January 18th, 2018

5 Degrees of Doom — The Danger of Over-Shooting the Berm

Gun Angle long range

In our Shooters’ Forum, there was an discussion about a range that was threatened with closure because rifle over-shoots were hitting a farm building over two miles from the firing line. One reader was skeptical of this, asking “how’s that possible — were these guys aiming at the stars?” Actually, you may be surprised. It doesn’t take much up-angle on a rifle to have a bullet land miles down-range. That’s why it’s so important that hunters and target shooters always orient their barrels in a safe direction (and angle). Shooters may not realize how much a small tilt of the barrel (above horizontal) can alter a bullet’s trajectory.

How many degrees of muzzle elevation do you think it would take to hit a barn at 3000 yards? Ten Degrees? Twenty Degrees? Actually the answer is much less — for a typical hunting cartridge, five to seven degrees of up-angle on the rifle is enough to create a trajectory that will have your bullet impacting at 3000 yards — that’s 1.7 miles away!

Gun Angle long range

Five degrees isn’t much at all. Look at the diagram above. The angle actually displayed for the up-tilted rifle is a true 5.07 degrees (above horizontal). Using JBM Ballistics, we calculated 5.07° as the angle that would produce a 3000-yard impact with a 185gr .30-caliber bullet launched at 2850 fps MV. That would be a moderate “book load” for a .300 Win Mag deer rifle.

Here’s how we derived the angle value. Using Litz-derived BCs for a 185gr Berger Hunting VLD launched at 2850 fps, the drop at 3000 yards is 304.1 MOA (Minutes of Angle), assuming a 100-yard zero. This was calculated using a G7 BC with the JBM Ballistics Program. There are 60 MOA for each 1 degree of Angle. Thus, 304.1 MOA equals 5.068 degrees. So, that means that if you tilt up your muzzle just slightly over five degrees, your 185gr bullet (2850 fps MV) will impact 3000 yards down-range.

Figuring Trajectories with Different Bullets and MVs
If the bullet travels slower, or if you shoot a bullet with a lower BC, the angle elevation required for a 3000-yard impact goes up, but the principle is the same. Let’s say you have a 168gr HPBT MatchKing launched at 2750 fps MV from a .308 Winchester. (That’s a typical tactical load.) With a 100-yard zero, the total drop is 440.1 MOA, or 7.335 degrees. That’s more up-tilt than our example above, but seven degrees is still not that much, when you consider how a rifle might be handled during a negligent discharge. Think about a hunter getting into position for a prone shot. If careless, he could easily touch off the trigger with a muzzle up-angle of 10 degrees or more. Even when shooting from the bench, there is the possibility of discharging a rifle before the gun is leveled, sending the shot over the berm and, potentially, thousands of yards down-range.

Hopefully this article has shown folks that a very small amount of barrel elevation can make a huge difference in your bullet’s trajectory, and where it eventually lands. Nobody wants to put holes in a distant neighbor’s house, or worse yet, have the shot cause injury. Let’s go back to our original example of a 185gr bullet with a MV of 2850 fps. According to JBM, this projectile will still be traveling 687 fps at 3000 yards, with 193.7 ft/lbs of retained energy at that distance. That’s more than enough energy to be deadly.

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February 8th, 2017

Wind Wisdom — Terrain Effects, Mirage, and Anomalies

Steven Blair F-Class Wind Tips

For you guys competing at the Berger SW Nationals this week, we’re repeating an excellent article by Steven Blair on wind reading. Steven, a top F-Class shooter, talks about mirage, topography effects, tail winds, and other subtle factors that can cause frustration for shooters. Steve explains that wind effects can be complex — there’s more going on than just velocity and angle. You need to notice things like berm locations and effects of temp changes over the course of the day.

Wind Reading Tips for Competitive Shooters
by Steven Blair, 2012 California State Long Range F-Open Champion

Assess the Terrain and How the Wind Will Interact with It
Before you begin a match, take a few minutes to look around the range at the terrain, any obstructions, range topography (berms and backstop), and trees, buildings or structures that could affect wind flow over the range. Imagine what might happen if the wind was from the left or right, headwind or tailwind. Depending upon the direction, significant effects may be seen on range. A head or tail wind may ripple across the berms, causing elevation changes, both high and low. A tall side berm, like the east side berm at Ben Avery, may cause turbulence when the wind comes from that direction. Blocking features might shield most of the wind but a break along the range can funnel strong gusts through the gap with no other indications. Take a few notes about the effects of different wind directions and refer to them if the prevailing direction changes. (Tip courtesy Tony Robertson.)

Steven Blair F-Class Wind Tips

Use a Spotting Scope, Even When Shooting a Scoped Rifle
A good spotting scope can “see” mirage much more clearly than even an expensive rifle scope. Take your spotting scope to the line and position it as sling shooters do, close enough to use without much movement. Focus the scope approximately 1/3 of the way down range or where the most significant wind effects are likely to occur. Take a quick look while waiting for pit service, glance at the flags and compare to your scope sight picture. I often see ambiguous indications at the target through the rifle scope, but see a clear indication of wind direction and speed through the spotting scope at the shorter distance. When shooting the Arizona Palma Championship at Ben Avery last weekend, I was scoring while the wind was coming from the east. Shooters up and down the line were out to the left, losing points. Mirage at the target looked moderate and the flags weren’t indicating strong wind. As I focused the spotting scope back, the mirage suddenly looked like it was flowing twice as fast around 500 yards than it was closer or farther. It wasn’t until I realized that the access road cut through the berm there that I understood what was happening. (Tip courtesy Gary Eliseo.)

