The Winchester SX3 is the only mounting system besides the Remingtons that require a stock modification. Winchester has changed their stock to receiver configuration since we designed this mount and now requires some work. This is just a real quick run through of the necessary modification.
This is what your stock may look like. Winchester has changed the stock several times over the last few years so it may be slightly different. It makes no difference as the modification will be the same.
When you place the mount on the stock you will notice there is excess material. Mark the outline of the mount. This will be your guide when you start removing that raised material. You can see in the picture above what it should look like after you've marked it.
Slowly remove the excess material with a rotary tool and cutting wheel.
You should have something that looks like this when you are done.
You can now continue with the mounting process as usual.