Posts Tagged ‘Ballistics’

Colt Delta Elite - One attempt to harness the 10mm

Cartridge of the Week, the 10mm, 10mm Auto

Those who have followed my posts know I have one foot in the past and one barely in the present when it comes to firearms and cartridges. It takes a lot of evidence and time to prove something to me. Nothing like the tried, true and tested. Nevertheless, I cannot argue with the point that somethings are good right out of the box, like the Colt Python, wait there I go again. Another thing that is hard to argue with is physics. Well you can, but people will see you talking to yourself and runaway. When it comes to physics and raw proof, there are few cartridges that rival the mighty 10mm Auto.

Bullet Impacting Brass Rod

Terminal Ballistics

This is the third part of our study on ballistics. First, we looked at interior ballistics which is what happens when the shooter fires and the bullet is still in the gun. After that, we briefly examined exterior ballistics, which is what happens once the bullet leaves the muzzle of the gun and the forces that act on it as it travels to the target. Now we will look at terminal ballistics. This is what happens once the bullet arrives at the intended destination.

Exterior Ballistics

Exterior Ballistics

I am often amused as I read some of the trifling on the Internet of the person who wants to buy their first rifle for the purpose of shooting 1,000 yards. This arbitrary distance seems to have become the standard for being an expert shooter. The homemade sniper for some sort of future zombie attacks.

30-30 Winchester

Cartridge of the Week 30-30 Winchester

Last week we explored an old Warhorse, the Russian 7.62x54R. This week we look into a staple cartridge of hunters for many years, the 30-30 Winchester. Just slightly older than last week’s cartridge by just four years (1895) it is still in use today and may have harvested more deer than any other smokeless cartridge. Also known as the 30-30 WCF, a name derived from a .30 caliber bullet loaded with 30 grains of powder. Designed in a time when there were numerous amounts of rimfire and centerfire cartridges, the need existed to define it as centerfire cartridge.

Bullet Exiting Barell

Interior Ballistics

There are four types of ballistics, interior, exterior, terminal, and forensic. Today we will tackle interior ballistics. Watch my posts over the next few weeks to explore the other ballistic theories. These are very basic principles. Each one is an extensive and fascinating study in physics and math. Please do not let the math and physics scare you. I hope that you will continue to explore these fascinating theories.

Did You Know…

The world record for the smallest 100-yard benchrest group was shot in 1973 by Pat McMillan using a handbuilt prototype McMillan rifle with an early McMillan stock. The 5-shot group measures a mere 0.009-inch center to center and was examined with a 60x microscope for verification. The record still stands today, and the actual record group, plus the McMillan rifle that shot it, hang in the company’s museum in Phoenix.

Rounds to Incapacitation

Trainer: For Self-Defense, Carry What You Want

Greg Ellifritz, a full-time firearms and defensive tactics training officer for a central Ohio police department and the president of Active Response Training, recently conducted an extensive self-study of cartridge and shotshell stops. He graciously allowed the CTD Chronicles to excerpt some of his findings—which challenge conventional wisdom about which cartridges are best for self defense.

32-20 Winchester

Cartridges that Make You Ask Why

Not every caliber does a particularly good job at filling its role. We can’t all be a .308 I suppose. I will say however, that any caliber is better than none. If I had to choose between carrying an anemic cartridge or no gun at all, I’ll take the anemic cartridge every time. That being said, some calibers make you step back and wonder why they ever made them at all. We looked through some gun history and came up with some pretty odd performing bullets.

Will the Best Medium Sized Cartridge Please Stand Up

It can be a difficult decision when trying to decide what deer-hunting cartridge to go with. So often, we are stuck on how well these rounds do at four and five hundred yards, we forget that most of time, we take shots inside of one hundred yards. We decided to take a look at some cartridges designed for medium-sized game, like Texas white tail deer. So how well do these common rifle cartridges do against each other? We took a look at some common rounds, and tried to help our readers decide for themselves.

