Rule of Thumb for Shooting Down Hill

[LRNut]

I watched the first video (most of it) but from what I saw it is WRONG, because the TOF of a bullet going 500 yards (his example) is longer than one going 250 yards. Just because some guy puts out a YouTube video doesn't mean he knows what he is talking about.

Let's says you range a deer at 577 yards at a 30 deg angle. According to the math above, the true distance is 500 yards, and you hold there. Great; JBM Ballistics says you will hit 33.9 inches low at 500 yards (195 7mm Berger at 2950 zeroed at 200). However, if you put in the exact conditions, 577 yards with a 30 deg angle, you are 40.5 inches low at 577, which is nearly 7 inches different! Granted, it still hits higher than if fired over flat ground (that drop would be 50.8 inches), but if you use the equivalent horizontal range at steep angles and/or long range, you will miss.

 

[dfanonymous]

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.

You're arguing too hard and using to many words to make people understand that you need to aim low.

To be fair, it's a physics question. Which is why I posted a physics equation on the first page. Lastly it depends on the type of precision you need.

Regular rifleman's rule is probably fine for most people here. It's already been mentioned that you will KNOW you need to make a correction to your slope dope when you are a **nt hair away from rolling head over heels in your shooting position and how rare it is to be in that position specifically at ELR ranges.

Improved Rifeman will work for most other people…including most non ELR competitors…in all other cases, your kestrel ab or similar software will do the trick.

 

[Stgraves260]

Yep as they have stated aim low. I also just got back from CO for mullies.
Shot was 258 yards very steep uphill. I have a zero if 100 yards and didn't have time to check angle. Thanks to the great wisdom on this sight I knew that I just held dead on knowing it would hit high if at 100 and be very close at my range bullet impacted exactly where I was aiming which on a flat plan would be low at that distance.

At 258 yards, even at a 50 degree angle your bullet impact is barely 1" difference.

 

[greenejc]

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.

Actually the horizontal leg distance is what you use. That's because an angled (up or down, it doesn't matter) shot gets an assist from gravity. The reason there are charts is because that assist is constant, due to the gravitic constant. The military uses this constant to determine maximum ordinates for artillery, rockets and mortars. In world War I, they used tables and bullet weight/B.C. to determine what angle to fire massed machineguns at targets such as road intersections and other open targets. They could put massed fires on targets as far out as 4500 yards. It was quite effective. The angle off of horizontal effectively flattens the trajectory.

 

[Stgraves260]

You're going to want to reread what I said before you try to correct me on what "the math is.."

I reread what you said. You said aim low Whether you shoot uphill or downhill. Correct? That's why I sent the corrected info. If your target is at 250 ish yards or so even at a 50 degree angle. Your talking not even a 1" difference in drop. I do realize things get misinterpreted on here sometime and I try and be understanding. When someone ask a question I try and answer it the best I can. I try not to leave out and details. I don't want someone shooting at animals at any distance and always aiming under the gut because the so called rule of thumb is always aim low when shooting up hill or down hill. They need to know the math and what's all involved before squeezing the trigger.

 

[greenejc]

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.

That is correct. And if you have a target up or down hill you do shoot low because the slope causes the trajectory to be flatter.

 

[dfanonymous]

I reread what you said. You said aim low Whether you shoot uphill or downhill. Correct? That's why I sent the corrected info. If your target is at 250 ish yards or so even at a 50 degree angle. Your talking not even a 1" difference in drop. I do realize things get misinterpreted on here sometime and I try and be understanding. When someone ask a question I try and answer it the best I can. I try not to leave out and details. I don't want someone shooting at animals at any distance and always aiming under the gut because the so called rule of them is always aim low when shooting up hill or down hill. They need to know the math and what's all involved before squeezing the trigger.

Yet it's still corrected if you aim low. In your case specifically 1 inch low in that specific case. But that's not what you corrected…you said " No, the math stays the same weather you aim low or high."
There was no correction in your statement. I specifically mentioned that. Despite the fact in physics that's not a 100% true, the simple concept of effect after adding drag into the equation is negligible it's not worth mentioning.

 

[greenejc]

I watched the first video (most of it) but from what I saw it is WRONG, because the TOF of a bullet going 500 yards (his example) is longer than one going 250 yards. Just because some guy puts out a YouTube video doesn't mean he knows what he is talking about.

