Rule of Thumb for Shooting Down Hill

[HappyGVM]

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!

 

[dfanonymous]

There IS a rule of thumb for for angled shooting. Aim low. For up hill OR down hill. It doesn't matter.

That's the rule if you don't want to get into the weeds.

If you do want to get into the weeds I recommend you get familiar with rifleman's rule, and the improved rifleman's rule. Or you can know none of it, get a kestrel and be sure to know what data to use, and you'll be just as good.

 

[338 dude]

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!

I don't know a rule of thumb or formula but angles up or down will result in a high hit,If you know the cosine angle most apps would correct for that

 

[Bravo 4]

10 degrees is a cosine of like .98 (or 98% of the lazed range), multiply the range (or drop data) by that for a shoot-to or flat ground distance. That would equate to only a couple inches of difference, you muffed the shot! Download a cosine chart or better yet get a range finder with angle compensation.
P.S.: congratulations on your cow!

 

[stonehands1]

Here's the chart for angle compensation. Calibrate an angle finder on your phone works good for getting angle

 

[dfanonymous]

If you want a "formula" then it's the cosine of the slope angle multiplied by the true range, and dial for that. This doesn't take into account elevation loss or gain. There are better ways to calculate it.
Like:
DROP*[1 - COS(A)] to get your overshot distance (d).

Some Rigid Trajectory Theory is applied next by dividing your overshoot distance: d*1000 by the slant range R….(d/R) you get you output in mils.

Hunters need not know, but I'll post for the sake of accuracy.

 

[Zen Archery]

There IS a rule of thumb for for angled shooting. Aim low. For up hill OR down hill. It doesn't matter.

THIS.... 3D Archery taught me this lesson the hard way!!!

 

[sp6x6]

ACI mounts on rifle.I have several ,dont really use but could as my Sig figures it.Had before that or as fail safe.

 

[Reelamin]

Sucks for sure and don't beat yourself up too much. It all depends on where you were holding on the animal, and how far over its back you estimated it went. That would be dang hard to tell since the impact would have been a long ways away if the slope continued. Also, your rifles pure and your real world rifles accuracy potential at 503 yards in that situation. You should have been aiming for a 495 yard shot. Using 3000fps and general atmospheric conditions 50 degrees at 5000 feet less than 2" of less drop in those 8 yards. I wont call it a "Duff" unless I know the pure accuracy of your rifle at 500 and where you held.

 

[Wedgy]

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.

 

[dogz]

Depends on how steep of an angle you needed to hold low for sure. I'd say that the actual ranges was more like 400-417- give or take.

 

[Chadp82]

The geometry is right triangle geometry. Your actual shot distance is the hypotenuse but the distance you need to use for the shot is the horizontal leg distance. A few different ways to calculate the horizontal from the hypotenuse. This is why range finders that do this for you call it the horizontal compensated distance or something similar.

The reason it's a horizontal distance for bullet drop is a physics problem which I won't bore anyone with.

All that fancy college math and I use nothing more than geometry now in my day to day work.

 

[ndking1126]

Jbmballistics allows you to put in the angle and you can see how much it varies from a level shot without having to do math. Run the numbers at level, hit the back button and change it to 10 degrees and run it again. I've never tested their numbers when shooting steep angles, but with flat shots they've always been very close.

Update: I threw I some generic but probably close to accurate numbers and the difference in impact with a 10* angle was .9" at 500 yards. I can't imagine that was enough to cause the miss on its own.

 

[MagnumManiac]

Rule of thumb for uphill or downhill shots is to aim in the bottom third of HAIR. Never aim for AIR.
Unless the shot is almost vertically up or down, you always aim LOW.
I lost an animal due to not aiming low enough because in my haste I forgot to aim low. Animal was taken some months later and the hit that didn't take him had healed over. Was hit between the shoulder and spine without doing any real damage. Was a Nosler 225g Accubond out of a 338WM at roughly 225mtrs.

Cheers.