I have been reloading some 300wsm Winchester Nickel cases with a redding S type neck die and a redding body die.

The cases are very stiff to chamber any ideas why this is people?

I'll venture a guess. The neck die reduces the neck and the body die reduces the body. What pushes the shoulder back? That's probably where your interference is coming from. And, I don't think it has anything to do with the cartridge or the nickel case.

I think that the WSM cartridges often give that kind of problem; I had myself some issues with my Tikka T3 cal. 270 WSM with both Lee and, lately, RCBS FL dies; reloaded ammos were difficult to chamber. I had to slightly hone the RCBS shell holder (0.03 mm.) to push back the shoulder and be able to easily chamber reloaded ammos. IMO neck sizers are possibly not well suited for the WSM cartridges.

Thanks the redding body die sould bumo the shoulder but doesnt seem to be doing it I did wonder if anyone else was having similar problems.

Now shall I polish the shell holder or the body die :-)

As I learned here, it's easier to hone the shell holder; I did it in 2-3 minutes with a sheet of 220 grit sandpaper lent on a flat surface.

I also had this problem. I took the advice of some of the people on here and barely grinded on the shell holder. After I did this I have not had a problem since. I had the problem with the 270 wsm. You are not the first person to post this problem on here and surely will not be the last. I'd say that the die companies will eventually solve this problem with the wsm cartridges.

Thanks guys I was begining to think there was something wrong with either what I was doing or the rifle

I need a "ground off" shellholder for a couple of magnums I load for. The top of the shellholder has nothing to do with any part of the reloading process so it doesn't have to be a super detailed problem. I took mine and held it with a vise grip against the side of a grinding wheel. Lightly buzzed off .010" and screwed the die down slightly. Problem solved.
Re the wsm..the more you shoot the brass the more brittle it gets and springs back more. So...if you start feeling bolt tension on the 2nd or 3rd reloading you may have to turn the die in again on the 5th or 6th. Don't know how many are loading past 6 loadings. Also annealing can fix the problem.