Ballistic Coefficients and the hunter


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It’s a matter of choosing the best bullet for the size of game, and terminal performance is far more important than ballistic coefficent. In open country where long shots are common, a bullet with a high ballistic coefficient driven at high velocity flattens the trajectory.

As most experienced shooters are well aware, the ballistic coefficient of a bullet is what governs its ability to overcome the resistance of air during flight. And the higher the bullet’s ballistic coefficient in a given calibre, the better it maintains its velocity downrange, and thus the flatter the trajectory. It should be obvious therefore, that the shape of the bullet plays an important part in determining ballistic coefficient. The sharper the point and more streamlined the bullet’s shape, the better its ability to overcome the friction of air. If the bullet’s nose is rounded or made flat, air resistance is increased, and it loses velocity at a more rapid rate.

Many techically-minded open country hunters think that they are obliged to use bullets with the highest possible ballistic coefficient in order to obtain the flattest trajectory and thus eliminate a lot of guesswork about bullet drop in the field. However, is this always the best choice? A more important consideration should be terminal performance.

A bullet should expand quickly to an optimum diameter, then stop or control that expansion to prevent what has become known as the “parachute effect.” It should hold together and not lose mass so that it will retain as much weightand momentum as possible to enhance penetration. Sounds simple, no? Now comes the hard part. The bullet must do this over a very wide range of impact velocities and penetrate a wide diversity of bone, tough hide, heavy muscles and other tissues.

Let’s take a look at the varying conditions that the hunter is likely to encounter.
In recent years the bullet picture has undergone considerable change as design technology has shown tremendous improvement. A boattail bullet always has a higher ballistic coefficient than a flat base of the same calibre and weight. So it would appear that the boattail is the best choice. However, while the taper-heel design is of benefit to the target shooter working at extreme ranges, it offers little advantage to the hunter unless he starts taking shots at distances over 500 metres – which is well beyondthe distance that’s considered to be sportsmanlike for the taking of big game.

In the past conventionally structured lead core bullets made it more difficult to lock the lead core and jacket together in a boattail than a flatbase. Consequently, core and jacket were prone to come apart in the animal, seriously limiting penetration. Hunters often tried to argue this point with me, but I’m a hunter who likes to see his bullets smash bone, plough on through masses of muscle andtissue, and destroy the vital organs before exiting the body cavity leaving a large exit hole through which the animal will hemorrhage and leave a distinct blood trail. If the bullet sheds its jacket this kind of performance simply isn’t going to happen. That old chestnut about bullets staying inside the game and expending all of their energy there, is a fallacy. It just doesn’t happen.

Happily this is no longer the case with all boattail bullets and hunters can now have their cake and eat it too. Some of the major manufacturers are making premium boattail bullets which feature controlled expansion via an extra heavy partition jacket and/or solid homogeneous copper or brass construction.

Barnes pioneered this with their solid copper X-bullet named for the distinctive X-shaped nose of the expanded bullet. The X- bullet was not without fouling problems, but proved tough enough to withstand high impact velocities without breaking up. Today it has evolved into the Triple Shock which has grooves in the shank of the bullet to reduce friction and fouling and provide a relief area for displaced copper to move when the bullet engraves the rifling. The TSX allows safe propellant charges one to two grains higher than the maximum loads listed for the X-Bullet accompanied by a slight increase in velocity.

There are situations where a sharp-pointed bullet with a lot of lead exposed at the nose isn’t the most desirable. This is because in many rifles, the nose of the bullet can be deformed as recoil causes the cartridges to slam forward against the front of the magazine box and thus affect the rifle’s zero. Once the soft nose is flattened, the bullet no longer shoots to the same point of aim as it did when the point was undamaged.

This problem was solved by designing bullets that have little or no lead exposed at the tip. These “protected point” designs eliminated the problem of point deformation, but also reduced their ballistic coefficient. Realistically, the difference was slight and didn’t make enough of a difference to the trajectory to worry about – at least not at reasonable hunting ranges.

It’s impossible to list all the good bullets, but a few bullets that offered ultimate penetration were Winchester’s Fail Safe, the Swift A-Frame and Trophy Bonded Bear Claw. However, some technically minded hunters were still bitching about their lower ballistic coefficient.

Ballisticians went to work and Nosler solved the problem very neatly by producing bullets which had a sharp polymer tip. The tip improves the capabilities of the traditional spitzer boattail bullet at longer ranges, and in the case of more recent designs like the Barnes Tipped Triple Shock X-Bullet ensures that the tip of the bullet will open and expand over a broader range of impact velocities than its predecessor.

