September 28, 2021

Flatten The Curve for Hunting Deer – Part 1, by Behind The Counter

Do you remember how long it was supposed to take to “flatten the curve”? Weeks not years. In this article, it takes a second or less to flatten the curve.

To flatten the curve for hunting deer, we will follow the science. No masks required. This is primarily the science of external ballistics with a nod to terminal ballistics. The curve is the trajectory or arcing line of flight that a bullet takes when it leaves the muzzle of a firearm on its way to a down-range target. Because the barrel is pointed slightly above the line of sight, the bullet rises as it leaves the barrel at its muzzle velocity. As the friction of moving through air and gravity act on the bullet, velocity slows, and the bullet’s trajectory turns down. The decrease in velocity and the shape of the trajectory can be predicted taking account of variables like muzzle velocity, weight and shape of the bullet as well as the relative density of the air measured by height above sea level, local temperature, humidity, and barometric pressure.
This is important because:
• You get really excited, and your pulse races when you aim at a deer (buck fever).
• Your rifle hurts every time you pull the trigger (magnum rifle).
• It’s hard to get a deer to stand broadside at exactly 100 yards (real world).
• Your buddies at work set up a pool on the success (or failure) of your hunt. (ego)
• You spent a lot of money on gear for your deer hunt (anxiety).

Whether you accept the multiple challenges of a deer hunt with your personal defense rifle or your favorite hunting rifle, a basic understanding of the ballistics of the cartridge you are using will allow you to focus on only one point on a deer’s anatomy regardless whether your target is at 50 yards or 200 yards. Seeing a deer at 200 yards or less, knowing exactly where to aim, and knowing from practice with your rifle how to gently squeeze off a shot is what it takes to have a freezer full of venison. This basic concept is called Maximum Point Blank Range or MPBR. The distance in yards is derived from the external ballistic data for a given cartridge. We will come back to this very useful tool, below.

WHICH CARTRIDGE?

This is the second key decision you need to make. The first decision sets every other decision in play. Will you make a commitment to hunt deer this season or next?

My primary reason for making that commitment months ago was to have a very clear, purpose-driven goal to use my personal defense AR-15 to supplement my family’s food supply with my daily carry rifle. If that sounds like too much prepper talk, then ask yourself an important question. With your current gear and skills, could you take down a deer if you really needed the meat? With a conventional hunting rifle or your personal defense weapon? What do you need to do to prepare for that possibility?

Regardless how you answer these questions for yourself, I believe the whole process of planning and then executing a successful hunting trip is excellent preparation for what may be coming in the next several years. Yes, the Schumer is already hitting the fan, and the future is looking bleak.

THREE POPULAR DEER CARTRIDGES BY THE NUMBERS

To gain a basic understanding of external ballistics, let’s examine three popular deer cartridges.
The venerable .30-30 has been used very successfully as a deer cartridge since its introduction in 1895. In certain hunting conditions where short-range shots (100 yards or less) are the norm, it is still a popular choice.

Introduced in 2007 with long-range shooters as the target market, the benefits of the 6.5 Creedmoor were immediately apparent to hunters, especially those expecting shots at 200 yards or more. In a very short time, the 6.5 Creedmoor has eclipsed all of the Winchester Super Short Magnums as well as the 7mm Remington Magnum plus all the Remington Ultra Magnums and Short Action Ultra Magnums.

Our third comparison is the .243 Winchester introduced in 1955 and still very popular for good reasons as we will see from the numbers.

To compare these three cartridges, we will use data from Hornady factory ammo fired in a 24” test barrel to measure muzzle velocities and reduce muzzle velocity to adjust for the 22” barrels on the 6.5 and .243 bolt guns and for a 20” barrel on the .30-30 lever action. When looking at recoil, we will assume a scoped rifle weight of 7 lbs. for all three even though some gun makers offer rifles focused on reduced weight with a light, synthetic stock and a tapered barrel. Some 6.5 rifles feature longer and heavier barrels appealing to an extreme distance shooter as opposed to a weight-conscious hunter.

