How Much “Juice” Do You Need for Bears?

by
posted on April 2, 2012
ot_mind_ah2015_fs.jpg (4)

Many of you will be hunting black bear this spring, some with a bow for the first time. One question I am asked a lot about bowhunting bears is, “How much kinetic energy (K.E.) do I really need to kill a black bear?

When hunting black bears, we know that the bears of, say, Quebec (where a very big bear is a 250-pounder), are not as large as those of Alaska or western Canada (where a big bear can weigh 500 pounds). Then there are the big bears in places like California and the Carolinas, where 600- to 800-pounders as big as grizzlies live. It will take more “juice” to run your arrow through the bigger bears. The question is, how much more?

Today, most of us are shooting compound bows that produce a raw arrow speed of somewhere between 250 and 280 fps, with some blasting over the 300 fps mark. Our arrows have lightened up as well. For example, I am currently shooting a 70-pound Hoyt Carbon Matrix, 28 ½-inch Beman ICS Hunter Pro 340 carbon shafts, and 100-grain Thunderheads. Total arrow weight is 407.9 grains, and raw arrow speed is chronographed at 281 fps. The initial K.E. generated at the shot is 71.53 ft./lbs. (To determine how much initial kinetic energy your own bow-and-arrow set-up has at the shot, the formula is which is arrow weight (mass) x velocity squared, divided by 450,240.)

Most experienced bear hunters I know believe that for averaged-sized bears taken at reasonable ranges—under 40 yards—the minimum initial K.E. number is just 40 ft./lbs. What’s it take to achieve that? A compound bow that sends a light 325-grain broadhead/arrow shaft combination downrange at 245 fps generates an initial K.E. of 41.57 ft./lbs. You can do that with some compounds set at as little as 40 pounds of draw weight. This should be considered the absolute minimum and used only in very controlled situations, such as stand hunting over bait. For larger bears—including grizzlies and Alaskan brown bears—I have always used the same setup I would choose when hunting elk. My Carbon Element setup fits this bill perfectly.

However, do not forget that K.E. is not everything in the penetration game. The other scientific principle involved in the penetration equation is called momentum. Momentum is defined as “a property of a moving body that determines the length of time required to bring it to rest when under the action of a constant force.” Bowhunters don’t consider momentum as much as K.E. for several reasons, mostly because as the speed of an object changes—and after the shot an arrow begins to decelerate, meaning that for every foot of flight it is traveling at a different speed than the foot before—it is too complicated to play with in a simple discussion. What you do need to know is that, all things being equal, heavier and denser objects traveling at the same speed as lighter objects will have greater momentum. That means it is more difficult to stop them, which means they will penetrate more deeply. An easy analogy here is visualizing both a golf ball and an egg smashing into your own ribs at the same speed. Which will hurt more? That’s why I choose medium-weight, and not ultralight, arrow shafts.

There is one other factor that seriously impacts penetration on game that has nothing to do with K.E. or momentum. This is broadhead blade sharpness. There is no question that broadheads with scalpel-sharp blades slice through hair, hide, muscle and internal organs much easier than dull blades, whose rough cutting edges drag, not slice.

Latest

LEDE Marlin Dark
LEDE Marlin Dark

Hardware Review: Marlin Model 1895 Dark

If you think lever-action rifles should only have walnut stocks and a blued-metal finish, then the new Marlin Dark series with its polymer buttstock and aluminum AR-esque handguard probably won’t be your thing. That’s a shame, because this recent offering in Marlin’s line of modernized, capable lever-action rifles has a lot going for it in terms of performance, functionality and fun.

ATN Shipping TICO LTV Thermal Clip-On

This thermal clip-on device is a huge night-time gear multiplier for hunters and observers, transforming any daytime scope into a thermal sight.

MidwayUSA Named Official Sponsor of the 2025 NRA Annual Meetings

Glock, Inc. is the Presenting Sponsor of the Freedom Experience on Saturday, April 26th

First Look: Montana Rifle Company Marshall Hunting Rifle

Montana Rifle Company (MRC) has announced its Marshall Hunting Rifle—a rifle the company bills as being 10,000 rounds in the making.

Spring Gobbler Gear Roundup

Mike Roux lays out his winter's turkey gear discoveries, just in time for spring gobbler season.

National 4-H Shooting Sports Signs on as Official +ONE Partner

The National 4-H Shooting Sports program has joined the +ONE Movement, a national mentorship initiative led by the National Shooting Sports Foundation (NSSF) that encourages peer-to-peer mentorship in the hunting and shooting sports.

Interests



Get the best of American Hunter delivered to your inbox.