Bullet Frangibility and Fragmentation

In his 1966 novel, Use Enough Gun, Robert Ruark wrote about the .220 Swift...

"The pig was trotting, his antenna-tail straight up. I held the little hopped-up .22 on his buxom backside and it felt steady. I squeezed and peeled a ham off his right hip. He let out a squeal and went into the bush, leaving blood behing him. We tracked him and we never found him and I looked sadly at the .220 Swift and sadly at the boys and sadly at Selby.

'You can blame the gun on this one,' Harry said. 'The bullet broke up on the outside of the pig. Didn't penetrate. I have read a lot about these speedy little guns, but it seems to me they wreck the little stuff and just savage the bigger stuff..."

Ruark and Harry Selby were absolutely correct. The .220 Swift was not designed as a big game cartridge but rather as a varmint round. And with varmints and fur-bearers, frangibility is a good thing. Still the debate rages on, with some arguing that even a stout blade of grass will cause these bullets to explode. The potential problem of course, is that the bullet may fragment on the hide of a coyote and not only ruin its fur, but fail to kill the animal cleanly.

Is this true?

To find out, I designed a little experiment. I used two pieces of heavy corrugated cardboard as targets placed one behind the other (the targets were seperated by about 18") at a distance of only 50 yards from the muzzle of my .220 Swift. I was shooting 40 grain Combined Technology Ballistic-tip bullets at a velocity of nearly 4300 fps. If a bullet was ever going to fragment prematurely this should be the day!

The result was conclusive but anti-climactic. In both targets there appeared clean .220 caliber bullet holes, each as neat as the other. There was no indication of early fragmentation or erratic flight (no keyhole "yaw" shape) in the targets (note: five rounds were fired for this test, each giving identical results).
(note: applying any of these suggestions is done completely at your own risk)