Penetration versus Expansion

R

roy reali

New member
A couple of other current threads made me decide to start this one. My basic question is this, which factor is more important when shooting bullets into animals, expansion or penetration? Does the species that is being shot affect which is more critical? If you had to loose some of one to gain some of the other, which would you choose?

I am not a ballistician or even the most experienced hunter in the world. However, I think that penetration is more important. Don't get me wrong, I understand that expanding bullets should cause larger wounds, thus more tissue damage and quicker death. That is what us hunters really want, a quick and merciful end to an animals life.

Hearts, lungs, even brains are not located near the surface of most animals. If a bullet doesn't reach a vital, all the mushrooming in the world is worthless. Most of my hunting experience is with bird hunting. Small shotgun pellets don't exactly expand. I do like to explore the interanl damage done by them when I am field dressing a bird, espically if the bird died before hitting the ground. On those instant dead birds, I have found the one or more pellets had reached the lung or heart, no expansion of the pellet. In fact, if the projectile was cleaned it could be used again.

I realize that bird anatomy is very different then deer or bear anatomy. But shouldn't the principle be similar. If a bullet, expanded or not, cuts through an animal's heart, the animal soon expires. If a bullet expands but doesn't reach a vital, the animal will suffer some.

So, where do you guys stand on this? I want to hear form hunters that have more experience then me, which is probably most of you.
 
My answer is yes to both. The expansion causes disruption in the organs on chest shots. The penetration causes increased blood loss, disabling the animal quicker.
 
I want both as well, I want a bullet that will at least double its frontal diameter and will penetrate to the off side. Preferably I'd like it to penetrate far enough that a bullet recovery is impossible. Most of my rifles don't need a premium bullet to do this, however when I do I like a Partition to get the job done. Even if I do loose the frontal portion of the bullet it does the initial damage, the shank will do the rest and get the penetration I want.
 
Placement is critical - of course, but the deer and hogs I've shot and had to trail afterward, the shorter trails tend to be those with both an entry and exit. With animals, I believe rapid blood loss is key unless you're lucky enough to destroy the heart or hit the CNS.
 
I'll chime in with a confident 'it depends'. Reaching the vitals is my first priority, expansion a close second. A bullet that expands to 2x origional diamater won't do any harm if it barely breaks the skin.
With light boned, thin skinned game, almost any common hunting load will provide adequate penatration, so I pay more attention to expansion.
For heavier-built critters (bear and hogs in my case) penatration is critical. Dense mucsle and heavy bone structure makes getting to the vitals a challange.
Choose the load for the game
 
Yes to both

One of my mentors is a gentleman who has been reloading for 47 years and is also a former Marine Corp sniper (Veitnam). He is also avid deer hunter who often takes shots in the high 200"s to low 300"s yard range. He knows his stuff....no debate on this point. Here is his definition of the perfect bullet. A bullet should enter the animal and begin to break up in the chest area. The follow through of the fragments should retain just enough energy to lodge in the hide of the opposite side. Expend ALL of the bullets energy in the animal. Provided you did your job with shot placement, there will be no need to track the animal. He believes that there is entirely too much hype when it comes to weight retention....bullet company propaganda. Now if it is Old Griz you're talking about, I want penetration first.
 
In a perfect world, the bullet would expand as much as possible and impart 100% of it's energy into the animal, just barely falling out the other side. Exit wounds can be important, particularly from a tree stand. Given a choice, I'd take a little extra penetration and a little less expansion. Expansion is not terribly important if your bullet hits what it's supposed to hit but a bullet that doesn't expand much OR exit the opposite side could be a real problem... not for killing but for recovery.
 
Whatever happens ... It has to hit vitals.

As for the rest ... Depends, depends, depends.

I like the idea of a bullet expending all of its energy in an animal, but I also like exit wounds. I've seen both work equally well - on different types of game (sometimes, with the same bullet).

And, sometimes its not just about terminal performance. It's also about getting the projectile into the animal (in my neck of the woods).

For deer and elk, I often end up in areas with thick growth. The other hunters avoid it, which makes it that much nicer for me - and a safe-haven for the animals. But, it means a long shot is going to be 50 yards - if that. Anything over 10 yards will probably have some twigs, sticks, leaves, or other minor obstructions, too.

I haven't settled on dedicated deer loads (haven't seen a legal deer on a deer hunt in 10+ years). However, I have adopted the old "Heavy and Slow" philosophy for Elk. My loads use old-school cup-and-core bullets that are heavy-for-caliber, and aren't going to break any speed records. They will, however, absorb a few twig impacts without being upset too much; and the 'heavy and slow' should give good penetration, while the classic bullet design gives controlled expansion at the low velocities.

Two examples of the "heavy and slow" loads are: A 215gr Woodleigh Weld-Core RN for my M38 Mosin (2,000 fps) and my brother's Type 99 7.7 Jap (2,100 fps). And a 220gr Hornady RN for my brother's .30-40 Krag, at about 1,700 fps. They're long, heavy bullets with good reputations - when used properly.

For Antelope, I'm still undecided. They're such a lightly-built animal... it's hard to stick to one idea. While I'm thoroughly impressed with the 'grenade and penetrate' performance of .277" 140gr Ballistic Tips; they only work when you get a broadside shot. I have had great luck with good ol' 130gr Core-Lokts, but a few rather disappointing outcomes, as well. Something like the Partition sounds fine - but I want Antelope to have that grenade go off in their chest. They're too fast, too small, and too sneaky to hope for a deep-penetrator to cause them to bleed out.

This year, I'm going to try for the best of both worlds, with some Swift Scirocco IIs. We'll see how that works out...


In summary:
You always need penetration and expansion. But... sometimes you need more of one than the other.
Know the terrain. Know the animal. Know the rifle. Know the load. Know the limits.
 
