Home Forums Hunting & Shooting Ask The Gunwriters Mid-August column: How Hunting Bullets Expand

HOW RIFLE BULLETS EXPAND

Many hunters believe expanding hunting bullets vary considerably in how quickly they “mushroom,” due to how the bullet’s constructed. In reality, most start to open immediately upon hitting an animal, and how long it takes for the bullet to fully expand also doesn’t vary much (though there’s an exception we’ll examine later).

Unless they don’t open up at all, most expanding bullets fully mushroom within one to 1.5 times their own length. Most “deer” bullets are around an inch long, so are fully expanded by the time they penetrate an inch or so, but even the heaviest expanding bullets are only rarely as long as 1-1/2 inches. This means the deepest they penetrate before full expansion is around two inches. All of this has been demonstrated many times both in test media and game, even if the bullet’s “hardness” varies, but two newer kinds of media have revealed some very interesting aspects of bullet expansion.

One is clear ballistic gelatin, which when combined with modern high-speed digital photography allows us to actually watch expansion as a bullet enters a block of gelatin. Some bullet companies now include slow-motion videos on their websites.

The other was the Test Tube, made of a wax somewhat harder than ballistic gelatin. (It’s now out of production—though I still have a bunch.) The wax retained the shape of the wound channel, and when sectioned provided an interesting comparison without high-speed digital video equipment. Here’s a photo of two Test Tubes, the top tube shot with a Nosler Partition and the bottom tube with a Barnes TSX:


Note that the initial, wide portion of the Partition’s wound channel is thicker and shorter than with the Barnes TSX. This occurs because the Nosler initially expands wider, due to its front lead core, then loses some of the core. The Barnes doesn’t expand as widely, the reason the initial wound channel isn’t as wide, but in test media the Barnes typically doesn’t lose any weight. As a result the wound channel remains about the same size as the bullet continues to penetrate, narrowing after the bullet starts to slow down considerably.

With both bullets, however, the initial wound channel starts to widen as soon as each bullet enters the Test Tube. This also occurs in high-speed videos—and animals. On an African safari I shot a male impala with a 286-grain Nosler Partition from my 9.3x62. The ram stood angling almost directly away at a little over 100 yards, and the bullet angled steeply into the ribs, exiting the front of the chest. The beginning of the bullet’s expansion can be plainly seen not just on the ribs but the skin:


The lighter “tail” to the left of the entrance hole was made as the side of the bullet skidded along the hide. When it dug in a little deeper, the soft lead point encountered the hide, and the bullet immediately started to expand. Note the similarity of the wound along the ribs to the channel from the Partition shot into the Test Tube. This initial expansion is exactly why the greatest damage done by most expanding bullets is not far beyond the entrance hole, whether to meat or internal organs.

It’s also why big game bullets expand even on pretty small animals. I once took a reproduction Winchester High Wall in .30-40 Krag on a prairie dog shoot, loaded with 180-grain Nosler Ballistic Tips at 2400 fps. Mostly I wanted to practice with the adjustable tang sight at various ranges before hunting big game that fall, and the very first dog was a typical adult, about two inches thick through the chest. The bullet landed in the chest, where I’d aimed, and while the Ballistic Tip didn’t “explode” the dog, it flopped it right over—and there was an exit hole about an inch wide on the far side, indicating the bullet had fully expanded within two inches.

Big game bullets at higher velocity usually explode prairie dogs, despite being designed to penetrate deeper than thin-jacketed varmint bullets. This isn’t because the big game bullet expanded “too quickly,” as many shooters assume. Instead it worked exactly like most big game bullets work, expanding on impact. Yet hunters who test their big game loads on prairie dogs often assume blown-up dogs mean that particular bullet won’t penetrate on big game, when it will. (If you ever get a chance, try shooting a few Nosler Partitions at small varmints sometime. Most hunters are astounded by the results.)

Occasionally expanding bullets don’t start to open as they hit skin. Some hollow-points don’t, especially if the hollow-point is tiny, or accidentally becomes tiny by being pounded by recoil against the front end of a typical bolt-action magazine. I don’t shoot small varmints with hollow-point centerfire bullets anymore, because plastic-tipped bullets expand much more violently—and occasionally hollow-points failed to expand at all, especially at longer ranges. I’d shoot at a prairie dog and assume the shot had been a miss, because the dog would just stand there—but about the time I started to aim again, the dog would tip over, due to a tiny hole through its body.