Let's says you range a deer at 577 yards at a 30 deg angle. According to the math above, the true distance is 500 yards, and you hold there. Great; JBM Ballistics says you will hit 33.9 inches low at 500 yards (195 7mm Berger at 2950 zeroed at 200). However, if you put in the exact conditions, 577 yards with a 30 deg angle, you are 40.5 inches low at 577, which is nearly 7 inches different! Granted, it still hits higher than if fired over flat ground (that drop would be 50.8 inches), but if you use the equivalent horizontal range at steep angles and/or long range, you will miss.

That's why the Army uses tables for this. But the question was 'was it me?' Since a 10 degree slope got him a maximum of 2" less drop at 503 yards, and he held high 3rd on the elk, the answer is partly. His shot group dispersion and the not-quite-perfect rest probably helped him miss high, but so would dispersion over the distance and a high point of aim. I like JBM's calculator, and have found it to be pretty accurate, along with Shooter's Calculator and the Shepherd Scope calculator used on the Shepherd website. They're all an approximation. That's why I test loads at distance under hunting conditions. If I have a range, I can get very accurate at distance just from having shot angles and at altitude with the weapons and loads I use. But past about 500 yards, the shot dispersion (1" 5 shot groups are generally 5" groups at 500 yards for example) will mask the difference in trajectory, so I always shoot center-mass when in doubt.

 

[FEENIX]

I watched the first video (most of it) but from what I saw it is WRONG, because the TOF of a bullet going 500 yards (his example) is longer than one going 250 yards. Just because some guy puts out a YouTube video doesn't mean he knows what he is talking about.

Let's says you range a deer at 577 yards at a 30 deg angle. According to the math above, the true distance is 500 yards, and you hold there. Great; JBM Ballistics says you will hit 33.9 inches low at 500 yards (195 7mm Berger at 2950 zeroed at 200). However, if you put in the exact conditions, 577 yards with a 30 deg angle, you are 40.5 inches low at 577, which is nearly 7 inches different! Granted, it still hits higher than if fired over flat ground (that drop would be 50.8 inches), but if you use the equivalent horizontal range at steep angles and/or long range, you will miss.

If you are referring to the video link I provided, please feel free to correct Ryan Cleckner on the actual video. I am sure he will be more than happy to discuss it with you.

 

[Stgraves260]

See if this helps anyone. This is the cal form the military uses. After the military released this info to civilians that's when you started seeing all the advanced range finders with applied ballistics and all these shooting schools open up.

 

[Stgraves260]

That is correct. And if you have a target up or down hill you do shoot low because the slope causes the trajectory to be flatter.

Yes sir

 

[greenejc]

View attachment 311915
See if this helps anyone. This is the cal form the military uses. After the military released this info to civilians that's when you started seeing all the advanced range finders with applied ballistics and all these shooting schools open up.

That info and the fact that the teachers at the schools are mostly retired snipers, and very familiar with and practiced at shooting at distances past 1,000 yards. When firing artillery or Naval guns you have to use tables like this. Even then, a spotter adjusts the first impact, because even if the data is good, there are variations which result in the impact being out by as much as 500 meters at 12,000 meters. For line of site ordinance, differences in conditions at the half-way point of the flight of the bullet will effect where it strikes, but for it to do so, ranges must be fairly extreme or conditions must be extreme. Thanks for the chart. Its been a while since I've seen one. Brings back memories.

 

[dfanonymous]

View attachment 311915
See if this helps anyone. This is the cal form the military uses. After the military released this info to civilians that's when you started seeing all the advanced range finders with applied ballistics and all these shooting schools open up.

No it's not. We learn hard dope then software. We use kestrels and actual drop. Forms similar to this haven't been used in a few decades. Even the TDS recon was a thing prior to the kestrels.

There is a time and place to sweat the small stuff. This is exactly more oriented to toward ordnance.

 

[Stgraves260]

That info and the fact that the teachers at the schools are mostly retired snipers, and very familiar with and practiced at shooting at distances past 1,000 yards. When firing artillery or Naval guns you have to use tables like this. Even then, a spotter adjusts the first impact, because even if the data is good, there are variations which result in the impact being out by as much as 500 meters at 12,000 meters. For line of site ordinance, differences in conditions at the half-way point of the flight of the bullet will effect where it strikes, but for it to do so, ranges must be fairly extreme or conditions must be extreme. Thanks for the chart. Its been a while since I've seen one. Brings back memories.

Yes sir correct and you are welcome . I was in the Army myself.