THE BASIC NUMBERS

Ballistic Chart Extract

Factor .30-30 6.5 CM .243
Bullet Weight (gr) 150 gr RN 143 gr ELD-X 100 gr SP
Ballistic Coefficient 0.185 0.625 0.405
Muzzle Velocity (fps) 2310 2660 2920
Muzzle Energy (ft lbs) 1902 2247 1893
Target Zero Range (yds) 100 100 100
100 yard Energy 1362 2048 1642
Drop at 200 yards (inches) -7.1 -3.9 -3.2
200 yard Energy (ft lbs) 953 1864 1431
Drop at 500 yards (inches) -135.5 -44.2 -48.8
Rifle weight (lbs) 7 7 7
Powder charge (gr) 35 41 41
Felt Recoil (ft lbs) 12.3 15.5 11.2
KEY BALLISTIC FACTORS

Shot Placement – The first and most important factor is not listed in any ballistic chart. That factor is shot placement – exactly where the bullet impacts the target. As a friend who is an NRA pistol instructor likes to remind his students: “A hit with a .22 is better than a miss with a .45.” So true!

Having plenty of experience with your chosen rifle is much more important than any paper statistic. When you are comfortable shooting in a variety of positions, can control your breathing even when excited by competition or a giant mule deer buck, and can always squeeze the trigger until it releases without your conscious effort, you are ready. Then, refine your shot placement and bullet selection using some of the factors listed below to aid in picking the right cartridge for you and the best bullet for that cartridge.
Muzzle Velocity – The speed of the bullet in feet per second (fps) when it exits the barrel.

For two bullets of the same weight and ballistic coefficient (BC), the bullet with the higher muzzle velocity (MV) will have a flatter trajectory. A higher muzzle velocity combined with a higher ballistic coefficient result in a flatter trajectory, an MPBR for a greater distance, and more kinetic energy at the target.

Ballistic Coefficient – This is a numeric measurement of a bullet’s efficiency at resisting drag from air as it travels through it. A higher BC or more efficient bullet shape loses velocity more slowly and is less subject to wind drift. It also means that a higher BC bullet will retain more of its kinetic energy simply because it has retained more velocity up to the point of impact. As a general rule, heavy-for-caliber bullets have a higher BC because of their longer and more aerodynamic shape (178 gr ELD-X .552 BC) as opposed to being short and fat (150 gr RN .186 BC) or in between with a less pointed nose and a flat base (150 gr SP .338 BC)).

Muzzle Energy – This measures ft lbs of energy imparted to the mass of the bullet as it leaves the muzzle. Retained energy drops as the bullet slows. Since the rate at which velocity declines is less for a higher BC bullets, the same concept applies to energy. Two bullets of the same weight launched from the muzzle at the same velocity will have the same muzzle energy, but the bullet with the higher BC will lose less velocity to air drag and less energy.

Bullet Design – The design of the bullet includes such elements as an expanding tip or a thicker copper jacket or a monolithic construction. The manufacturer’s choices greatly affect the size of the wound channel and the penetration distance. Based on my personal experience, I prefer a bullet construction that will allow the front to expand once the bullets has penetrated several inches causing more tissue damage but retain enough weight and energy to create an exit wound. To perform both tasks the bullet requires enough energy at impact to cause expansion and not lose all of the energy in the body cavity especially with a vital zone hit. Too much energy and a slight miss, for example hitting the shoulder, can still be lethal but destroy a lot of meat in the process.

APPLYING THE NUMBERS

The winner in the race for highest muzzle velocity goes to the .243 using the lightest bullet, a 100 gr bullet launched at 2920 fps, almost 10% faster than the 6.5’s 143 gr bullet. Muzzle energy measured in ft. lbs. is important but the retained energy at 200 yards is even more telling. The clear winner in this category is the 6.5 shooting a bullet with a high ballistic coefficient at nearly double the retained energy of the .30-30’s 150 gr bullet. The flattest shooting cartridge at 200 yards is the .243 which has only dropped 3.2” from a 100 yd zero compared to a 3.9” drop for the 6.5 and a 7.1” drop for the .30-30. With all three rifles sighted in so that they can hit the center of the target at 100 yards, the trajectory of the .30-30 has the big arc of a rainbow and would theoretically drop more than 11 feet at 500 yards whereas the 6.5 Creedmoor and .243 dop only 4 feet, a much flatter curve.