Plastic-tipped varmint bullets expand much more reliably, including (for instance) 180-grain Ballistic Tips from a .30-40 Krag. This isn’t because the plastic tip “wedges” deeply into the core of the bullet, another common misconception. High-speed video shows the plastic tip only remains in the bullet’s nose briefly after impact, because as soon as the bullet starts to expand, the increased drag slows it down. The plastic tip then drifts ahead of the expanding bullet, and then off to the side.

Plastic-tipped bullets probably expand more violently because of the big hollow-point where the tip’s inserted, far larger than the tiny hollow-points of .17 to .22 caliber varmint bullets. Plus, the plastic-tip results in a higher ballistic coefficient, so bullets arrive with more retained velocity. A few years ago I was assigned by a magazine to field-test a bunch of different varmint bullets. To compare their performance, I used several rifles that shot bullets of about the same weight to the same point of impact at 100 yards. Plastic-tips not only drifted noticeably less in the wind at any range beyond 150-200 yards, but expanded violently at longer distances as well.

The exception to immediate expansion occurs with some of “hollow-point” target-type bullets used on big game. Most of these have VERY tiny hollow-points, often so small the point of a safety pin can’t be inserted in the hole. As a result, the bullet punches a tiny hole through the skin, and expansion’s delayed until the bullet penetrates far enough for the tip to collapse, rather than expand. You can see this bullet construction in this Berger Match VLD from over a decade ago:


This was the model of Berger that eventually was renamed the Hunting VLD, after many hunters reported they worked very well on big game, partly because of the delayed expansion. As a result, instead of major tissue damage occurring right behind the entrance hole, it started after the bullet penetrated a ways. You can see this in a Test Tube shot with a Berger:


Note how the beginning of the wound channel doesn’t start to widen immediately. Instead it remains bullet diameter, then suddenly opens WAY up at the point where the bullet expands violently. As a result, if you shoot prairie dogs with Bergers, the dogs usually don’t “explode” because the bullet does indeed pass through before starting to expand.

On big game animals, the entrance hole of Bergers is often so small you must part the hair to find the hole, and looks like somebody stabbed the animal with a knitting needle. Yet somehow many shooters insist that Bergers expand violently as soon as they impact—which only proves that they’ve never used Bergers, or any other target-type “hollow-points” that expand the same way.

The most astonishing performance from a VLD for me came late in the season two years ago when taking a doe for a lady in our church. I used a 300 Win mag taking a fat doe (about 180#) quartering on right at 340 yards. At the shot, she did that little 50 yard death run off the power line I was hunting. Recovery was pretty much an easy thing, but I was initially upset that I had gut shot her. She was laying just off the power line and what was inside was now outside. It was a mess.I was a little disgusted that my marksmanship wasn’t any better.

Upon dressing her out I found that I had hit exactly where I had aimed. A pinhole entrance wound was in her left shoulder. The bullet had traversed her body just under her backbone, lodging in the right ham! Apparently the hydrostatic shock while passing through her vitals had split her belly wide open. Crazy.

A similar performance was noted a couple of years prior with a VLD in my M1A. 165, 168 grain...I can’t remember. Again the doe was for another widow in our church that loved venison. About a 75 yard quartering shot laid the doe right there. When I walked up to her the exit wound was rather large and Internal organs appeared to be missing. I looked around and about 15 yards away was her liver...the whole liver. It had, somehow, been pulled or pushed out by the exiting VLD and was laying there in one piece.

Take enough game and you’ll eventually see strange stuff happen I suppose.

Yep, Bergers do considerable internal damage! Once shot a big red stag in New Zealand with a 168 from a .30-06, the range around 250 yards. The stag was bedded down across a canyon, and at the shot it simply tipped back its head, and looked as if it was staring at the sky for a few seconds--then died, without ever trying to get to its feet. The bullet had literally turned the heart into a thin strip of muscle about a foot long, no more than an inch thick anywhere.

For those of us who've used conventional softpoints for a long time, getting used to a bullet that typically makes a MUCH larger exit than entrance hole can take a while. However, I've also found they do so much internal damage that they can placed a little farther behind the shoulder and still kill quickly.

