Why Handgun and Rifle Bullets are Different.
Many people have noticed that rifle and handgun bullets are quite different and wondered why. Handgun bullets tend to be short and fat, while rifle bullets are (relatively) long and thin. For example, #M855A1 is the current 5.56mm U.S. military rifle round and it uses a 62 grain weight, .224” diameter bullet. The standard U.S. #M882 9x19mm handgun cartridge uses a 112 grain, .355” diameter bullet. The handgun bullet is 1.8 times heavier and the diameter is 1.6 times greater than the rifle bullet.
The difference in barrel length and operating pressure between hand guns and rifles is what largely causes this difference. Some readers are probably nodding in agreement and everyone else is still confused, so permit me to elaborate.
The gas pressure generated by combusting gun powder pushes the bullet out of the barrel of any firearm. The gas pressure pushing on the base of the bullet base is continuously accelerating the bullet. A bullet's muzzle velocity is largely a matter of gas pressure and having a sufficiently long barrel to allow full acceleration. Therefore, relatively short barreled handguns are at a great disadvantage compared to rifles and thus limited to much lower muzzle velocities. Bullet velocity is the most important component is calculating bullet energy and it is energy that powers bullet expansion and penetration.
Typical handgun muzzle velocities generally run from about 750 FPS (feet per second) to 1,300 FPS. This is true for all calibers, from .22 through .45. On the other hand, rifle velocities generally run from 1,900 FPS to 4,000 FPS. Handgun bullet designers are faced with the basic limitation of a short barrel that produces lower velocity and yet they desire to maximize effectiveness. To improve a bullet's terminal performance, you can do six things:
1. To increase handgun bullet effectiveness in the same caliber you might increase the bullet weight by making it longer. However, the muzzle velocity starts to drop. There is no magic bottom limit but I think most people would agree that 750 FPS is near the bottom limit for effectiveness. I have seen 1200 FPS suggested as a good handgun bullet velocity. To maintain higher velocity, the weight of the bullet must be limited. This makes it easier for the combustion gas pressure to accelerate the lighter bullet. You generally end up with a stubby bullet where the length is only 1.4 to 2 times the diameter. Handgunners would like to use a longer heavier bullet, but it just comes out too slow.
2. You can increase the barrel length to allow a longer acceleration time. This is limited by the desire for a handgun to be small and easy to carry. If you could carry a rifle, you would. Thus, 8" is about the maximum practical barrel length for handguns intended to be carried in a holster and 4-6" is much more common.
3. Another possibility is to increase the operating pressure of the cartridge. This has been done and modern cartridges operate near the limit allowed by current metallurgy in a handgun intended for holster carry. The different handgun and rifle cartridges have different allowable maximum pressures, depending upon the state of cartridge design during the years they were developed or pressure limits due to the firearm that was intended to use the cartridge. Handguns generally operate at lower pressures.
4. Increase bullet diameter (caliber) to make a bigger hole in the target. For self defense and hunting applications, calibers in the .35" to .45" range are most popular. Increasing the bullet diameter allows the pressure generated by combusting gun powder to push on an increased bullet base surface area. If the same pressure (Pounds per Square Inch) is pushing on a larger rear bullet area then you can increase the bullet weight and still get about the same velocity.
For example, compare the bullets from a .22 WMR cartridge (.224”) and .45 APC +P cartridge (.452”). Both have similar operating pressures of about 24,000 PSI. The base of the .45 has 4.1 times the area of a .22 bullet. Therefore, we should be able to use a bullet that much heavier and get a similar velocity. A typical bullet for a .22 WMR is 40 grains and is driven at about 1300 FPS from a 4” barrel. A comparable bullet for the 45 APC +P cartridge should be 164 grains. In fact, a couple ammo companies offer a 165 grain load for this cartridge that obtains about the same velocity as the .22 WMR. The point is that you can throw more lead with a larger caliber (diameter) to improve effectiveness. The limit on this is recoil and gun weight. As the bullet gets heavier, the recoil gets heavier and the gun gets heavier. Observing firearm history, it seems that .45 is about the maximum practical handgun bullet diameter.
5. You can improve the bullet design to achieve greater terminal effectiveness. There has been a lot of bullet development and improvement in the last 40 years. Better bullets have improved performance for all handgun and rifle calibers. Improved bullets have made some smaller calibers a more versatile and deadly. For example, the .45 was popular for most of the last century. However, now bullet diameters from .355” to .40” seem more popular. Part of the reason that the .45 size was popular was that bullets did not expand reliably on impact, so starting out with a larger diameter bullet helped insure a bigger hole in the target.
6. Finally, you can improve the propellant (gun powder) to get a more sustained push with lower peak pressure. This has been an ongoing process since the development of modern smokeless powder over 100 years ago. Recent improvements in gun powder have had some effect, particularly for use in short barreled handguns, but they have not caused any essential change in the short fat nature of handgun bullets.
During the black powder era, rifles were limited by the nature of black powder. Black powder could only generate limited pressure and the only practical to increase terminal effectiveness was by increasing bullet diameter. My old Lyman Black Powder Handbook, 1st edition, lists 16,000 CUP (not directly convertible to PSI) as the highest pressure generated by any of the black powder loads. Some modern rifle cartridges operate at 60,000 PSI, or about 3.75 times as much.
This is why so many typical black powder cartridge rifles were .38, .40 and .45 caliber. Some muzzle loaders were even larger, such as the .75 caliber Brown Bess. With the development of modern smokeless gun powders, we can generate higher pressures with resulting higher velocity. Rifle bullets then started to become long and thin for a number of reasons:
1. A rifle shooting a big, heavy bullet at high velocity will kick like the devil. (Try a .458 Magnum and see for yourself!) At higher velocities, smaller diameter bullets will do the job and not hurt the shooter as much.
2. Long bullets are more streamlined and achieve a higher ballistic coefficient than short, fat bullets. This increases their effective range.
3. Long bullets also penetrate the target better. This is due to increased sectional density. Ensuring adequate penetration coupled with reliable expansion to maximize terminal effect is an ongoing concern with handgun bullets, largely due to their relatively low impact velocities. However, it is relatively easy to combine adequate penetration and good expansion at the higher impact velocities associated with modern rifle cartridges.
4. Rifles have velocity limits, but, we can generally select as long and heavy a bullet as we need in a particular caliber and drive it fast enough for adequate and reliable terminal performance. Since rifle cartridges sometimes have velocity to spare, people will occasionally get a shortened (carbine length) barrel to decrease rifle weight and improve handling. They are willing to sacrifice some velocity. My favorite .308 Winchester load uses a 165 grain bullet. This bullet is 3.6 times longer than its diameter and yet this is a medium weight bullet for the caliber. That ratio is much higher than the typical handgun bullet ratio of 1.4 to 2.
Thus, rifle bullets tend to be proportionally thinner and longer than handgun bullets. Due to longer barrels had generally higher operating pressures, rifle cartridge bullet velocities are generally higher and consequently less of a limiting factor in terms of achieving satisfactory terminal performance.
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