First time posting here. Hope it goes good. My question is does bullet diameter really make a bullet that much more lethal? What makes the most damage to the animals lungs? Is it the energy? The way the bullet expands? How fast the bullet expands? The size of the hole a bullet pokes through the animal? Does this make sense? I hear it offten that a 30 cal is better because of the frontal diameter. I guess my question is does the diameter really make the biggest difference or is it the speed or bullet or other things like that? I understand the idea of the bullet expanding double the original diameter and a 30 cal being bigger than say a 7mm but does is that what’s making wound Chanel?
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I’d love to see what others chime in on this topic. I mean, just logically thinking through it as a scale from a BB to a 50 BMG, there’s a point where enough is enough and you are getting diminishing returns.
The 22 Creedmoor and Rokslide thread about the guy who hunts with a .223 are really challenging my own thoughts lately of how much is sufficient.
Seeing more and more evidence via backfire and other sources that recoil matters a lot in being able to shoot well. That being said, I also do not want to wound game, and want something that will kill the deer/elk 9 times out of 10 with a typical shot radius. (I would say 10/10, but then think about how some people survived the nuclear bomb and sometimes it’s just an act of god. Even if you do everything right, an animal may not die).
I don’t have the answer. I don’t know if it’s a .223, .224, .243, .270, .284, or even .308 that’s enough to get the job done 9 out of 10 times while also minimizing any recoil.
*I get that shot placement is everything. A 22 LR could be used with a perfectly places shot, but would be curious to see what others say would do the job with an average shot radius.
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I think speed and energy are more important that diameter, but diameter is important. Where diamater really seems to make its case is in the less than ideal or completely not ideal shot angle, like quartering away. I would much rather have a 30 cal over a 6.5mm in that situation.
Accuracy trumps all.
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A difference? Yes. Big difference? No idea. And Trust me, if you go looking on the internet you will find every opinion Under the Sun on this.
I know several elk Hunters who will not carry anything less than a 28, or even 30, caliber rifle into the elk woods. Yet, Jim just posted a video with two of his boys each shooting a good elk with a 26 caliber bullet. Don’t hunt elk myself, at least yet so no opinion personally.
Of course a lot depends upon magnitude of change. Are we talking about going from a 0.277 to a 0.284 caliber, versus a 0.243 to a 0.338? Also, same for velocity. Are we talking 2800 ft per second to 3000, or 2400 ft per second to 3400 ft per second?
There are a number of calculators out there for wounding/killing effectiveness of a bullet. Of course they’re all designed by different men and therefore each places priority different aspects. The above mentioned elk Hunters I know use one that does Place heavy emphasis on bullet diameter. Others Place more emphasis on speed, sectional density, or something else.
Then of course, in my opinion at least, the big thing is what wounding mechanism is the specific bullet trying to do? I constantly debate between deep penetrators like a copper bullet versus rapid expanders like a Berger bullet.
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A agree largely with @mwoolsey and @BEN with a few additional points. I would say comparative lethality does not necessarily come down to one factor. I think bullet diameter, weight, velocity, terminal ballistics, practical accuracy (shot placement) are all factors. A couple of general thoughts. Assuming you can shoot one as well as the other, a larger diameter bullet that weighs more and has equal or higher velocity that expands properly will deliver more energy to the target. That is physics. However, we also know shot placement is critical. You can have a heavy, fast projectile, but if you hit the guts, well, not a good outcome. We also know Karamojo Bell took elephant with the 7x57. So big diameter, heavy, fast, is not everything.
Jim’s recent explorations of caliber, rifle weight, and recoil have been illuminating. From this we see that harder recoiling rifles are generally just more difficult to shoot accurately. You can learn to do it with the investment of practice, but I’m not sure how many shoot the rounds required to get good with a heavy recoiling rifle. I am an RSO at my local range and have gotten to know the regulars. You can tell the difference in their targets.
