Rifle Bullet Designs
April 18, 2019
As it happens each late summer and fall, hunters head into the field. Before they go, the annual argument ensues about which bullet is best for hunting. Since most (if not all) of the hunting seasons are over, I felt it would be worthwhile to discuss the characteristics of different bullet types to better prepare you for next hunting season.
Bullet makers have done a masterful job coming up with catchy names or acronyms for their new bullets. There’s Federal Edge TLR, Hornady ELD-X, Remington HTP Copper, SIG Sauer HT and Winchester Deer Season XP, to name a few. If you search online for bullets, the list of names can make you dizzy.
With that said, there are really only several types of bullet designs. What follows is a top-level view of rifle bullet designs and considerations for choosing the best projectile for your needs, and what the pros and cons are of each. I’ll also touch on some design characteristics to consider for different applications.
Rifle bullets can be separated into two general types: jacketed or solid. Jacketed bullets are constructed of a metal jacket (aka sleeve) and a core. The most common metals used for jackets are gilding metal (i.e., copper alloy) or copper-plated soft steel. A lead core is most often pressed into the jacket. Some military bullets feature a soft steel core. A subset of jacketed bullets is the bonded bullet. These have the lead core bonded to the jacket.
Full Metal Jackets
There are a number of different jacketed bullet types. There’s full metal jacket (FMJ), hollowpoint (HP), soft point (SP) and partition. Within most of these types, there are features that improve performance such as polymer (aka ballistic) tips and boattails. Many manufacturers have trademarked features meant to provide a performance improvement. An example of this would be the Hornady InterLock.
FMJ bullets are made with a jacket and have a lead or soft-steel core. The nose of the bullet is a solid jacket material with no exposed lead. Usually the rear of the projectile is open. Designs can be found that are totally copper plated with no exposed lead. The Speer TMJ bullet is such an example.
The FMJ bullet design was one of the first jacketed-bullet designs, developed in the late 1800s as a nonexpanding bullet to satisfy military treaties. Commonly found commercial FMJ bullets are usually .22 or .30 caliber and mimic a military bullet design.
Commercial FMJ bullets are usually accurate, but not quite to the level of offering a better hunting or match bullet. Military manufactured FMJ bullets usually leave a lot to be desired in terms of accuracy. Sporting applications for FMJ bullets are when expansion is not desired such as for pelt hunting or small-game hunting as well as plinking.
FMJ bullets can also include heavy-duty bullets designed for dangerous-game hunting. Bullets in this category often have heavy copper or copper-clad steel jackets with hard-lead cores. These bullets are designed to avoid deformation on impact, to retain all their weight and penetrate very deep. Generally, these bullets have large, blunt noses that minimize deflection when hitting bone.
The nose of HP bullets contain no core material. This type of bullet typically has a fairly thin jacket. The hollowpoint does several things for the bullet. The hollow cavity in the nose moves the center of gravity of the bullet to the rear, which provides some accuracy advantages at short to medium ranges. No core material in the nose allows the point or meplat of the bullet to be formed up smaller. This allows improvement in the aerodynamics of the bullet over the SP type.
If the tip is not brought to an extremely sharp point and left slightly open, it can provide rapid expansion as well as expansion at low velocities. HP bullets with very small points don’t expand and either completely penetrate like an FMJ or tumble at some point along the path through the target. These sharply pointed HP bullets provide very unpredictable terminal performance.
Lastly, because of the metal nose, HP bullets are not affected by flattening of the nose during recoil while in the magazine, unlike SPs and some polymer-tip bullets. This prevents changes in downrange trajectory and terminal performance. Applications for HP designs include target shooting and varmint hunting.
Soft Points Soft points are the oldest design of expanding jacketed bullet and have been around since the late 1800s. They are made by forming a metal jacket and pressing a lead core into the jacket. The nose is formed, and a small amount of lead core is squeezed out the top of the jacket and shaped to a rounded point.
When the SP bullet strikes a target, the exposed lead begins to crush and mushroom, which forces open the jacket and causes the bullet to expand. SPs don’t have the flashy appeal of the bonded, tipped bullets, but they are still around because they are effective.
SP bullets can be very accurate, have effective terminal performance within moderate ranges and are usually the lowest-cost hunting bullet. However, they can have jacket-core separation from time to time, which can reduce terminal performance.
In my experience, SP bullets will expand reliably down to about 2,000 feet per second (fps) of remaining velocity. Much below this and they will act like an FMJ. If you are the casual hunter and typically hunt at moderate ranges, say out to 250 to 300 yards, an SP bullet will do most anything you want it to and cost less.
Partition-type jacketed bullets were developed by John Nosler, Sr., in the late 1940s. This design starts as a cylindrical billet of copper and is formed from both ends, so the jacket has a solid bulkhead in the middle of the bullet. A lead core is pressed into both ends of the jacket and the nose is formed like a conventional soft-point design.