FrankenMauser

You always need penetration and expansion. But... sometimes you need more of one than the other.
Know the terrain. Know the animal. Know the rifle. Know the load. Know the limits.
Click to expand...
Very well said and you call yourself a thread killer.
 
My answer is, "it depends".

If I'm shooting a large caliber firearm, then expansion isn't as important. If I'm shooting a small bore firearm, then expansion becomes critical on larger animals; as long as there is enough penetration to reach and pass through the intended vitals.

The laws of physic's demand that expansion reduces penetration.

Now, if you're shooting a deer with a 400 gr bullet from a 45/70, then expansion and penetration are likely irrelevant. It's going to shoot completely through the deer, no matter whether it expands or not. It's also going to leave a .457" or larger hole in the animal, even if it doesn't expand.

On the other hand, if you're trying to penetrate 3 feet of bone to reach the brain of an elephant, using a packable, shoulder mounted rifle, then you really don't want that bullet to expand. You need penetration, and expansion will reduce penetration.

There's good reason behind the fact that large bore solids are very popular with those who hunt large, dangerous game in Africa. They need penetration, and a big hole. The bullet doesn't need to expand, because it's already "big enough".

There's also good reason behind the fact that small bore, expanding bullets are very popular with those who hunt large, not-so-dangerous game in North America. The game is smaller, poses far less risk to the shooter, and the bullets kill well without excessive recoil.

Handgun hunters have long known that you can't depend on expansion of smaller bore projectiles at the velocities reached with short barreled handguns for killing larger game. You simply can't get enough velocity from such a firearm for dependable expansion, and still have enough penetration to reach vital organs dependably. That's why big bore handguns, shooting heavy-for-caliber hard cast bullets are so popular with these shooters. Smaller bore handguns, when loaded with expanding type bullets, simply won't penetrate deep enough.

This is not a "one-size-fits-all" equasion. There are simply too many variables, and not enough constants in the question for a solid answer.

Daryl
 
Penetration

The fact of the matter is, penetration can kill without expansion but not the other way around. This being said, expansion is still a critical thing to have if you want quick results.

GAR
 
It's all a compromise, and you get to decide which compromise you choose.

Ideally, a bullet should penetrate. If it does not, it will not cause the damage to blood vessels and organs that lead to rapid death. Large, heavy bullets work best for penetrating, but fewer and fewer people like shooting heavy bullets because it means heavy recoil, so we shoot smaller caliber bullets and hope they will expand and cause heavy blood loss. Expansion is only important in that it increases the frontal diameter of the bullet, causing a larger wound to leak more blood.

Solids penetrate more deeply, many animals have been shot with solids, especially dangerous game. One issue with solid hunting bullets is that since they are often round nose or flat point bullets, they have poor trajectories. Since we all want flat trajectories, we want pointed bullets, a profile that will allow solids to zip right through an animal without causing immediately debilitating injuries even though it will likely die later. Hence, expanding bullets. Pointed so it flies well, but when it hits it turns blunt and transfers a lot of its energy. A compromise to get as many advantages of penetration and trajectory, without too many of the disadvantages of expansion and profile.
 
"Expend ALL of the bullets energy in the animal"

Energy doesn't kill anything. It's a worthless number used as a marketing tool.

It is tissue damage and blood loss that kills, not energy. If energy killed, then bows & arrows wouldn't kill them. This discussion ranks right up there with one about "knockdown power".

In a perfect world you would want a bullet that would hit & expand to 2x its diameter and still go clean through the animal. I always want total penetration because 2 holes are better than one. One lets cold air in, the other lets blood out.

I always use a caliber/bullet that I know will deliver total penetration on the animal I am after at the distances I am likely to encounter. If it does this and expands, great. If it does this and does not expand, who cares. I still have a hole clean through the vitals/bones.
 
I am no expert on either. All I know is what I seen when I shot something, with factory or my reloads. I like a bullet most of the time to be able to make a pass thru, and have good expansion at the same time. Sometimes it is hard to find that correct combo. A lot goes into what you are hunting. I like to see the drop on the spot which is what happens most of the time, but when it does not it's nice to have a serious blood trail that does not go very far. I guess that were the expansion comes in to play. Able to stay together but make a good expansion, and keep on a going.
 
expansion is great, but you have to have the necessary penetration for that expansion to do it's job. I would vote that penetration is most important, you can kill an animal with non expanding ammo if you penetrate and disrupt the correct vitals. A bullrt that blows up on the shoulder of an animal is useless. It doesn't bother me a bit paying the few extra bucks for good controlled expansion ammo.
 
I shot a whitetail doe broadside through both lungs with a 300 WBY Mag. The bullet zipped through, never expanded and the doe went 300 yards with no blood trail until her lungs filled up to where the hole was and wet the fur to the point it started to drip. Luckily I could see her most of the way or I may have never found her.

Same rifle, same load, I shot a whitetail buck, body slammed the deer and blew stuff about 20 yards in to the bushes.

One without the other is bad.
 
The answer is both, but if pressed, I want penetration first. Well, actually second since shot placement is first.

After I've put the shot where I want it, I want it to reach the vitals and punch through them. Along the way though, if the bullet can expand (or even break apart a bit) that is okay by me too.
 
After I've put the shot where I want it, I want it to reach the vitals and punch through them. Along the way though, if the bullet can expand (or even break apart a bit) that is okay by me too.
Click to expand...

Know the terrain. Know the animal. Know the rifle. Know the load. Know the limits.
Click to expand...

Pretty much sums it up......If Ican have only one of the two, with good shot placement I'll take penetration. All the energy and expansion in the world with no penetration equals nasty flesh wounds or fatal wounds that take some time and cause undo suffering and lingering deaths.
 
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