This trend continued with Winchester’s E-Tip and Hornady’s similar relatively new lead-free GMX (gilding metal expanding) bullet. Both are composed of 95 percent copper, 5 percent zinc. and have a tapered heel. The GMX duplicates the SST’s flight path, since ballistic coefficients are almost identical.

Winchester also developed the XP3 (short for precision accuracy) which took hunting bullet technology “another step into the future.” A simplified version of the Fail Safe without the steel inserts that surround the front of the rear lead core, the XP3 is solid copper alloy up front but has a cavity at the rear containing a lead core. A translucent red polymer tip at the mouth of the nose cavity encourages the XP3 to expand at lower velocities.

The XP3 is built tough enough to smash through bone and penetrate as deeply on large game as the Fail Safe, but its front section is capable of greater and more reliable expansion on deer-size game at long range where impact velocity is relatively low.

The XP3 has a black Lubalox coating and its ballistic coefficients are some of the highest in the business. For instance, the .30/180gn is rated at .507 (the same as the Nosler Ballistic Tip); the .270/130gn rates .496 and the 7mm/160gn .500.

Barnes MR-X which preceded the XP3 by a few months is an offshoot of the TSX, maintaining the grooved shank and boattail but adding a polymer tip and tungsten rear core. It’s a bit like the back half of a Swift A-Frame or Partition. The end result is a bullet that’s more streamlined than the hollow-point TSX, while the heavier-than-lead tungsten core made it possible to shorten the bullet somewhat, although the polymer tip extends the length  of the nose, making the 180gn MRX the same length as the 180gn TSX.

Another premium big game bullet is Federal’s Trophy Bonded Tipped which offers a higher ballistic coefficient and more precisely controlled expansion than the previous Trophy Bonded Bear Claw. The TBTB bullet has a bright silver nickel coating and a neon orange translucent tip. Jacket and base are made of 95-5 gilding metal, and a modified rear shank has a series of concentric grooves cut around it, the size and number depending upon the calibre. The nose of the bullet is skived to initiate and control expansion. A smaller meplat and more pointed tip together with a boattail base and enhanced ogive contour gives an average 30 percent increase in ballistic coeffiecient over the older design.

Some bullets that were previously in the .400 range are now .500. This means a flatter trajectory, higher retained velocity, and more energy delivered downrange. The pure lead core is bonded to the jacket and a slightly smaller frontal diameter when fully expanded than the old TBBC, ensures deeper penetration while still producing a broad wound channel.

How do the different styles of bullets buck wind? If you’re shooting in a 10 mph crosswind, the difference is less than 4 inches between the least and the most wind drift – not really much to worry about when shooting at large animals.

In terms of bullet selection. always choose the bullet that you feel is going to do the best job under the conditions under which you’ll use it. High ballistic coefficients shouldn’t be the only thing to influence your choice because there’s very little difference between the new premium bullets. They all shoot flat and deliver what their makers promise: fine accuracy, dependable upset, a deadly mushroom, deep penetration and very high retained weight. That’s an impressive list of improvements over the old traditional cup and core bullets.

All right so we have a wide assortment of the best bullets in the world, but many readers are going to ask: Do I really need a costly premium bullet?” Good shot placement makes up for a whole lot of sins in bullet performance. External blow-up seldom occurs with today’s bullets unless you try to kill big game with a varmint bullet. If you use commonsense in matching a conventional bullet to calibre and game, you’ll not often be disappointed with the results.

But don’t get hung up on the idea that premium is absolutely necessary. Instead pay attention to what each bullet is designed to do and match that to your game and hunting conditions. If you are pushing the calibre envelope, using a 6mm or .25 on large deer, you want tough bullets. If you are shooting at long range you want accurate bullets that offer more rapid expansion. For average conditions on goats and pigs and small to medium deer using a standard calibre, a premium bullet is generally not needed amd you would do just as well sticking to the same old softpoints that have served you well for many years.

This article was first published in Sporting Shooter, October 2010.


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Nick Harvey

Nick Harvey is one of the world's most experienced and knowledgeable gun writers, a true legend of the business. He has been writing about firearms and hunting for more than 65 years, has published many books and uncounted articles, and has travelled the world to hunt and shoot. His reloading manuals are highly sought after, and his knowledge of the subject is unmatched. He has been Sporting Shooter's Gun Editor for longer than anyone can remember. Nick lives in rural NSW, Australia.

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