Riddle me this? Ballistic calc vs reality mismatch...

Stgraves260

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This is also not even remotely correct.

Your POI will change 0 inches with a 2.5 degree angle while the bullet is in supersonic flight which most centerfire rifles will be at 500. Unless in your hypothetical situation you’re using a .22 that is in subsonic at that range. The bullet is going too fast to care about two yards difference at this distance with the cartridges being talked about.
Actually it’s spot on. I put the chart in this discussion so people can use real numbers. Now if you or someone who see’s this and don’t know how to use the chart than it can’t help. I can understand the confusion. There is some really good info on some of these discussions. The only thang is when you get those internet//YouTube Snipers they will blow everything out of line. People get really short sometimes because they thank they know it all and can’t be taught something. You just have to let it roll off your back and move on. I wish you the best of luck.
 

Stgraves260

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Tota
Youtube TiborasausRex has a series of videos on this subject, very informative for understanding how the cosine factors into the equation.
Agree. If you thank his YouTube channel is good try taking one of his classes. It is pricey but well worth it. Not everyone can afford his class or one like it. So I just share a little of what I’ve learned from him and from the DMU. Rex gives very good info on his channel. There is grey areas on line and when someone try’s to correct them they get PO. One of the Thangs that’s not on the net is they don’t tell you that when using a cosine indicator you have to get your calculations from your zero. So before you dial up you have to get your calculations. From what I’ve seen in the field this is where a lot of people get very frustrated. Wishing you and your family good health during this pandemic going on.
 

Stgraves260

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That is a case by case thing as to what calculates what. Kestrel w/Applied ballistics will not only calculate the environments but it will calculate the density altitude change in the angle. The issue that most shooters probably run into is that once you have your correct drop for the angle, you need the true range for the wind. Again, your kestrel can do this automatically
I put that chart up for someone who was using a rangefinder that did not calculate for cosine. I thank someone was using a Vortex 5000 something. I read about it a little and it only adjust for cosine out to 800 yards. I have a first gen G7 and a Vectronix Rangefinder. Electronics fail so I got a back up. I use my mil dot master sometimes just so I stay fresh with it. I’m looking in to the new Kestrel 5700x. That and the Garmin 701 Foretrex. I also still like to use my Knights Armament ballistics calculator. It’s fast and easy when only going out to 2000 yards. When I made my 2300 yard shot that’s what I used. I have data in my sniper log that takes me a bit further than my electronics. So I had to pull that out also. All my electronics were failing at times so I had to go old school and use my calcform. I was in Brawley California visiting family and friends. We were shooting in the dessert. It was like 115-120 degrees out there. Had to set the rangefinders in the truck a few times and let them cool off. I was really surprised how well the G7 worked for the price. Overall I thank it held up pretty good. Some sand got into the buttons so I cleaned it off with a little bit of rubbing alcohol and everything was back to normal. Oh well, wishing you and the family good health during this pandemic. Good luck on your hunts this year.
 

BrentM

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I am really surprised people still use cosine and distance as the correction factor. Ballistic calculators use slope angle, distance, time of flight, atmospheric data, BC, etc to compute a shoot to correction. Rifleman rule of slope angle correction times distance is fine for short range and minute of deer but it is not precise enough for long range and small targets.
 

speedengineer

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Jan 31, 2020
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SE Michigan
Actually it’s spot on. I put the chart in this discussion so people can use real numbers. Now if you or someone who see’s this and don’t know how to use the chart than it can’t help. I can understand the confusion. There is some really good info on some of these discussions. The only thang is when you get those internet//YouTube Snipers they will blow everything out of line. People get really short sometimes because they thank they know it all and can’t be taught something. You just have to let it roll off your back and move on. I wish you the best of luck.

Stgraves,
While the chart you referenced isn't wrong (and is a helpful contribution to this discussion), you are indeed using it incorrectly. What that chart does is allows you to easily calculate the horizontal distance to the target, knowing the shot's inclination angle and line-of-sight distance.

