I guess I need to change my reply. I have too had 45 acp knock a hog over when shot in the shield, but not take it down. It took a second head shot to dispatch it. I was going by my personal experience, and when I go for hogs with a rifle, the smallest I use is a 30-06. And I have not used it in years. All the hogs Ive shot with a rifle in the last 7 years have been with my 300 wby.My 300 has no problem problem punching the shield, and everything else for that matter. But yea, I could see some calibers having a difficult timepunching the shield.