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The Realities of Ballistic Coefficient
 by John Barsness

Sub-.27: Where The Action Is
 by Wayne van Zwoll

Short And Long Actions
 by John Barsness

Loads For The Long Shot
 by Wayne van Zwoll

Factors In Accuracy, Part One:
Rifles And Shooting

 by John Barsness

Annealing Cases
 by Ken Howell

Trophy Coues Deer In The Arizona Backcountry
 by Rick Bin

Factors In Accuracy, Part Two:
Handloading

 by John Barsness

Your Chronograph Can Tell You More
 by Ken Howell

Sonora: Where Giants Walk The Earth
 by Rick Bin

Getting The Most Out Of Your .30-06
 by John Barsness

Handloading for Long-Range Shooting
 by John Haviland

Cartridges and Bullets for Whitetails
 by John Barsness

Killer Buffalo
 by Ken Howell
(as told by Elgin Gates)

Rifle Brass
 by John Barsness

Big Eyes: Seeing Is Believing
 by Rick Bin

The Campfire Hardcore Hunting Backpack Review
 by Scott Reekers

Who Bombed Elmer Keith?
 by Ken Howell

Last Minute Muley
 by Rick Bin

Big Ivory
 by Ken Howell
(as told by Elgin Gates)

How I Killed a Bear
 by Charles Dudley Warner

A New Way To Hunt Lion
 by Ken Howell
(as told by Elgin Gates)

The .300 Winchester
 by Jack Steele

Choose the Right Backcountry Tent
 by Rick Bin

     
 
 
 
 
Advice from the experts ...

 
   
The Realities of Ballistic Coefficient
 by John Barsness

THE REALITIES OF BALLISTIC COEFFICIENT by John Barsness BEFORE COMPACT, affordable laser rangefinders became available to in the late 1990's, the primary emphasis for open-country hunting cartridges was high muzzle velocity, resulting in a flatter trajectory out to "normal" hunting ranges.  The definition of normal depended on the hunter: Some considered 300 yards a long shot, while others extended their maximum to 500 — though exactly how they guesstimated 500 yards was a valid question.  Still, somewhere between 300 and 500 was the practical limit, due not just to range-judging but the steep drop in trajectory of any bullet much beyond 400 yards, where a misjudgment of 50 yards could cause a complete miss of most varmints, and wound big game.

Lasers redefined not just normal shooting distances, but changed ballistic priorities.  The former emphasis on high muzzle velocity, whether with 50-grain bullets from a .22-250 for shooting prairie dogs or 130-grain bullets from a .270 for hunting deer, changed to an emphasis on ballistic coefficient.  Oh, there'd been some awareness of BC before then, but out to 400 yards muzzle velocity flattened trajectory more than BC, and a flat trajectory made hitting easier by minimizing the effect of errors in range-guessing.

But after hunters could actually KNOW the range, rather than guess, another "guessing" factory became more important, wind-drift.  Today tiny hand-held anemometers allow us to measure wind direction and velocity pretty precisely, and computerized ballistic programs tell us what effect both will have on our bullet.  But wind has a funny habit of changing direction and velocity over several hundred yards, and not just horizontally but vertically.

While a very high muzzle velocity minimizes wind-drift at "normal" ranges, as a bullet loses that initial velocity, wind-drift increases much faster at the longer ranges made possible by laser rangefinders.  Long-range target shooters had known this basic fact for decades, because they normally shoot at known distances anyway.  It took a while for the knowledge to sink in among hunters, but because of all the long-range hype eventually many hunters who don't really shoot all that far started thinking they needed to shoot heavier, sleeker bullets with high BC's, rather than lighter bullets with average BC's.


A flat trajectory often matters more on varmints, because they're smaller targets.

These days 500 yards is still a long shot even for hunters who dial the elevation turrets of their scopes, and for a good reason: Not many hunters actually get to practice much at ranges beyond 500, and those who do find making consistent first-round hits in any but the gentlest breezes difficult.  (Those long-range hunters who brag about making shots at 800+ yards sometimes use an old artillery technique called a "ranging shot," aiming at something a few yards from an animal to see where the bullet lands, then adjusting for the "real" shot.  But this works only if animals are so far away the sound of the shot doesn't spook them.)

As a result, around 500 yards is the practical limit for most hunters — and out to 500 yards, or even 600, ballistic coefficient doesn't always significantly outrank muzzle velocity in terms of wind-drift.  As an example, let's use a ballistic program to plot the trajectory and wind-drift of two bullets from the 6.5 Creedmoor, one of the more popular cartridges for such use, due to the high BC of 6.5mm bullets.