This horizontal distance to the target is then typically used with a range card to get the values for bullet drop. Instead of looking up the bullet drop on the card for 500 yards line-of-sight, you'd look up the drop for 499.5 yards of horizontal distance (for 2.5 degrees inclination). For this case with such a small inclination angle, this would give pretty much the exact same answer for drop value.

Using a ballistic calculator with an input for the shooting angle is a more accurate solution, especially for high inclination angles. The old school quick n dirty chart method will get you close....but only if you use it correctly!!!!!
 

Stgraves260

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Stgraves,
While the chart you referenced isn't wrong (and is a helpful contribution to this discussion), you are indeed using it incorrectly. What that chart does is allows you to easily calculate the horizontal distance to the target, knowing the shot's inclination angle and line-of-sight distance.

This horizontal distance to the target is then typically used with a range card to get the values for bullet drop. Instead of looking up the bullet drop on the card for 500 yards line-of-sight, you'd look up the drop for 499.5 yards of horizontal distance (for 2.5 degrees inclination). For this case with such a small inclination angle, this would give pretty much the exact same answer for drop value.

Using a ballistic calculator with an input for the shooting angle is a more accurate solution, especially for high inclination angles. The old school quick n dirty chart method will get you close....but only if you use it correctly!!!!!
Take this discussion up with the DMU and our military snipers. Maybe they have it all wrong. Maybe you can set them straight. We love conflict.
 

entoptics

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Take this discussion up with the DMU and our military snipers. Maybe they have it all wrong. Maybe you can set them straight. We love conflict.
@Stgraves260
I want to believe that you're just not explaining yourself well, so could you please calculate the difference in drop for the following scenarios, however you would normally go about it?

Use the following parameters for both scenarios, or if you prefer, use parameters you're familiar with, and tell us what they are...

147 gr ELD-Match, G1 BC of 0.697 (G7 0.351)
2800 fps
1000 yds Line of Sight distance
60° F, 29.9 inHg (corrected), 2500 feet elevation, 40% humidity
1.75" sight height
100 yard zero

What drop in MOA or Mils would you dial for 0° incline, horizontal shot?
How many inches or centimeters of drop would that be?

What drop in MOA or Mils would you dial for a 25° incline, uphill shot?
How many inches or centimeters of drop would that be?
 

Stgraves260

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Sep 1, 2009
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605
If taking a 1,000 yard shot with a 25 degree angle regardless of shooting uphill or down hill the calculations will be the same. You must first refer to the chart and convert your degrees angle to cosine. 25 degrees is .906 cosine. So multiple your LOS ( 1000 yards ) by your cosine .906. Now this is where training kicks in. The number 6 in the cosine is higher than 5. So round your cosine up to .91 the equation will look like so.
1000 x .91 = 910 yards. This will be your shoot to range.
 

Stgraves260

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Joined
Sep 1, 2009
Messages
605
@Stgraves260
I want to believe that you're just not explaining yourself well, so could you please calculate the difference in drop for the following scenarios, however you would normally go about it?

Use the following parameters for both scenarios, or if you prefer, use parameters you're familiar with, and tell us what they are...

147 gr ELD-Match, G1 BC of 0.697 (G7 0.351)
2800 fps
1000 yds Line of Sight distance
60° F, 29.9 inHg (corrected), 2500 feet elevation, 40% humidity
1.75" sight height
100 yard zero

What drop in MOA or Mils would you dial for 0° incline, horizontal shot?
How many inches or centimeters of drop would that be?

What drop in MOA or Mils would you dial for a 25° incline, uphill shot?
How many inches or centimeters of drop would that be?
some pages have been replaced and up dated, some pages have scares I don’t wish to share but I keep as a reminder.
 

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Stgraves260

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This page has been replaced. It’s in good shape. I’m gonna take a breather for a while. Just give me a bit. I’ll get back with you as soon as I can.
 

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