Must also note that I am not saying Bergers (or any bullet) are the absolute best for any given purpose. I test a bunch of different bullets on "media, "varmints and big game, then report what occurs, instead of guessing.

John, have you ever tested cast rifle bullets in the same manner? There are several intuitive truisms associated with their expansion in game, ie: flat nose expands much better than spitzers or even round noses, soft (bhn 10-12) expands better than hard (bhn 16-20), hard bullets tend to shatter their noses, etc. I'll confess to believing them myself and have experiences in the field to back them up, but I'll also admit I may be kidding myself to a degree.

Can you suggest a tutorial on the use of those substances for expansion testing, and perhaps a source of supply?

I haven't done much of the same kind of testing with cast bullets, but just might in the next year, due to buying more and more rifles suitable to their use.

Unfotunately, as I mentioned in the article, Test Tubes are no longer available, basically a casualty of the Great Recession. They were a great resource, because unlike ballistic gelatin, they preserved the bullet channel. Also like ballistic gelatin, they could be melted, poured into a mold, and used again. I can, however, get you some info on where to obtain clear ballistic gel.

Another excellent media for giving bullets a real torture test is dry newspaper. Wet newspaper is used a lot, but unfortunately isn't all that hard on bullets, but dry newspaper provides results very similar to hitting heavy bone. The big problem with newspaper is finding it easily. Twenty years ago Eileen and I subscribed to two dailies and a local weekly, which provided more bullet-test paper than I could use. These days we only subscribe on-line to one of the dailies, and the weekly has become a tiny 8-page flyer. Instead I've started saving grocery store flyers and similar junk mail for testing bullets.

Thanks for the interesting article John.

Have you tried magazines for testing media? I have a bunch I'm getting ready to toss and was thinking I might save a box or two for penetration testing as I've heard newspaper serves well.

Geno

Interesting photos John. My best test media has always been phone books tied together. They change ours out every year or two and a local hotel had all that I needed. The larger mass of a bigger animal can absorb the expansion whereas a smaller animal cannot. An epiphany for me was when I shot a snowshoe hare with a 180 grain Remington round nose ( my preferred deer load at the time) from a .308 and that animal nearly exploded. There was hare parts scattered everywhere. Same thing with a spruce grouse with an '06. Jack O'Connor wrote that the bullet crosses the line of sight twice. True first out at maybe 25 yards, but at 25 feet my grouse head shot wasn't anything but center mass and feathers. All my Nosler Partition deer had lung soup, but smaller diameter exit wounds than I like. I like the idea of the plastic tipped bullets to prevent battering in the magazine, but so far I'm still on the hunt for one that acts more like a soft point that gets deeper penetration. I remember that you wrote once that the newer, tougher SST's might fit that bill. I wish that I could shoot more deer here to test bullets.

Geno,

In general, magazines use slicker, denser paper so are harder on bullets than newspaper.

Windfall,

Actually, with a typical big game cartridge using spitzers, sighted 2-3 inches high at 100 yards, the first "crossing" of the aiming point is a little farther than 25 yards, more like 30-35. Exactly where depends on scope height above the bore, plus the exact load. I am familiar with shooting small game with a big game rifle, since Montana allows hunters to shoot mountain grouse with rifles. Generally I hold on the head to hit the neck.

There are a bunch of plastic-tipped bullets that penetrate deeply, but from the sounds of it you may not want to pay for those that consistently leave a bigger exit hole, like the Barnes TTSX, Hornady Interbond, Nosler AccuBond and Swift Scirrocco II. In bullets that aren't monolithic or bonded, the 165, 168 and 180 Ballistic Tips have very heavy jackets, and tend to act more like AccuBonds, typically retaining 60% or more of their weight (on the rare occasions they're recovered from deer) and like AccuBonds, expanding wider than Partitions.

Part of the problem with new big game bullets is that makers often tweak the design after they're introduced, if the initial construction doesn't please some hunters. Apparently many manufacturers didn't realize how much plastic tips would enhance expansion, and as a result the first Ballistic Tips, SST's and even Sciroccos often expanded more violently than many hunters wanted, which also limited penetration. All three are now tougher (in some models much tougher) than the original bullets.

