While making an arrow/lava pitfall trap, I had a dispenser wired to a very fast clock (I used a rapid pulsar for this, but any fast clock works), facing a wall made of TNT (because why not) and lava under it, finishing the trap with bedrock under that. When the arrows hit the TNT, they began to fall off,seemingly at random, and they fall through the lava, igniting the arrow. When the arrow hits any block, the block changes to TNT, which is then primed by the burning arrow. This detonates and leaves a hole, where the process starts over. My theory is that the arrow "remembers" that it is in TNT, even though it is not. When it hits a block, the game the arrow 'tells' the game that that block is TNT, which it then changes. If you have the materials, this is easily replicated in survival. I verified that this works in multiplayer. I also have moved the setup into a Superflat world so that you can better understand what I did, and I have provided a map and a screenshot for you to use if needed.