If .50 Caliber isn't enough...
 

Maybe a .95 rifle?

The Guys from Knight Rifles Shoot the .950 JDJ, Extended Version - YouTube

That just makes me smile.

good for plinkin' and rodent killin'!

I know it sounds sick, but high speed footage of that hitting something like a squirrel would be pretty damn interesting!

There's an outfit outwest that makes man-portable (and I use that term loosely) 20mm rifles...

Anzio Ironworks, maker of the 20mm rifle.

http://www.anzioironworks.com/images...atangle-FP.jpg

That is awesome!

Some curiosity questions:

- Why did that one guy tell the last shooter to lock (the bolt) slowly?

- In that configuration, what could you use it for? Is it more an experimentation/research platform or was it ever marketed with a specific purpose?

Not really. Large, slow moving projectiles are pretty unimpressive when they hit something. You could throw a baseball at a squirrel and get about the same affect. Up the velocity (like double it) and employ a very frangible projectile, and the story changes quite dramatically.