This topic is subjective, depending on alloy, profile, velocity, etc..., yet, it is important for those who may not be initiated in hunting with lead arena, or have little experience. I read all the time that a (place caliber of boolit here) doesn't need to expand because it is already xx/xx of an inch already. Or that all the buffalo were kilt with such and such, and once you stroke the trigger the quarry doesn't stand a chance because the lightning of Thor will smote it in it's tracks, DRT. To accept this line of thinking will cause the novice lead boolit hunter to question their choice of projectile right quick once the trigger is pulled. Let me share an example:
This past Saturday I was beating myself up with the 45/70, getting ready for the upcoming deer season. To end the session I finished sighting in a light load in the 35 Whelen using 7 grains of Bullseye and a hard cast 190 grain FN PC bullet at 100 yards. Such fun seeing the holes open the paper within an inch and a half. These are flying between 1,000 and 1,100 FPS. Not fast and no expansion, but with a good meplat to cut a path through paper, or possibly tissue.
Then my friend texted to remind me that her barn floor is being destroyed by a family of groundhogs and she needs help. With the Whelen shooting so good I drove straight over. At 30 yards the cross hairs were centered half way up the torso on a prone hog and I let rip. My, that whistle pig jumped nearly 2' up and took off into the raggity barn ten steps away as if not touched. No spoor was found nor was the varmint in the interior of the barn. I surmised it made it down the hole or passed under a piece of equipment. The next day I popped an other with the 17HMR at the same range, dropping dead where it rolled off the rocks. A fast, small bullet has different characteristics.
Today I drove by and noticed two buzzards at the barn, which wasn't where I disposed of the HMR kill. Walking up to the barn was the first groundhog's carcass, having been pulled out of the barn by some unknown animal and being picked at by the birds. The 35 caliber boolit passed crosswise through the torso, killing it but allowing a run away from the scene of the crime before succumbing to its wounds.
This reminds me of over three decades ago when I first started shooting and hunting with 50 caliber muzzleloaders, black powder and pure lead conical slugs at 1,180 fps. I would sneak up on groundhogs, drill them through the chest only to have them run to their holes with a half inch hole where it shouldn't be for long life. How can such a small creature, though dead on its feet run off when the lungs and heart have been demolished? I began to equate heavy, wide nose lead slugs with broadheads, they cause a big wound, if placed correctly does kill the creature quickly but probably not at the spot of impact. Bang/Flops were and are not to be counted on, in my considerable experience with this type of projectile. Sure they can happen, but don't be surprised when they don't, accept it as it comes.
If a groundhog can absorb a piece of lead 1/3rd, or even 1/2 of an inch and run off, think of what deer size game will do. Yes, that's exactly what they normally do. Yet, don't let that deter your hope of making meat. Placed in the right spot that animal is down at the end of a fast sprint, awaiting to be field dressed and hauled off to be butchered. The faster the lead boolit is launched with a good flat nose or expandable soft lead at the front the better, IMHO. But get used to blood trailing with dogged determination. That can be a sport in and of its self. I share this to hopefully give those new to this type of hunting a better understanding, not to give up once the shot is made and the animal's reaction doesn't give the slightest hint that you are successful in executing a perfect shot. Stay at the track and be rewarded with the prize at the end of the trail. Happy Hunting this Fall.
ChristopherO