This bullet set the standard for some time for its tough, deep-penetrating design with improved weight retention over traditional SP bullets. Improvements to the basic design have been made over the years by bonding and adding a tip, but partition bullets still offer very good terminal performance. They can be a little difficult to get the best accuracy out of, and they can be a little more expensive because they are more difficult to make.
Bonding is usually a heat process where the lead core is bonded to the jacket. The jacket and core cannot separate, but react and expand as one. This results in tough bullets that have high weight retention, typically better than 90 percent. They also frequently produce very deep penetration, but not to the extent that solids do.
Because the bonding process often uses heat, bonded bullets will usually have thick jackets. The heat used in the bonding process anneals the jacket back to a relatively soft condition, and the jacket has to be made thicker to achieve the required strength.
Bonded bullets usually have soft, pure lead cores because alloy leads will not bond. Bonded bullets are an obvious choice when hunting large, tough animals where deep penetration may be needed and extremely reliable terminal performance is a necessity. Bonded bullets tend to be not as accurate as nonbonded bullets because of the thicker jacket and the associated difficulty of getting a concentric jacket. However, I have never seen one that did not produce the accuracy you’ll need for hunting. Bonded bullets are usually some of the most expensive bullets because of the complicated process to manufacture them.
Solid bullets are usually a solid piece of a copper alloy. They can be made by turning them on a lathe or by a forming process on a traditional bullet press. Solids can range from one that’s completely solid to another that has a cavity formed in the nose similar to a hollowpoint. Such a cavity may be used to house a polymer tip in the nose.
These latter solids, developed in 2003 by Randy Brooks of Barnes Bullets, are designed to be controlled-expansion projectiles for hunting. Solids meant for hunting include the Barnes triple-shock expanding (TSX) bullet and the tipped, triple-shock expanding (TTSX) bullet, Federal Premium’s Trophy Copper, Hornady’s gilded metal expanding (GMX) bullet, Nosler’s expanding-tip (E-Tip) and Winchester extreme point (XP) copper. These have all earned reputations as efficient hunting bullets with nearly 100 percent retained weight and effective penetration.
When people complain that solids are too light, I like to remind them that they lose no weight when penetrating. A given-weight solid will perform like a much heavier lead-core bullet. A 30-caliber, 150-grain solid will perform terminally like a 190-grain, lead-core bullet that’s going to lose 30 to 35 percent of its weight while penetrating. Solids are typically a little pricey because they are all copper and copper is more expensive than lead.
Solids can be a little difficult to get to shoot as accurately as some might expect. I have never encountered any solid that was not what I consider to be hunting accurate.
A word of caution when hunting with solids; make sure another animal is not standing behind the one you are shooting at. Most of these bullets have a lot of penetration and could very likely hit both animals. In my experience, most of the solids will expand reliably out to 400 to 500 yards. The tipped ones will give about 100 yards of additional, effective expansion.
Tips & Tails
Let’s discuss tipped bullets and boattails. Tipped bullets were developed by Nosler and introduced in 1989. They were, and still are, a very good idea.
The tip does a number of things to enhance bullet performance. First, they give a smaller point diameter on the nose, which benefits aerodynamic performance and improves retained velocity and trajectory. As a result of being a molded-polymer tip, the shape of the nose is extremely uniform from bullet to bullet and lot to lot. This improves consistency of performance.
Last but not least, a properly constructed tipped bullet will have a gap under the shank of the tip that allows the tip to set back into the jacket when it impacts. This ensures rapid and reliable expansion. The combination of having higher retained velocity than a soft point and a better mechanism for initiating expansion results in expansion at lower velocities and greater range.
Typical tipped bullets will expand reliably down to velocities of about 1,800 fps. New bullet designs such as the Federal Edge TLR and Hornady ELD-X have extended this expansion velocity down to the 1,500- to 1,600-fps range. These two bullets, with their very high aerodynamic performance and terminal performance at very low velocities, will excel at extreme ranges.
Boattails have been rather misrepresented over the years. A boattail is a bullet feature that lowers the drag of the bullet, but it only does this effectively below a certain velocity range. Predominantly, a boattail does not have a lot of effect until the bullet has slowed down below 2,000 fps. The boattail also has to be at least half a bullet diameter long and have an angle of 8 degrees or less to have much effect. Many of the bullets you see with a very short or steep angled boattail have virtually no aerodynamic advantage over a flat base.
Boattails can be difficult to get to shoot well out of some guns. I have largely found that a rifle that doesn’t favor a boattail bullet will usually produce better accuracy with a flat-base bullet. If you are the 250- to 300-yard hunter, a boattail bullet gains you very little. The table illustrates the trajectory of bullets that are identical except one has a flat base and the other has a boattail. I sure can’t differentiate .2 or .8 inch in trajectory at 300 and 400 yards with a field rest. So, the differences in retained velocity mean nothing. However, for long-range shooting, say beyond 500 yards, a boattail has an increasingly significant effect on trajectory and retained velocity.
So, there’s the differences between bullet designs on the market to help you make an informed decision on what bullet type would best meet your needs and help you avoid spending money on features you really don’t need.