I was making a rig for the TNT carts where a piston replaces the powered rails with the activator rails. I put 4 carts in and then they randomly exploded and then my game crashed. I then tried to recreate the bug, but i couldn't. However when i put the cart on a three long power rail line that was powered from the middle underneath by a red stone torch, the TNT cart exploded without a countdown animation. You can see a video here: http://youtu.be/XuPKDg_ALX8
0%, The video is still uploading so it might not be ready.
Linked issues
Comments 2
Duplicate of MC-6770.
There is also two other things. The minecart with TNT does not pass through a portal, with or without rails in the nether, but it does disappear when it reaches the portal. The other might not be added yet, or could be a bug, the dispenser does not place a TNTcart on the rails when powered, just shoots it out as an item.