I know that this isn't scientific proof of anything, and your barrel might make different patterns, but I believe this IS pertinent data.
Ever try the same experiment with 00 buck?
My version was a computer case packed with computer components at 8-10 feet. Just a standard mini-tower, shot from the bottom so that it was going straight into sheet metal. Consider it ballistic gelatin calibrated for robot.
Birdshot made a dent.
00 buckshot made 9 or so [smaller] dents.
9mm ball made a hole but the bullet didn't go far.
.223 made a hole and the bullet did quite a bit of damage to the case contents.
7.62x55R made bigger holes but not enough bigger. Some of the bullets also left the other side of the case.
12ga slugs made a big hole and caused the most internal damage.
My scientific conclusion: Shot, including buckshot, is insufficient to stop the robot overlords from enslaving humanity. When faced with a machine uprising insist on slugs or, if cost is a factor, .223.
NOTE: if you decide to try your own experiments, first think about where the lead is going to go if it doesn't stop in the target or backstop (think mirror) and do try to make sure there are no robot spies watching....
Extending this to humans: birdshot is firmly in the "I don't wanna be hit by any thanks" catagory for me... and it has its place in home defense... but shot is at best equivalent to a bunch of pistol-caliber handgun hits and there is a real lower limit. Slugs are in a class of their own. Lead BB shot is going to be like being hit with, what, 50-60 .177 pellet gun rounds going way faster than they'll ever go out of a pellet gun. I've been shot with a .20 cal pellet gun (that didn't push pellets at anything like 1300fps) and it ain't fun. 60, in a 1-2" circle, with over 4x the energy (over twice the velocity)? Count me out!