Of course, impact velocity has an effect as well. A plastic-tipped cup-and-core will tend to hold together better from a .308 Winchester than a .300 Winchester Magnum, ruining less meat and tending to exit more often, especially at closer ranges.

Good read, Thanks MD

Thanks John,

the idea I'm working on, as no bullet companies have shown an interest on their own, for adapting .257 Barnes tsx for 25-20/.256 WinMag use (as required for hunting here in Cali now ) might just work for small game if I can get them to penetrate a foot or so of magazines . They'll be useful should I run across a really tough jackrabbit.

Geno

I did give those Accubonds a try some years back and had the deer go about 90 yards from a broadside middle of the lung shot. What did surprise me on that deer was that the entrance wound was larger than the exit wound. Likely blow back I figured after I shot some water filled gallon milk jugs where I'd added green food coloring. I used my 7mm-08 on those jugs that I sat on a box in the snow. While most of the spray did go out the back side, a lot of it came forward and out to both sides and made a cross pattern in the snow. Lots of guys here sure like that Ballistic Tip for their deer bullet and I'd best try that one, the newer SST or maybe the tried and true Interlock at the range. I swore off Barnes when a TSX buck got away for lack of a blood trail. A quarter size hole through the lungs on one the year before instead of lung pulp should have tipped me off that I needed more expansion.

A great analysis, thanks! I do have an issue with ballistic test media - it may replicate muscle tissue well, but what about lung tissue? A great many hunters prefer lung shots when practical, and the lungs in a living animal are mostly air, which won’t cause bullet expansion. As the bullets do expand fully near the entry point (at least with modern bullet designs) they will pass through lung tissue causing plenty of damage, so perhaps the point is moot.


.

Very interesting stuff, thanks

DoubleRadius,

While there is a lot of air in lungs, there's also plenty of tissue and blood in them too--especially in the area just above and behind the heart and the large blood vessels above it leading into and out of the lungs. Bullets will definitely expand in lungs in the area around the heart.

Where you run into trouble with lungs is at the rear "fringes," far from the area around the heart, where the blood vessels are tiny and the "air pressure" low. Bullets will still expand back there, but won't cause near as much blood or air loss.

There is no single best perfect bullet-test medium, which is why I generally use at least two before actually shooting game with any new bullet--and even then tend to try them first on smaller big game, like doe deer, until getting a better idea of how they perform in a variety of tissue. And even after shooting quite a few animals, surprises can occur, whether due to a bullet not penetrating well through bone, or not expanding much (if at all) when shot broadside through the lungs.

That is an excellent piece MD, very interesting, thank you. For my own part I’m pretty conservative when it comes to bullets, in the sense that I settled on some which seem to do the job quite a while ago, and I’m loath to change. Some have since gone out of production, so eventually I’ll have no choice, though I did lay in stocks of some favourites to carry me for a while.

As a result , while there are bullets with which I’ve killed in some cases hundreds of head of game, they are a somewhat limited selection. There are some more which I’ve given a go, or seen used, and struck off the list after being a bit disappointed – perhaps unfairly given that some might have been used on only a few animals before being rejected.

Most of what I use for deer-sized game are bullets like Winchester Power Point or Remington CorLokt in various calibres. I also have used a lot of Australian made Taipan HP, now largely out of production, and a few others such as PPU, Lapua Mega, Woodleigh, Hornady in a couple of different styles, Nosler ditto (including the old Zipedo, and its various successors), Sierra SP, and factory soft points from S&B, PPU, Geco and others. For deer and pigs though the Winchester Power Point, quite a humble sort of bullet really, does an excellent job for me in various calibres, with Woodleigh RNSP or Lapua Mega my pick for big stuff.

I do share some experiences with yours. For example I’ve shot a fair few rabbits and other small critters (feral cats, hares, foxes) with various deer bullets, from .30-30 velocity to 6 mm. From rifles like the .30-30 or 7x57 (say 2300 to about 2600 fps mv) a typical deer bullet will unzip a rabbit if body-shot. A head shot will neatly decapitate them though, and I have shot a far few t that way for the table. At higher velocities, such as rifles like the 6 mm can reach, a body shot will basically destroy them, and a head shot often causes the whole front half to be unusable. This is with bullets with which I’d happily shoot a deer or pig. On a deer or pig the ideal for me is a bullet which can go through a scapula or bust the spine, but one which will turn the contents of the chest to soup even if it only goes between the ribs to get there. Unlike some I don't much care whether it will go all the way out the far side - the point is a bit moot if the animal is down and dead on the spot.

