How far out can you go in Minecraft?

As a lot of people know the farthest coordinate you can get to to in Minecraft is 29,999,999 blocks in both the x and z coordinates. Or is it? Recently I've been playing around with it and if you get on a horse it is possible to get past that mark. At first I thought it was right around 30,000,010ish when you get teleported back to 29,999,999 but then I realized that was only when I either went up or down or I hit a piece of grass. So I went to a super flat world and just as I had thought, I rode right past the 30,000,010 block mark I had gotten to previously. But then something happened, the word just stopped loading at 30,000,175 blocks, but something interesting the sides of the block didn't load either, the whole world was just one flat infinitely thin plane, something I thought was quite cool. I tried everything I could think of to get past 30,000,175 but nothing works, when you try to go to 30,000,176 the horse disappears but I'm still riding it but I can't move not even back to what is loaded and your camera position is stuck and you can't get off the horse. You either have to leave and rejoin your world or /kill @ e[type:horse] Also when I relogged the distance I could go when down to 30,000,078! I don't know why. Does anyone have any ideas of either how to get past this without hacked clients? Or any info on if this is actually the end of the world? I also tried to make a world with a top layer of TNT and blow it up but for some reason the explosions stopped around 30,000,069 blocks, why would they stop and not go to the end of the world?