Older mags have a hole in the floorplate as you've likely seen. Using it to push on the spring's nose piece is simple and the floorplate slides off. Newer magazines are made the same, but S&W in their infinite wisdom omitted the external hole in the floorplate. There's a blind hole inside for the nosepiece to drop into, you just can't see it from the outside.
So, how does one depress the nosepiece and get the floorplate off? Just use something like a dental pick or small hook to reach inside the magazine and pull the spring away from the floorplate. The same nosepiece is in there and all you need to do is get it separated from the floorplate. The floorplate will slide off like it does with older magazines. Reassembly is about the same as with older magazines, but it can be tricky to get the nosepiece settled in the blind hole. Again, why S&W did this baffles me.
If not - break down and use the Remoil - great for what you are doing.