.30-30 Winchester

.30-30 Winchester

.30-30 Winchester

The first cartridge in our list was actually the first .30 caliber round that propels itself with smokeless powder. The .30-30 cartridge has probably brought down more deer than any other rifle cartridge. Put into production in 1895 for the Winchester lever-action rifle, the .30-30 soon gained popularity as the smokeless powder it used allowed for faster follow-up shots and significantly reduced fouling in the barrel and action. This soft shooting round has an effective range of only 200 meters but with a 170-grain flat point bullet, it hits hard enough to drop all but the largest CXP2 Class animal.

.243 Winchester

.243 Winchester Cartridge

.243 Winchester Cartridge

The .243 Winchester is a popular round for youths and new shooters who dislike the harsh recoil of larger calibers. Though it is soft shooting, the .243 is more than capable of taking down any medium-sized game animal, from feral hogs to large white-tailed deer. BVAC’s 100 grain Grand Slam is an easy to shoot round with a maximum point-blank range out past 300 yards, depending on the size of the game animal. Hornady’s Varmint Express topped off with a 58 grain V-Maxon the other hand is an extremely fast and flat shooting cartridge that travels over 3750 feet per second at the muzzle, making it an excellent varmint round out to 200 yards. Their Superformance ammunition is even hotter, throwing a 58-grain projectile down range at over 3925 feet per second.

.270 Winchester

.270 Winchester Cartridge

.270 Winchester Cartridge

With the release of the Model 54 bolt-action rifle, Winchester unveiled the .270 cartridge in 1925. Writer Jack O’Connor who wrote at length about it in Outdoor Life and other publications praised it highly, but the round never enjoyed great success for nearly 20 years. After World War II, it saw an enormous surge in popularity, becoming one of the most widely chambered calibers for hunting rifles across the globe. Loaded with a 100 Grain cartridge, Remington Core Lokt PSP achieves a muzzle velocity in excess of 3,300 feet per second. This extreme velocity makes the .270 a very flat shooting round with devastating terminal ballistics. Loaded up in a heavier 150 Grain Federal with Sierra Game King the round is effective on larger game animals like moose or elk. The middleweight 130 Grain BVAC Grand Slam is a good all-around cartridge for hunting a variety of medium sized game.

.25-06 Remington

.25-06 Remington

.25-06 Remington

For decades, the .25-06 was just a custom round created from a necked down .30-06. When Remington began producing the round as a factory load in 1969 however, it experienced a surge in popularity. Topped off with a 120 Grain Speer Grand Slam bullet the BVAC .25-06 cartridge generates a muzzle velocity of 2898 feet per second, and when topped with an 85 Grain Nosler Ballistic Tip Federal’s V-Shok load reaches a velocity of over 3550 feet per second. This zippy little round may be a small caliber, but its flat trajectory and deadly terminal ballistics help it to remain popular among varmint and medium game hunters. Despite the small size of the .25-06, it has superior sectional density at higher bullet weights. The 115 Grain Winchester Ballistic Silvertip has a ballistic coefficient of 0.446, giving it penetration and performance comparable to larger .30 caliber rounds.

So, these rounds all work well for medium-sized game, they shoot flat and have tons of energy. They are all perfectly capable of dropping a white tail deer in their hooves. Which cartridge works best? Comment below and let us know what kind of luck you have had with these rounds. Personally, I’ve always had luck with my .270, it’s not overkill for white tail, but I can still bring down an elk if I choose. Just wish we had some elk down here in Texas.

Ballistic Coefficient

For many shooters, figuring out the ballistics of their rounds is akin to some arcane form of black magic. There are so many variables involved, and some of these variables have a much greater effect than others. Everyone is basically familiar with the effects of bullet weight and muzzle velocity, and a basic computation of your external ballistics and bullet trajectory can be computed using simple physics formulas that disregard atmospheric conditions and aerodynamic drag using only these components. But there is one aspect of aerodynamic drag that does have a significant measurable effect on bullet trajectory, and that is the ballistic coefficiency of the bullet. But what is a ballistic coefficient?

