If you are having trouble getting your rocks to make it to the other end you have a couple of options.
Install your rings closer together. Whatever distance the rocks travel naturally is a good guideline for how long to make your rink. See "how long should I make my ice rink" in this FAQ.
Reduce the friction between the rocks and the ice surface by pebbling the ice. See this link for more information about pebbling outdoor ice and when it might be necessary.
Use a delivery stick like this one to "throw" the rocks from a standing position. You'll be able to push them much harder with a standing delivery over a sliding delivery.