Steven Blair F-Class Wind Tips

Don’t Over-React to Something That May Be an Anomaly
On ranges with sizable berms, a headwind or tailwind can cause significant elevation problems. It is generally not possible to see or predict when this will occur. When the conditions exist that cause elevation changes and other competitors are experiencing the same problem, the best strategy is to ignore it. Certainly, avoid shooting when the head or tail wind is gusting, the same as you would in a crosswind. But, if you react to random, range-induced elevation changes, the only likely result is to make it worse. Whether the problem is caused by range or ammunition, maintain your waterline hold until you have evidence that something has fundamentally changed.

Steven Blair F-Class Wind Tips

My .284 Shehane will usually require a click or two down during a string as the barrel warms. That is normal and manageable. But, if your shots are just bouncing up and down in the 10 ring, leave it alone. The same is also true of an occasional gust pushing a shot into the 9 ring. If the conditions have not changed and one shot just went out, it may be the result of a random occurrence that was not predictable. (Tip courtesy “School of Hard Knocks”.)

Adjust Spotting Scope Focus and Magnification as Needed to View Mirage vs. Target Details
In F-Class we only need to see mirage, spotters, and scoring disks. That does not take a lot of magnification. My scope is a Nikon 25-75x82mm ED. It is a superb scope for the money and makes it trivial to see minor variations in mirage. It is good to have the high magnification available, and it can always be reduced if necessary. I use different power settings for different situations.

Steven Blair F-Class Wind TipsSetting Magnification Levels
During a match, in very good viewing conditions, I set my spotting scope at 75X, full power. The mirage is more subtle in the morning and greater magnification is needed.

During a match with heavy mirage I set my spotting scope at about 40X. I have no problem seeing mirage, even at this magnification.

When practicing at 300 yards or closer I set my spotting scope at max power (75X) so I can see the little 6mm holes from my 6BR rifle. I usually need to focus back and forth between shots to see both bullet holes and mirage.

Steven Blair, 2012 California State Long Range F-Open Champion, has been shooting since childhood and competing for over 30 years. Before retiring, Steve spent 16 years in Engineering and IT with General Atomics. He has held Engineering and Marketing positions with several firearms companies and worked on projects from pistols to 155mm howitzers.

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February 1st, 2015

Over-Shooting the Berm — When a Mere 5 Degrees Can Be Deadly

In our Shooters’ Forum, there was an discussion about a range that was threatened with closure because rifle over-shoots were hitting a farm building over two miles from the firing line. One reader was skeptical of this, asking “how’s that possible — were these guys aiming at the stars?” Actually, you may be surprised. It doesn’t take much up-angle on a rifle to have a bullet land miles down-range. That’s why it’s so important that hunters and target shooters always orient their barrels in a safe direction (and angle). Shooters may not realize how much a small tilt of the barrel (above horizontal) can alter a bullet’s trajectory.

How many degrees of muzzle elevation do you think it would take to hit a barn at 3000 yards? Ten Degrees? Twenty Degrees? Actually the answer is much less — for a typical hunting cartridge, five to seven degrees of up-angle on the rifle is enough to create a trajectory that will have your bullet impacting at 3000 yards — that’s 1.7 miles away!

Five degrees isn’t much at all. Look at the diagram below. The angle actually displayed for the up-tilted rifle is a true 5.07 degrees (above horizontal). Using JBM Ballistics, we calculated 5.07° as the angle that would produce a 3000-yard impact with a 185gr .30-caliber bullet launched at 2850 fps MV. That would be a moderate “book load” for a .300 Win Mag deer rifle.

Gun Angle long range

Here’s how we derived the angle value. Using Litz-derived BCs for a 185gr Berger Hunting VLD launched at 2850 fps, the drop at 3000 yards is 304.1 MOA (Minutes of Angle), assuming a 100-yard zero. This was calculated using a G7 BC with the JBM Ballistics Program. There are 60 MOA for each 1 degree of Angle. Thus, 304.1 MOA equals 5.068 degrees. So, that means that if you tilt up your muzzle just slightly over five degrees, your 185gr bullet (2850 fps MV) will impact 3000 yards down-range.

Gun Angle long range

Figuring Trajectories with Different Bullets and MVs
If the bullet travels slower, or if you shoot a bullet with a lower BC, the angle elevation required for a 3000-yard impact goes up, but the principle is the same. Let’s say you have a 168gr HPBT MatchKing launched at 2750 fps MV from a .308 Winchester. (That’s a typical tactical load.) With a 100-yard zero, the total drop is 440.1 MOA, or 7.335 degrees. That’s more up-tilt than our example above, but seven degrees is still not that much, when you consider how a rifle might be handled during a negligent discharge. Think about a hunter getting into position for a prone shot. If careless, he could easily touch off the trigger with a muzzle up-angle of 10 degrees or more. Even when shooting from the bench, there is the possibility of discharging a rifle before the gun is leveled, sending the shot over the berm and, potentially, thousands of yards down-range.

Hopefully this article has shown folks that a very small amount of barrel elevation can make a huge difference in your bullet’s trajectory, and where it eventually lands. Nobody wants to put holes in a distant neighbor’s house, or worse yet, have the shot cause injury. Let’s go back to our original example of a 185gr bullet with a MV of 2850 fps. According to JBM, this projectile will still be traveling 687 fps at 3000 yards, with 193.7 ft/lbs of retained energy at that distance. That’s more than enough energy to be deadly.

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