Rule of Thumb for Shooting Down Hill

[LRNut]

I haven't read all the replies, just the first page, but I agree that with only a 10 degree slope, this wasn't the cause of the miss. I bet the combination of the angle, aiming high on the animal to start with, and most importantly the altitude at which you were hunting really contributed. If your gun is zeroed at say 3000 feet elevation (not sure where Home is for you or what gun works used for the altitude) but let's say your turret was etched for say 3000 ft elevation and you were hunting at say 8000 feet, you would shoot roughly 3 additional inches high. So 1-2 inches for angle, 3 inches for elevation, and maybe 1-2 inches for temperatures and barametric pressure differences. I can't get more than 4-6 inches maximum error if it really was 10 degrees and not 20 degrees. They all add up. I recommend first going to a range at 500 yards or more, and shoot a 3 shot group at paper from a flat bench with a rock solid rest and make sure the turret is etched correctly for that given elevation and temperature etc conditions. Then print a dope sheet for those conditions and another dope sheet for the most extreme cold temperature and elevation you may be hunting in. And do that for a 0,10,20,and 30 degree shot. It will help you understand what kind of realistic error you may have in calculating your true dope in the field. That is why true long range hunters (greater than 600 yards) are less likely to etch their turrets and more likely to use a kestrel or other method for accounting for current conditions. Nothing wrong with etching your turrets, just have a good understanding of your limits. Using a rangefinder that can account for barometric pressure and shot angle will decrease your margin of error significantly for the etched turret setup, it you really should know what info is going into that little black box and how the output is determined. Again, mostly so you can know your limits.

All of what you wrote is true - my first thought (after scratching my head at the mention he held high on the shoulder) was a difference in altitude. My second thought: the real reason for the miss was a lack of practice at the range and conditions the shot was taken.

 

[Chadp82]

This is actually not true - time of flight is longer over the hypotenuse than than the horizontal leg, so the bullet will drop more than it would over the horizontal leg, but not as much as if the horizontal leg was as long as the hypotenuse.

To be as accurate and as fast as possible, get a rangefinder that does it all.

You are right, it's not exact.

I agree, range finder that give the compensation distance is easier. No need to pick at this any deeper.

 

[Shane Lindsey]

Range x Cosign of the angle x Cosign of the angle = Elevation Correction. Corrected.

I will add that angles need to be pretty extreme and distance great before most folks will be able to shoot the difference enough to matter. Top of mountain into the steep canyon...

 

[LRNut]

You are right, it's not exact.

I agree, range finder that give the compensation distance is easier. No need to pick at this any deeper.

At long range, at extreme angles, it isn't even close - you will miss if you use the horizontal distance. Go to JBM and see for yourself.

 

[Ward Thurman]

Hi everyone. Got back earlier this week from hunting CO 2nd rifle elk season in GMU 681. Took a cow early on but the bulls were scarce especially given the high winds. At dusk on Weds I had a 5 pt bull appear at 503 yards quartering to and since he was close (30 yds from) a fence (private ranch on the other side), I aimed high on the shoulder (after dialing my Gunwerks 7mm RM shooting 168 gr VLDs to 500 yds) & gently squeezed. My spotter called the shot right over his back. The bull promptly moved off into the timber (not presenting another shot), jumped the fence and minutes later was shot on that private ranch. One more data point, the bull was 10 degrees downhill from me and I had a solid but not perfect rest.

My question is, did I just muff the shot high or should I have dialed a shorter distance on the Viper PST? Do you have a rule of thumb for shooting at high or low angles, like "for 10 degrees, reduce the distance by 10%"?
Thanks for your time & advice!

