The last couple I have shot with a lead jacket bullet had only one entrance would because the bullet hit a bone and exploded on the inside on the animal. One was a antelope at 317 yards COM, 165g Hornady SST bullet went in below the neck and exploded on the spine near the tenderloin. Also shot a deer this January with my ML shooting a sabot 250 g Hornady SST into the chest, hit a rib, the bullet exploded, part of the jacket was recovered in the rear haunch.
I'm about ready to give up on Hornady SST bullets, they shoot good but I'm not getting the results that I want when hunting.
What velocity? I use Sierra Gamekings in my 6.5x55. Gamekings are supposed to be soft and weak according to Internet Lore, but I only drive them to 2500fps. Even on close shots (50yds and below), they hold up just fine. I shot a doe at 50yds, punching through a rib and the offside leg bone, and had complete penetration. I shot a large buck at 25yds. The first shot, through the neck, didn't hit any bones, but was through and through. The 2nd shot, through the back and out the sternum (was putting him down from my tree stand after the neck shot only paralyzed him) was also a fully penetrating shot.
I think the key is not driving them too hard. Other "internet hunters" show pics of the Gamekings exploding and ruining meat, but they've held up fine for me. Of course, I'm shooting them from a 6.5x55 and those others are shooting them from 264winmags and other high velocity 6.5s.
Chris