Thanks for the playthrough! I actually wasn't able to fully test explosive rounds, but i knew the cost for them would be pretty high so it would only be achievable in the last levels unless you get lucky! I was just throwing guns into the game just for fun, which is where the 50 cal came from ;)
The pistol i felt was a good balance gun, I went back and forth on whether to require the pistol to be a 2-shot kill for the mini-bots or 1. In the end, I had to scale the enemy spawns down a bit. I found robocop, and doombot is super OP. If you don't kill the robocop fast enough, you will quickly be swarmed.