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why do shots drop more when shooting at a small incline at extreme range?

 
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  #15  
Old 08-02-2012, 09:22 PM
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Re: why do shots drop more when shooting at a small incline at extreme range?

I use Atrag it does not have a neg or pos slope function on it. As stated before I have shot the same range at 2000 plus yds from both ends. Uphill one way and downhill the other, the drops are the same.

I have not used the software you have and I don't feel qualified to argue with the solutions generated. I hope your software is FOS because if a 5 degree slope has that much difference in uphill vs downhill think what a much steeper angle would do.

I shot the 375 at 2500 yds and used the LOS distance, turned out the target was 4 to 5 degrees uphill. The center of the group was .2 mils high. I haven't shot any steep angles at ELR so I don't have any firsthand data.
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  #16  
Old 08-02-2012, 11:11 PM
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Re: why do shots drop more when shooting at a small incline at extreme range?

When I enter incline values greater than 7 degrees the drop decreases as expected, but when the bullet has slowed so much the downhill shot needs less holdover than uphill. I assume it is because gravity is helping the trajectory downhill and slowing the bullet shot uphill. The effect of gravity is almost invisible when comparing incline angles at supersonic speed, but at slower speeds, gravity changes things. look at it this way, the rifleman's rule is explained by the effect of gravity is diminished by the angle because gravity pulls down, not 90 degrees away from the line of sight. Well, when shooting uphill, gravity is not only pulling away from the line of sight but also pulling away from the direction of travel (slowing it down). When shooting downhill, gravity still pulls the same away from the line of sight ( assuming a directly inverted angle, like 6 and -6 degrees) but instead of pulling away from the direction of travel it is now benefitting the bullets speed (not slowing down as much). Another perspective is to look at shot at 45 degrees. Only half the force of gravity pulls away from the line of sight. How much effect can the other have, and at what point is the effect large enough to notice? It is so small that it is imperceptible when shooting a 375 cheytac at 2000. noted. Let me remind, this is only noticeable at much slower speeds, but here of guys doing amazing things with .308 winchester's and 175 smk. Maybe those guys have witnessed this?
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  #17  
Old 08-02-2012, 11:13 PM
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Re: why do shots drop more when shooting at a small incline at extreme range?

Maybe this is a complete waste of yours (and my) time. I'm going to go seat primers now. thanks for your input.
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  #18  
Old 08-03-2012, 10:38 AM
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Re: why do shots drop more when shooting at a small incline at extreme range?

There was a thread back in 2007 that discussed this issue. 6-5-07, Rifles Bullets Barrels Ballistics Forum, Uphill Downhill Corrections, Shawn Carlock.

Mr Perry Was contacted and asked about this issue, there is 12 pages of discussion and I have a headache. Look it up it's a pretty good read giving opinions on both sides of the issue.
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  #19  
Old 08-04-2012, 01:02 AM
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Re: why do shots drop more when shooting at a small incline at extreme range?

Thanks for sending me to that thread. Mr. Perry states "there is no difference between uphill and downhill." This seems true at reasonable distances. Like 1000 yards for my .223 and 2500 yards for your .375. Alot has happened in 5 years, and I am curious as to what his answer is now. He also said coriolis is negligble. really????? I always combine spin drift and coriolis into my calculations, and believe me, it makes a difference.
I guess the only thing to do now is try it for myself and see how my results compare with predictions.
1st step: Get my .223 shooting through transonic. This might include a corrected b.c. for a .224 x 1.2" projectile going sideways.
2nd step: get my s.d. in low single digits on a day with zero wind.
or revert to plan B, which is to accept the fact that I will never shoot small enough groups at such extreme distances as to be able to acquire usable data.
I'll let you know if i make it past step 1 after fire season has ended.
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  #20  
Old 08-04-2012, 01:48 AM
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Re: why do shots drop more when shooting at a small incline at extreme range?

Anyone serious about ELR shooting should verify computer generated predictions through actual field tests. The best way to settle the uphill/downhill question is to shoot your particular Rd at the distances you expect to encounter.

If you have a range where you can shoot steep angles from both ends you should do so, that will tell you which theory is correct at that distance.
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  #21  
Old 08-04-2012, 02:50 AM
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Re: why do shots drop more when shooting at a small incline at extreme range?

I believe I read you are using cutting edge. What b.c.(s) do you use? I have a 300 rum barrel sitting next to a rifle right now, but if that doesn't satisfy my desire, I will have to step up. I have had a hard time getting on board with solids. Do they perform as advertised?
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