I think the point about how much is enough also bears consideration. I think we would agree that while a 50 BMG will kill any game, it is more than is needed. As mentioned, you can kill an animal with a 22lr if your shot is perfect, but I prefer a little margin. There are certainly proponents of smaller caliber, lighter recoiling rifles that emphasize shot placement. Then, of course, there are also proponents of large, heavy magnums for the hard hitting, bone breaking knock down power. For my thinking at least, the intended quarry bears consideration. For deer sized game I’m totally sold that the various 6mm and 6.5 mm cartridges are enough. I’m even open to the 22 Creeedmoor for game of that size. For larger game, I favor a bigger, heavier round. I am concerned about the ability of light projectiles to penetrate heavy muscle and bone. In the end, we all have to decide which camp we’re in, but in general, I think the best choice is the biggest caliber you can still shoot well. And regardless, put in regular time practicing.
I think caliber matters more than its given credit. When I look at an expanded 308 bullet vs a 6.5mm, it’s impressive. 20% larger cutting surface makes a big difference in my mind.
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So is that extra 20% making just a 20% bigger hole? Or is that 20% causing more ballistic damage? If that makes sense or is the right word?
It’s certainly causing a 20% bigger hole, but I also have to think that extends out to the tops and tears outside the hole that are just being disturbed more.
If my math is right, a 20% increase in diameter leads to a 44% increase in the size of the wound tract volume. That’s assuming penetration is equal.
Oh, and the elk Hunters I mentioned above who won’t shoot an elk with anything less than a 28 or 30 caliber, talk about " Authority" of a larger caliber bullet. According to them, if you actually watch the elk react to a gunshot from a fast moving 6.5 mm projectile versus a slower moving 308 projectile, the elk reacts much more to the larger projectile when it is hit.
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I would argue that a 20% bigger hole is more ballistic damage.
Also not just hole size. The frontal area is a square function the bullet radius. And as that expands it increases more. And that larger circle has more inertia which a function of the bullet mass. Inertia is a resistance to change in motion. More mass - more inertia - more the bullet wants to keep moving forward - more penetration through bone and tissues reaching into vitals and keep
going through. A 22 will not give you that like a 30 cal. not matter how fast you shoot it.
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Thanks for all the comments! Lots of good info.
I think that the game you are hunting is the key factor with what size caliber to use. With deer and smaller game everything from 6mm to 308 will kill the animal relatively the same… very dead (with a good shot). So save the recoil and shoot smaller calibers on deer size game… But with larger and thicker skinned game a bigger bullet makes a difference. Yes you can kill elk with a 6.5… but most of the time you will get a cleaner, faster, more forgiving kill with a 7mm or .308 or larger.
Lets not forget design and construction. I would use a correctly designed and constructed projectile of smaller diameter over a larger projectile that would fall apart on impact. I have experienced this first hand.
Also what about FT scott tumble on impact? If it does what it claims a .22 tui might do more damage than even a well constructed. 30 cal bonded etc…
I not not think so. Back to inertia and penetration. A tumbling 22 does not have the mass to keep on going through. It will stop faster even if tumbling than a 30 cal 3-4 times its weight.
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This conversation is making me question my 6.5 PRC purchase. 
. It sure does shoot nice though. Rifle season is almost upon us here in WI so I guess we will soon see.
@ ross.
They claim it’s barrier blind meaning it penetrates until it hits vital organs and then dumps energy by means of " tumbling "
They have some fairly impressive videos of dropping large black bears with pistol calibers etc.
6.5 prc is basically the same as a 270 so you’re good as 270 is certainly a very good whitetail deer cartridge.
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We’ve shot several deer between 500-650 with a 6.5 creedmore and the damage it does at that range is crazy. I can’t imagine any animal with a wound chanell like that making it that far. I just don’t see a 308 doing that much more damage than that. Not enough to say the 30 cal is that much better.
You’ll love the 6.5 prc. We just killed an elk with one a couple weeks ago and it worked great at long range. 600+