Trajectory, Knock Down, Long Range Hunting Cartridges

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Trajectory, Meat Damage, and Knock-Down

The Practical Realities of Effective, Long Range Hunting Cartridges.

by Eben Brown
There are two areas of modern rifle opinion that I think are not correct:
1. That extra high velocity rifle cartridges are necessarily so much flatter shooting than medium velocity cartridges... the Myth of the so-called "500 Yard Cartridge" and,
2. That high velocity and energy are necessarily desirable at knocking down game... They aren't.
  What follows is an argument in favor of using medium velocities and heavy bullets for hunting...
We're going to look at the realities of bullet trajectory relative to velocity; Meat damage in relation to excessive energy; And Sectional Density as it relates to the Killing Power of a cartridge on big game.
  Practical, Useable Trajectory - Prior to the distance at which your scope is zeroed, the trajectory has to be flat enough so that you don't have to concern yourself with it and can aim right on at deer sized game. This means that... The trajectory should rise and fall no more than about 3" prior to sight zero.
  After sight zero, bullet drop accelerates. It's only predictable to the point where you can still estimate distance and a reasonable hold over to hit reliably... This is fundamentally true for all hunting cartridges.
  So... The trajectory should drop no more than about 12" at the furthest hunting shot after sight zero.
Yards 0 50 100 150 200 250 300 350 400 450 500
180gr 300 BRM 2300 fps Path -1.5 1.66 3.05 2.55 0.0 -4.76 -11.89 -21.6 -34.09 -49.6 -68.37
160gr 7mm BRM 2350 fps Path -1.55 1.56 2.93 2.46 0.0 -4.61 -11.56 -21.05 -33.30 -48.55 -67.08
140gr 6.5mm BRM 2400 fps Path -1.55 1.44 2.75 2.32 0.0 -4.35 -10.9 -19.84 -31.36 -45.69 -63.07
140gr 6.5mm Swede 2400 fps Path -1.5 1.44 2.75 2.32 0.0 -4.35 -10.9 -19.84 -31.36 -45.69 -63.07
180gr. 308 2600 fps Path -1.5 1.39 2.9 2.94 1.4 -1.84 -6.91 -13.94 -23.09 -34.52 -48.42
180gr. 30-06 2800 fps Path -1.5 1.03 2.38 2.45 1.18 -1.55 -5.84 -11.8 -19.55 -29.24 -41.02
180gr Win Mag 3100 fps Path -1.5 .86 2.26 2.63 1.9 0.0 -3.16 -7.66 -13.61 -21.1 -30.24
160gr STW 3300 fps Path -1.555 .87 2.39 2.98 2.59 1.15 -1.44 -5.25 -10.38 -16.91 -24.98
Gray = Shots Where Aiming is Beyond Practical, Useable Trajectory
BRM = 300, 7mm, 6.5mm BRM Cartridges were Zeroed at 200 Yards
Swede = 6.5X55 Swedish Mauser Zero 200 Yards
308 = .308 Winchester Zeroed for 225 Yards
30-06 = 30-06 Springfield Zeroed for 225 Yards,
Win Mag = 300 Winchester Magnum Zero 250 Yards
STW = 7mm Shooting Times Westerner Zero 275 Yards

Note: Trajectories Were Calculated with Sierra Infinity Software and Sierra Boat Tail Bullets

