My best so far after a couple playings:
Final Score: 67282
Edit: Okay. Apparently a trick is to find somewhere that ricochets the BB around the fence. Bounces pile up and so does the score. I found one such magical place and managed several shots of 132 bounces. Several.
Final Score: 4026608
The Final Score is actually a little off, though. Unfortunately the score seems to be stuck at seven places and just rotates through again, not actually adding up into the tens and hundreds of millions. I watched my score go from 3 million-some to 8 million-some to 6 million-some to 4 million-some and a bunch of other scores, too. So I’m not convinced any final score is an accurate measuring tool. The bounces seem to be accurate, though.