Bullet design

by Ian Thompson

There is a bewildering array of hunting bullets on the market today and these bear a bewildering array of fancy titles - probably bestowed on them, in a blinding midnight revelation, by some public relations genius in the company concerned. These names are generally designed to be spectacular rather than informative, but this, unfortunately, may not be much help to the shooter when he is trying to make an informed decision.

For instance, is it better to have a round nose than a spitzer nose (all referring to the bullet of course, not the hunter)? And does a pointy head (on either the bullet or the shooter) help or hinder? We can probably all agree than a runny nose is a darn nuisance (referring to the shooter, not the bullet), but what else can we agree on?

Perhaps not much, unless we can get a bit more information on which to base our agreement (or lack of agreement).

Here I will try to explain why certain bullets are constructed in certain manners and whether or not the design will assist you in your own search for the ‘perfect bullet’.

The first general bullet design we’ll consider is that of the full metal jacket (FMJ) type. Throughout the years the media have done a pretty efficient job of smearing the name of the FMJ until, to them at least, it personifies all that is ‘evil’ in the ballistic world. The truth, however, is a bit less spectacular in that the name merely covers those bullets in which the outer copper jacket is drawn completely over the lead core at the nose so that no lead is exposed there. The base of such a bullet may or may not be similarly covered - as far as this article is concerned, it makes no difference.

The main feature of such bullets is that the nose is particularly rigid and will not deform, other than on very hard targets such as metal plates, etc. The FMJ is thus capable of extremely deep penetration in softer materials and is therefore not much use for hunting, other than perhaps on the odd dinosaur that may still be lurking around, so we won’t spend much time on it. It is, however, widely used in military circles for reasons that are largely concerned with the Hague Convention and the need for military bullets to feed through machine guns. I’ll leave you to decide which is the more important to them.

The next most important type is that where the copper jacket does not completely cover the tip of the bullet, leaving a portion of the lead core exposed at the nose, which gives them their generic name of ‘soft-points’ (SP). Most hunting bullets are of this nature or perhaps some variation of it. This exposure of the softer lead core has a number of ramifications, some good and some bad.

Let’s get rid of the bad bits first. A bare lead tip of this type is of course more easily damaged than a solid copper tip. Undue rough handling can thus easily bend, flatten, shave or otherwise distort this tip, which does nothing for the accuracy. A bit more care will generally avoid this type of trouble, but it pays to remain aware of the problem. Rough handling when reloading such bullets can also cause a build-up of lead shavings inside the dies; again, a bit of care will avoid that embarrassment.

Now for the good news. This bare lead tip will also distort fairly readily when it hits a target and the beauty of this system is that if the nature of the target and the impact velocity of the bullet are both known, the shape and length of this tip can be tailored to give a certain desirable amount of distortion and as a result a certain desirable degree of penetration.

Following impact with most kinds of targets of hunting interest, this distortion takes the form of the lead tip folding outwards and backwards upon itself until it gets some support from the copper jacket. The distortion then stops, leaving the bullet looking somewhat like a mushroom with a rounded oversized head of lead and a stem of copper. In fact, the name ‘mushroom’ has been given to this type of distortion/expansion and is a widely recognised term.

It is this ‘mushroom’ head that massively increases the drag of the bullet through the body of the target and which finally brings that bullet to rest - hopefully while still inside the target. If the extent of this mushrooming is large, the bullet will stop all the sooner (ie, it will give a shallow penetration). Conversely, if the mushroom head is small, the bullet will penetrate more deeply.

We have thus derived our first practical design for a hunting bullet - it will have a sharp point that will allow it to penetrate the air easily and to arrive at the target with a fair bit of its original velocity still remaining. This point will be formed from the bullet’s lead core and the body of the bullet will be supported along most of its length by the copper jacket. On impact this lead tip will mushroom out to a known degree, but the bullet will not simply disintegrate since the jacket is still holding it together. So far, so good.

But, as discussed earlier, all targets are not the same. This means that, to a greater or lesser extent, the expansion of the bullet has to be tailored to the target, which in turn means that separate bullet designs are needed for each type of target. A long, bare, lead tip with a short thin jacket would give a bullet that mushrooms easily on a light target like a fox, while a shorter, blunter nose supported by a thicker jacket would hold together better for deeper penetration into a pig. This, on paper, is a very neat and tidy solution to the problem, but quite unworkable in the field, since you may well run across a pig when you are loaded with ‘fox’ bullets and vice versa.