Energies that Cause Excessive Meat Damage -- In several successful years hunting with the medium velocity 6.5X55 Swedish Mauser and the 6.5mm BRM, I never saw an animal shot where it ran away... and yet damage to the meat was small. Medium velocity kills without ruining your meat.
   In contrast, I have observed that nearly every animal shot with a 30-06 exhibited excessive meat damage. Here's how we'll put a value on it: On two different occasions, deer shot at about 150 yards had their shoulders completely ruined where the bullet exited. The energy of a 30-06 bullet at 150 yards is 2561 ft/lbs. So... Bullet energies of more than 2500 ft/lbs. can produce excessive meat damage.
Yards 0 50 100 150 200 250 300 350 400 450 500
180gr 300 BRM 2300 fps Energy 2114 1967 1829 1698 1575 1459 1350 1248 1153 1064 982
160gr 7mm BRM 2350 fps Energy 1961 1817 1681 1553 1433 1321 1216 1118 1027 942 863
140gr 6.5mm BRM 2400 fps Energy 179000 1664 1546 1433 1328 1228 1133 1044 961 884 812
140gr 6.5mm Swede 2400 fps Energy 1790 1664 1546 1433 1328 1228 1133 1044 961 884 812
180gr. 308 2600 fps Energy 2701 2524 2355 2196 2045 1902 1767 1640 1520 1407 1302
180gr 30-06 2800 fps Energy 3133 2931 2741 2561 2391 2230 2077 1933 1796 1667 1546
180gr. Win Mag 3100 fps Energy 3840 3600 3373 3159 2955 2764 2584 2412 2250 2096 1950
160gr STW 3300 fps Energy 3868 3607 3362 3131 2913 2711 2524 2348 2181 2024 1876
Pink = Shots Causing Meat Damage  *  Gray = Shots Beyond Practical Trajectory

Note: Energies Were Calculated with Sierra Infinity Software and Sierra Boat Tail Bullets

  Sectional Densities and Velocities that Put Game Down -- The 6.5X55 Swedish Mauser is famous for being an extremely reliable game stopper. I believe the reason it works so well is a combination of two factors: High Sectional Density Bullets and Impact at Medium Range Velocites. 
  Here's a simple illustration of how it works:n of how it works:   If you shoot an aluminum pop can with a high velocity (800fps) air rifle, the soft lead pellet zips right through the can without disturbing it. Now, if you shoot that same can with a low velocity (non-expanding) BB gun at only 300-400 fps, it will make a dent, rip a hole through, and knock the can over. Medium velocity actually puts more whack into the target!
  BRM Cartridges:  The original Swedish Mauser 140 grain bullet has Sectional Density between .270 and .290 and Velocity UNDER 2,500 fps. These are the same characteristics of our BRM cartridges but, they're incorporated into a more efficient, modern cartridge design that's suited to modern powders and bullets.
Yards 0 50 100 150 200 250 300 350 400 450 500
180gr300 BRM .271 SD 2300 2218 2139 2061 1985 1910 1838 1767 1698 1632 1567
160gr 7mm BRM .283 SD 2350 2261 2175 2091 2009 1928 1850 1774 1700 1629 1559
140gr 6.5mm BRM .287 SD 2400 2314 2230 2147 2067 1988 1909 1833 1758 1686 1617
140gr 6.5mm Swede .287 SD 2400 2314 2230 2147 2067 1988 1909 1833 1758 1686 1617
180gr. 308 .271 SD 2600 2513 2427 2344 2262 2181 2103 2026 1950 1877 1805
180gr. 30-06 .271 SD 2800 2708 2619 2532 2446 2362 2280 2199 2120 2042 1966
180gr Win Mag .271 SD 3100 3001 2905 2811 2719 2630 2542 2457 2372 2290 2209
160gr STW .283 SD 3300 3186 3076 2969 2864 2762 2666 2571 2478 2387 2298
Green = Sectional Density and Velocity Similar to Swedish Mauser...GOOD!
Pink =Shots Causing Excessive Meat Damage... Bad!
Gray = Shots Where Aiming is Beyond Practical Trajectory... Bad!

Note: Velocities Were Calculated with Sierra Infinity Software and Sierra Boat Tail Bullets

Conclusions: Except for extreme situations, almost nobody needs a large magnum cartridge for big game hunting. Look at the green areas of the chart above to see the narrow range of suitability for the big magnums. Traditional cartridges like .308 Win and 30-06 are certainly more practical than magnums, but look at the green sections above... Even those cartridges aren't optimum for all hunting situations. On the other hand: Our BRM Cartridges Shine Under the Most Popular, Practical Hunting Situations!

To Read More About the BRM Cartridges, Click Here.
To Read About the Brown Model 97D Rifle, Click Here
To Read About Sierra Infinity Software Click Here
To Read More About Hunting Bullets Click Here

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