The trajectory of each bullet starts with sighting-in two inches high at 100 yards, because even many hunters who practice long-range shooting leave their scopes at a similar setting, just in case they need to take a quick "normal" shot out to 250-300 yards.  The trajectories are plotted with the scope centered 1.6 inches above the bore, for average fall environmental conditions during most of my hunting in Montana, but the differences between the trajectories would be similar with other scope heights and conditions.  Muzzle velocities are an average obtained from published data, and similar to what I've gotten from handloads in Creedmoors with 22-24 inch barrels, and the trajectory and wind drift numbers are rounded off to the nearest half-inch:

Berger Hunting VLD
130 gr., 2900 ft/sec
100 yds. 200 yds. 300 yds. 400 yds. 500 yds. 600 yds. 700 yds.
Trajectory+2.0 in.+1.0 in.-5.0 in.-16.5 in.-34.5 in.-59.5 in.-92.5 in.
Wind Drift2.0 in.4.0 in.8.0 in.13.0 in.19.0 in.27.5 in.
Retained Velocity1,985 ft/sec


Berger Hunting VLD
140 gr., 2750 ft/sec
100 yds. 200 yds. 300 yds. 400 yds. 500 yds. 600 yds. 700 yds.
Trajectory+2.0 in.+0.5 in.-6.5 in.-19.5 in.-40.0 in.-67.5 in.-102.5 in.
Wind Drift2.0 in.4.5 in.8.0 in.13.0 in.19.0 in.26.5 in.
Retained Velocity1,921 ft/sec

Note that out to 600 yards, wind drift is essentially identical.  The higher-BC 140-grain bullet only starts to drift less at 700 — by an inch, meaningless on anything larger than a prairie dog.

The trajectory of the 130 is obviously considerably flatter even at 700 yards.  This wouldn't matter to somebody dialing the range with the elevation turret, but would to a hunter who prefers to use a multi-point reticle.  Many do, because reticles work fine for big game out to 500 yards, and multi-point reticles are available in scopes about half the weight and size of the heavy-duty scopes preferred by serious dialers.

The same sort of "balance point" between high BC and high velocity exists in varmint cartridges, but the advantage often swings more to the velocity side due to a simple reason: A flat trajectory often matters more on varmints, because they're smaller targets.

While laser rangefinders continue to improve, the typical model used by a prairie dog shooter only provides a rather approximate range.  The laser isn't a tiny pinpoint of the same diameter regardless of range, but more like a flashlight's beam, becoming wider with range.  Consequently the reading we get isn't always from the dog, or even its mount, but often from a sagebrush or tiny cutbank 10-20 yards away.  This wouldn't matter when shooting at a deer, but can when shooting at a prairie dog only an inch or two wide.

As an example, a 40-grain Hornady V-Max started at 3750 ft/sec from a .204 Ruger drops about four inches between 200 and 300 yards, an average of less than half an inch every 10 yards.  A 75-grain Hornady V-Max started at 2850 ft/sec from a .223 Remington drops almost an inch per 10 yards from 200-300.  As a result, a ranging error of 20 yards isn't nearly as critical with the .204, and the two bullets both drift seven inches at 300 yards in a full-value 10 mph wind.  The advantage goes to the high-velocity .204.

Out at 400 to 500 yards the difference in drop is somewhat less, but the .204's bullets still drop at about 2/3 the rate of the .223's.  But the .223's bullets do start to drift a little less, about two inches at 400 yards and three inches at 500.  However, the .204 has another slight advantage, since its bullet arrives about 15% faster, slightly over 1/10th of a second.  This may not sound like much, but prairie dogs can move just enough in a tenth of second to cause a miss.  Let's call it a draw between the much faster .204 bullet and much higher-BC .223 bullet at 400-500 yards.  All of which is why I prefer the .204 for prairie dog shooting out to 500 yards, and only use much higher-BC bullets, whether from a .223 Remington or larger cartridge, beyond 500.

Since the percentage of hits goes way down beyond 500, even in calm conditions, I don't waste much ammo shooting at dogs over 500 yards away anymore.  Sometimes, however, the temptation is too much to resist, the reason a rifle chambered for a larger cartridge still gets taken along.

Our fathers and grandfathers tended to choose higher muzzle velocity rather than BC, because velocity made hitting easier at "normal," guessed-at ranges-while not realizing how much extra wind drift was affecting our bullets beyond even 200 yards.  But we shouldn't make a similar mistake by assuming higher ballistic coefficient always makes hitting easier at longer ranges.  Thanks to ballistic programs, the relationship between velocity and BC can be easily compared for different bullets in any cartridge — and should be, since the major point of laser rangefinders is to help make sure hits at any range.

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__________________________________________________

Ask John Barsness Questions About "THE REALITIES OF BALLISTIC COEFFICIENT"

John's new book MODERN HUNTING OPTICS and other great stuff can be ordered online at www.riflesandrecipes.com.

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