Hornaday A-Max .308 caliber 208 grain bullet. Note the spire pointed ballistic tip and aerodynamic boat tail, giving this bullet a high ballistic coefficient.

In the simplest of terms, the ballistic coefficient (or BC) of a bullet is the measure of its ability to fly efficiently through the air. Spire points or spitzer rounds obviously pierce through the air better than round nose bullets, and a bullet with a flat base generates much more drag than a bullet with a boat tail design. The number that designates the BC of a round is generally represented as a decimal measured in lb/in², with a higher number indicating a more streamlined bullet with a higher sectional density.

The sectional density of a bullet plays heavily into the resulting ballistic coefficient. The sectional density is the ratio of the diameter of the round and its weight. Computing the sectional density of a bullet is fairly straight forward: simply take the mass of the bullet and divide it by the diameter (caliber) squared. A heavier bullet will have a better (higher) sectional density than a lighter bullet of the same caliber. For this reason, bullets that are lighter tend to have a lower ballistic coefficient than heavier bullets (assuming of course that the bullets have the same aerodynamic shape). Heavier bullets will decelerate less due to the higher inertia their increased weight gives them.

By way of example, a 180 grain round nose soft point .308 Winchester bullet has a BC of around .248, whereas more streamlined and heavier 190 grain spire point boat tail .308 bullets often have a BC exceeding .495. The higher the number, the more streamlined the bullet and the less it will decelerate over time. The lack of deceleration of the bullet gives it a flatter trajectory.

The ballistic coefficient of a bullet doesn’t only affect the deceleration of the round and therefore it’s drop, but it also affects how the bullet responds to cross winds while in flight. Once again we find that more aerodynamic bullets with a higher sectional density are less affected by cross winds when compared to less aerodynamic bullets with a lower sectional density. This explains in part why the common .22 LR cartridge is so affected by bullet drop and cross winds at ranges exceeding 50 yards.

Nosler CT Ballistic Sivertip .308 caliber 150 grain bullet. Note the rounded nose and very short boat tail, giving this bullet a low ballistic coefficient.

For long-range hunters, the ballistic coefficient of a bullet has an enormous effect on the energy a round has when it impacts the target. This is critical for proper performance of the round. For example, consider two Remington Core-Lokt 180 grain .308 bullets fired with a muzzle velocity of 2620 FPS and a muzzle energy of 2743 lb/ft. One bullet is a round nose soft point with a BC of .248. The other is a spire point with a BC of .383. The weight and sectional density of both rounds is the same. Out to 200 yards, we don’t see much difference in the performance of these two rounds, but at a range of only 300 yards we begin to see huge differences in their performances; the round nose bullet at this range only has a velocity of 1665 FPS, while the spire point bullet is still traveling at 1974 FPS. At 500 yards, the difference is even more pronounced with the velocity of the round point dropping to 1212 FPS while the spire point is still humming along at 1604 FPS. If these rounds were fired at an elk at a distance of 500 yards, the round nose would hit with only 587 lb/ft of energy, while the faster spitzer bullet would impact with a much greater 1028 lb/ft.

Do you need to worry about the ballistic coefficient of your round? Probably not. For the average shooter, the ballistic coefficient of a given round simply will not have a huge effect on them. For hunters targeting game between 50 and 250 yards, and target shooters plinking at similar ranges, the ballistic coefficient doesn’t have much time to affect the flight of the bullet. However, for long range and competition shooters, the importance of having a heavy streamlined bullet is of critical importance as they engage targets at 300 yards and beyond. The aerodynamic deceleration of a round increases exponentially with distance, so a bullet with a low BC will be affected much more at 600 yards when compared to a bullet with a high BC. The ability of a high BC round to overcome wind resistance as well be less affected by cross winds is critical to long range high-power competitors or hunters who hunt game at long ranges.