in battingLineUpTemp) {
    NSLog(@"switching : %@ %@",p.firstName, p.lastName);
}

for (int i = [innings.wicketsFallen integerValue] +2; i < [battingOrderToChange.battingOrder count]; i++) {

    //[battingLineUpTemp replaceObjectAtIndex:i withObject:batsmenArray[newBatsmanIndex]];
    [battingLineUpTemp replaceObjectAtIndex:i withObject:[batsmenArray objectAtIndex:newBatsmanIndex]];
    newBatsmanIndex++;

}

NSLog(@"Changed batting order");
for (CricketPlayer *p in battingLineUpTemp) {
    NSLog(@"switching : %@ %@",p.firstName, p.lastName);
}


[battingOrderToChange willChangeValueForKey:@"battingOrder"];
[battingOrderToChange setBattingOrder:[[NSOrderedSet alloc] initWithOrderedSet:[battingLineUpTemp copy]]];
battingOrderToChange.battingOrder = battingLineUpTemp;
[battingOrderToChange didChangeValueForKey:@"battingOrder"];

Yet the second time i output the players names I get the exact same result as beforehand! I have made sure that the NSArray (batsmenArray) which I'm passing to the method is not in the same order as *battingLineUpTemp... Why is my code refusing to let me change the order of this NSMutableOrderedSet!? Is it CoreData being a massive pain in the arse once again?

Edit 1 I have also made sure that the object that I am replacing and the one which it is replacing are different by NSLogging within the for loop... the NSMutableOrderedSet is simply refusing to be rearranged!

SimonThumper,

An ordered set has many uses, but it is primarily a mechanism to preserve insertion order. As you want to change your lineup order, I suggest you actually add a property to contain the position in the lineup and then sort on that order. (You could also use this as a property to easily pull the lineup out of the roster by checking for non-zero values in the lineup property.)

Andrew