[Jack]

"My idea is that the hollow point gets damaged somehow and closed in some. There for nothing tears open on impact and the monolitic bullet does not expand. However with a conventional lead filled bullet the lead is weak underneath and the bullet expands anyway if if it had a hollow point which few do. "
I don't have enough real world game experience with Barnes bullets to answer that re Barnes bullets.
But, I have shot a lot of lead core hollow point varmint bullets thru woodchucks, foxes, etc. I can tell you that some hollow point varmint bullets have had the hollow tip close. When that happened, the bullet did NOT expand- it penciled thru.
I wasn't sure that was what was going on until I dug a few out of the ground- not fun, but illuminating.
Happened to me with 22 caliber match HP's- and often enough not to be a fluke.
I will say, it happened quite a few years ago, and my only experience with the hollow points closing was with match bullets.