Some of the implications are very important. Let’s look at two cartridges that both use 100 gr bullets with the same shape. The muzzle velocity of Cartridge A is 1500 fps and Cartridge B is 1200 fps. We know that the bullet from A will arrive sooner than the same size bullet from B and will have more energy to impart to the target. Faster object of the same size has more energy. 500 ft lbs vs 320 ft lbs.

We also know that if Cartridge A weighs 100 gr and has a muzzle velocity of 1500 fps it will have more kinetic energy or retained energy than Cartridge B launching an 80 gr bullet at the same 1500 fps. A bigger object has more energy than a smaller object at the same speed. 500 ft lbs vs 400 ft lbs. (But, don’t overlook the fact that a higher BC may allow the lighter bullet would give up velocity and energy at a slower rate.

Part of the reason to care about muzzle velocity and muzzle energy is to be able to compare the amount of energy that a bullet still has at 100 yards or 200 yards. Using the chart above, let’s compare the .30-30 launching a 150 gr bullet at 2310 fps vs the .243 pushing a much smaller 100 gr bullet from the muzzle at 2920 fps. The muzzle energies are very close 1902 ft lbs vs 1893 ft lbs. But, take a look at 100 yards! The retained energy of the .30-30 has dropped because the heavier bullet with a much lower BC has slowed more quickly and energy has dropped to 1362 ft lbs. The faster-moving, lighter bullet from the .243 has energy of 1649 ft lbs and will rapidly outpace the .30-30 along the rest of the trajectory. There is much more to the “killing power” of any bullet than just energy, but it will help in understanding how a smaller bullet might be more lethal than one that is 50% larger.

Muzzle velocity is determined by the powder charge, the shape of the cartridge case which limits how big the powder charge can be, the type of primer, how efficient the powder is, how the bullet is seated (the amount of friction that has to be overcome at the case mouth and how much case capacity is reduced by the seating depth of the bullet), the type of rifling, rate of twist, the length of the barrel, and of course the size of the bullet. Muzzle velocity in conjunction with the ballistic coefficient are the primary factors that dictate the shape of the trajectory. The shape of the curve allows the prediction of the velocity at different points along the curve.

The profile of the bullet and the details of its construction influence how the energy is dissipated when a bullet impacts the target. Some bullets are designed to expand rapidly and significantly increase the size of the wound channel. Other designs, for example heavy bullets in large calibers for dangerous game, are intended to retain their shape to get maximum penetration.

Marketing hype from the gun manufacturers, gun store salesmen, and gun writers miss the real point when comparing these three excellent deer cartridges. The sales types are trying to push the newest or fastest or most powerful rifle. Instant success with the new death ray! No practice needed. Just hand over your credit card.

The simple truth is that all three of these cartridges work very well for taking down a deer. They do their job in different ways, and there are some trade-offs. A .30-30 lever gun is shorter and well-balanced but cannot use long, pointed bullets regardless the weight because of the tubular magazine. With the lightest weight bullet launched at the highest muzzle velocity, the .243 shoots very flat but retains enough down-range energy to still be very effective at 200 yards. The real benefit of the 6.5 Creedmoor is that its case profile, throat dimensions, and bullets were all designed for long-range shooting with relatively mild recoil. The 6.5 is also very effective on medium-size game like deer or antelope whether at 100 yards or extreme ranges.

MAXIMUM POINT BLANK RANGE

Fortunately, there is a very effective ballistic shortcut that works well for many hunters and especially deer hunters. This shortcut is called as MPBR or Maximum Point Blank Range. MPBR is the farthest distance at which you can hit a specific size target holding the crosshairs of your scope at the center of the target area, in this case the deer’s vital zone.