All the gun writers and experts are usually wrong on this subject. I didn't know this until I took physics in college. I don't care what kind of math and BS these guys spew forth; they are wrong. It is simple: When shooting downhill (it must be quite steep though to have much of an affect) aim low. The component of gravity trying to pull the bullet down to the ground is partially working WITH the bullet so it has the effect of not slowing the bullet as much. While shooting uphill (again steep slopes) you will need to aim high as the force of gravity will be pulling back against the bullet slowing it more. And if anyone says otherwise, ask them this; why did armies in the days before aircraft always try to gain the high ground? Pretty simple.

 

[Ward Thurman]

You have a Gunwerks gun and a rangefinder that doesn't compensate for angles ? Time to upgrade that very small but important piece of gear my friend. Do you have a yardage type elevation turret or a standard MOA one and how were you calculating altitude ?
Misses happen and you are learning from it. Congratulations on your cow !
BTW a steep angle like on a 3 4 5 right triangle ( substitute 300 400 500 yards) you would bee ranging 500 yards but the shoot to yardage would be 400 yards.View attachment 311403

This is totally wrong. The range is still 500 yards. The distance the bullet is traveling is 500 yards, not 400. If you aim low shooting uphill here YOU WILL MISS.

 

[Shane Lindsey]

This is totally wrong. The range is still 500 yards. The distance the bullet is traveling is 500 yards, not 400. If you aim low shooting uphill here YOU WILL MISS.

Have you actually tested what you are saying? If not, you should actually shoot this and confirm what you are saying is in fact INACCURATE.

Gravity only affects straight/horizontal line distance. Up hill/Down hill makes no difference.

 

[LRNut]

This is totally wrong. The range is still 500 yards. The distance the bullet is traveling is 500 yards, not 400. If you aim low shooting uphill here YOU WILL MISS.

Have you actually tested what you are saying? If not, you should actually shoot this and confirm what you are saying is in fact INACCURATE.

Gravity only affects straight/horizontal line distance. Up hill/Down hill makes no difference.

The bullet is traveling 500 yards; the time of flight is longer than if it was traveling 400. However, the gravity vector is lower than if it was 500 yards over a horizontal distance, so you do hit lower at 500 firing uphill/downhill, but if you hold for the horizontal drop at 400, you will hit low.

 

[Shane Lindsey]

500 yards x cos of the measured angle = elevation correction applied to turret. Corrected.

Archery equipment will display this pretty well. Good lasers have a correction in them. If you lase the target at not the normal setting, then do it again with the angular correction added. It will show you there is a difference.

Only way to know for sure is to shoot extreme angles. I have where a lack of correction will lead to a whiff...

 

[LRNut]

500 yards x cos of the measured angle x cos of measured angle = elevation correction applied to turret.

Your formula makes no sense; say your angle is 45 deg. The COS of 45 is .707. 500x.707x.707=250.

 

[Shane Lindsey]

Your formula makes no sense; say your angle is 45 deg. The COS of 45 is .707. 500x.707x.707=250.

You are correct. Multiply the Cosine twice if a vertical mil reading is taken for range estimation, where the slight angle needs compensation.

I corrected the earlier.

 

[LRNut]

Ag

You are correct. Multiply the Cosine twice if a vertical mil reading is taken for range estimation, where the slight angle needs compensation.

I corrected the earlier.

Like I have said earlier, the drop of the bullet fired at an angle is NOT the same as the drop over the corresponding horizontal distance. At moderate ranges it is close but at severe angles and long ranges, it is not.

This thread should be a pretty good indicator that those who still use a COSINE indicator should just toss them in the trash and get either a SIG or BR7 rangefinder.

 

[Shane Lindsey]

Ag

Like I have said earlier, the drop of the bullet fired at an angle is NOT the same as the drop over the corresponding horizontal distance. At moderate ranges it is close but at severe angles and long ranges, it is not.

This thread should be a pretty good indicator that those who still use a COSINE indicator should just toss them in the trash and get either a SIG or BR7 rangefinder.

Yeh, but batteries fail, gear breaks, goes in the drink, etc. Good to have/know alternate options.

 

[FEENIX]

For what it is worth ...