I have had seen the odd bullet which seemed altogether too fragile. Experience with some plastic-tipped Hornady bullets a good while back put me off them, for example. I’ve also seen some which seemed a bit slow to open up on smaller game too – Woodleigh’s PP in 9.3 for example, performed beautifully on buffalo for me, consistently fetching up as a lump under the skin on the far side, and looking exactly like the advertising photographs, but did not seem to kill well on smaller pigs (maybe 80 – 100 lbs) or wild dogs. I suspect in both cases, Hornady and Woodleigh, the bullets were perhaps being used outside their design envelope, and in the case of the Woodleigh the RNSP version in the same weight has performed markedly better on the smaller stuff as well as a dozen or so buffalo. Perhaps my 9.3 wasn’t driving the PP version quite hard enough to perform well on the smaller animals.

Dan,

Thanks for your experiences.

I noted in another post a couple years ago that Hornady has apparently toughened up the plastic-tipped SST, which you (and many others) found fragile when introduced. I was put off by them myself, but in late 2017 went on a deer/pig hunt in Texas, where several writers and various industry representatives all used the mew Franchi bolt-action rifle in .308 Winchester, with Fiocchi factory ammo loaded with the 150 Scirocco. Obviously the velocity isn't super-high (I believe it's listed at 2820 fps) but we NEVER recovered a bullet on deer and pigs weighing up to 200 pounds, at ranges that were almost all within 150 yards. This was even with a double-shoulder shot on a big boar, and severe angling shots on some sizable deer.

Have seen some of the really good BIG game bullets not do much internal damage on smaller animals, when started at modest velocities. Hornady loads a 250-grain GMX (their monolithic bullet, which acts very similarly to the Barnes TSX) in the 9.3x62 for sale in Europe. On another Texas hunt, one guy used it on a big nilgai bull (around 800 pounds) where it worked great, but he also shot a 50-pound eating pig perfectly just behind the shoulders, and it went around 75 yards with no sign of a hit--though it was thoroughly dead when we found it.

A couple of points with regards to ballistic medium testing for people that do not know-

The ONLY medium that has been proven and correlated with live tissue results is properly calibrated 10% ballistic geletin. Clear ballistics gel, test tubes, etc are neat, and can show comparisons between bullets, however no correlation between what a bullet does in them and what it does in live animals should be assumed. I.E.- 12” of penetration in a test tube/clear ballistics gel, water/etc does not equal 12” in animals.

Newspaper, phone books, etc. often give the people doing the shooting a false idea of what the bullet will do IME.








The organs, including the lungs are mostly water. Bullets expand very similarly in organs as they do muscle. Large bones are harder of course, but often not as much a problem as some think.

I use a lot of Hornady BTHP Match bullets on pigs and goats, especially in .224 / 75g and .243 / 105g. I’ve also shot quite a few of them into wet and dry newspapers and magazines.

They exhibit the same quality you set out above. Several inches of almost no expansion, then very significant expansion and wounding. They also penetrate usually quite a bit deeper than soft points or plastic points.

I recommend them.

bobnob,

Thanks for the follow-up.

As noted in the article, that has been my experience with other HP match bullets than Bergers as well, though the Bergers tend to expand somewhat more violently than some, once they do start. I suspect this is because they have pretty soft cores, or the original Hunting VLD's did. Walt told me when they rebranded the original "Match Grade" VLD;s in 2007 as the Hunting VLD that the cores were as close to pure lead as they could get, about one-half of 1% antimony. In contrast, some other match hollowpoints have 3% or so antimony, so don't expand quite as violently.

What have in common, however, is a long "hollow-point" nose that's hollow BEHIND the tip. The reason I put "hollow-point" in quotation marks is in general it isn't a hollow-point, incapable admitting even the tip of a typical safety pin. But the air-space behind the tip allows the frontal jacket to collapse, expanding the bullet after several inches.

Another interesting thing about testing various bullets in different kinds of media is that supposedly actual hollow-points (those with a hole that accepts a safety pin's tip) require liquid entering the HP to expand. But I have yet to shoot such a bullet into dry newspaper and have it fail to expand.