Therno, it's quite a simple job to fit a new butt stock to your No4 rifle, just a bit of patience really. Just take your time- it's much easier to remove wood than to try sticking it back on. You should find that your L marked stock is about 1'' longer than the stock on your gun which you state is marked S. There is a about a half inch difference between the short normal and long stock. I believe that the rare bantam stock is 1'' shorter than the S marked stock although I'm not certain on this and it may only be half inch shorter which would seem logical???