This very real problem can be solved (more or less) by recourse to the gentle art of compromise. The new bullet can be made, say, just a bit more solid than would be best for foxes, but not quite as solid as would be desirable for pigs. Then, whether you run across a fox or a porker, you’ve still got some capability of a decent kill.

And that last phrase is a key one. Some shooters are opposed to compromise in any shape or form, thus there will always be a market for soft-nosed bullets with thin jackets (for light game), with thick jackets (for heavier game) and for all sorts of in-between compromise designs for use where the type of game cannot be readily predicted or where the shooter simply wants to standardise on just one bullet.

A lot of ingenuity has gone into the design of some of these ‘compromise’ types, often with a fair measure of success. In general, the jacket of such types have been modified in some way so that the expansion is fairly easy in the early stages of penetration, but becomes progressively harder as the bullet penetrates more deeply. These are often known as ‘controlled expansion’ types and some of them are very cunning indeed. Probably the simplest such design is where the jacket is relatively thin at the nose but quite thick near the base; this controls the expansion quite well, but introduces a few new problems in the process. Due to the increased amount of copper, such bullets are lighter for a given length and this can cause problems with fixing a suitable twist rate for the barrel. Furthermore, the very thick base can stop the bullets from expanding/engraving properly in the bore and that can lead to accuracy problems that are hard to track down and most unwelcome.

Another solution is that of making the jacket fairly thin overall, but of also providing it with longitudinal internal reinforcing ribs that control the way that it can peel back. In a variation of this same theme, the jacket can be made fairly thick overall, but provided with weakening slits down the inside. This general idea works well and gives fewer accuracy problems than other types, but such bullets are more expensive to make accurately - and you don’t want inaccurate ones do you?

A final example is that where the jacket is formed with an internal partition right across it about halfway down the body. The front part can then be made fairly soft to give good early expansion while the back half remains fairly solid to ensure deep penetration with at least half of the original bullet. A good compromise performance is assured, but they can be a bit expensive for general use.

The third general type is that generally known as the ‘hollow point’ (HP) and that name describes them nicely. The main feature of such designs is that of a hole in the nose (of greater or lesser diameter) extending partway back into the body of the bullet. This hole obviously assists the bullet nose in expanding and is of great help in that regard where the bullet will have only a moderate velocity (eg, as from a pistol, one of the older cartridge types such as the .44/40, or the .22RF, etc). One other advantage of the HP design is that the jacket can be made quite heavy, if need be, without greatly affecting that bullet’s ability to expand adequately.

These HP bullets have also been savaged by some of the more rabid parts of the media, but they have a perfectly legitimate niche in the bullet-design family. They are often known as ‘dum-dum’ types, whereas that name more accurately refers to their soft-nosed brethren.

Variations on the simple HP design include those where a small, tapered, metal or plastic plug is inserted in the hole to improve the air flow and to assist expansion on impact, but to resist accidental damage to that relatively fragile area during loading and handling. Again, these can be very good bullets, but a bit more expensive.

It’s obviously impossible to cover all bullet types in one article like this, but at least you can now get to know the main variations along with their major pros and cons. You can then start to weed out those that don’t look at all promising for your style of shooting. After that, it’s up to you to try out a couple of the more promising designs and to talk things over with a few of your more experienced mates at the club - they’ll possibly even let you have a couple of their favourite ones to try for yourself.

Remember that there are few, if any bullets, that are no good at all, but there can be quite a lot that, for one reason or another, just don’t suit you. The other thing to remember is that the cost of the bullet itself is usually only a very small proportion of the overall cost of a hunting trip. However, the success (or otherwise) of the whole hunting trip can depend on that one little item - so it’s well worth taking a fair bit of trouble to get it right.

Captions
Image 1: Showing a Round Nose Soft Point bullet (RNSP) before and after impact. The degree of ‘mushrooming’ has been controlled by the thickness of the jacket.
Image 2: Showing a typical construction of Hollow Point (HP) bullets for a rifle at about 2000fps Impact Velocity (left) and a pistol at about 800fps Impact Velocity (right).
Image 3: Based on an old German design called the ‘H Mantle’, this type of partition bullet is probably the ultimate in controlled expansion.