MPBR WITH AN 4” TARGET

.30-30 6.5 CM .243
near zero – yards 23 28 30
far zero -yards 153 199 209
MPBR – yards 177 233 244
100 yard height above center – inches 1.95 1.93 1.87

“Near Zero” and “Far Zero” refer to the fact that the trajectory’s arc will cross the line of sight twice. The first time as the arc rises, and the second time as the arc continues its downward path. With a near zero approximating 25 yards for all three of these cartridges, most of your range time could be spent sighting in your rifle at this distance and then checking to see if it is approximately 2” higher than dead center at 100 yards. With MPBR as the measure, both the 6.5 and .243 are clearly superior to the .30-30 with maximum ranges of 233 and 244 yards compared to 177 yards for the .30-30. At most practical ranges for the average shooter, all three will do the job.

The numbers are very straightforward. For both the .243 and the 6.5 Creedmoor, adjusting your scope so that your point of impact is 2” high at 100 yards, a center hold on a target at any range from 30 yards to 240 yards will impact inside a 4” diameter vital zone. There is no need to make a last-minute elevation adjustment on your scope or make a guess about how much hold-over is required. Spend your time getting your breathing under control and carefully squeezing the trigger.

Depending on the actual distance in the field, the bullet impact may be a little high, for example 2” higher at 100 yards than the center of the target, or it might be 2” lower at 230 yards for the Creedmoor or 240 yards for the .243. The story for the .30-30 helps explain its enduring popularity. The center hold will produce a solid hit from 23 yards to 177 yards. It worked in 1895 and still works today.

For this article, I used the MPBR Calculator from shooterscalculator.com adjusting for lower muzzle velocities from the shorter barrels of hunting rifles rather than use data from 24” test barrels. I went one step further and specified a target size of only 4” when in fact the actual size of the vital zone for relatively small doe is 7” to 8”. For a larger buck, the vital zone might be 10” or 11” in diameter.

The following table was generated using an 8” target zone. By comparing this chart with the one above, several things should be apparent still aiming for the exact same point on the deer’s body.

MPBR WITH AN 8” TARGET

.30-30 6.5 CM .243
near zero 17 21 23
far zero 200 256 275
MPBR 234 302 324
100 yard sight in 3.9 3.48 3.31

The key things to remember:

First, even with a .30-30, you can take a deer at any distance from zero to 234 yards aiming at the center of the vital zone. Focus on a careful shot. Don’t be intimidated by the distance.

Second, at ranges up to 300 yards, the flatter shooting cartridges are the most forgiving. In part, this explains the quest for the holy grail of screaming muzzle velocities. It also explains why the gun industry touted heavy recoil magnum rifles for so many years. They worked, but they wasted a lot of meat. Their heavy recoil also caused many hunters to flinch throwing their shot off center.

Third, don’t obsess over cartridge selection or rifle choice. Instead, practice shooting – different positions, different distances, different lighting conditions. Get your gear together, work out the logistics of your hunt, and build other skills like walking on rough terrain. Your secret confidence builders are MPBR and more trigger time.

“Aim small. Miss small.” One of the basic truisms for hunters and snipers. I prefer to practice with the notion that my vital zone target is only 4” in diameter. For most purposes, the reality is that you actually have a margin of error. That’s the reason to look at MPBR with an 8” target size and to compare to the 4” target. A slight flinch. A gust of wind. A twig snapping to alert a deer. A slight error in estimating distance. You are still covered. Aim small. It pays off.

The topics in Part Two (that will be presented tomorrow) deal with:
• The size, shape, and location of a deer’s vital zone,
• Legal, ethical, and practical considerations using your defense rifle for hunting,
• Other caliber options available for your AR-15 platform including .300 Blackout, 6.5 Grendel, 6.8 SPC, .224 Valkyrie, .22 Nosler, .350 Legend, and the new kid on the block: 6mm ARC.

Original Source