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Striper69 November 20th, 2021 03:27 AM

Long Distance Shooting
 
I'm planning on trying to shoot some deer from high on a Missouri River bluff. I used my range finder today and the deer will be 350 to 450 yards away. I'll be up pretty high as well. I'm going to zero my 300 Win Mag rifle at 6 inches above bulls eye at 100 yards. That should zero me at 300 yards approx. I want to get some practice in for next season because I hope to hunt Elk and Mule Deer in Montana on a friend's property.

My question is: will I have to compensate for the height I'm shooting from?

steves1911 November 20th, 2021 05:09 AM

Yes aim lower ..i dont have the exact formula right now but you need to know the cosine to be exact. At 300yds the diffrence wont be much unless its quite steep.

E.Shell November 20th, 2021 07:56 AM

Quote:

Originally Posted by steves1911 (Post 6482286)
Yes aim lower ..i dont have the exact formula right now but you need to know the cosine to be exact.

An uncorrected uphill/downhill shot will go high, because the horizontal distance isn't as great as the line-of-sight distance.
The cosine for your angle of departure/shot angle from horizontal is multiplied against the line-of-sight distance to arrive at a horizontal distance.
Elevation is calculated for the horizontal distance.
Wind is calculated for line-of sight distance.
Quote:

At 300yds the diffrence wont be much unless its quite steep.
This *probably* true, but that also depends on the rifle's trajectory curve. With a .22-250, it is minimal, with a .22 Long Rifle, it is drastic. Gotta do the math to know what YOU have to do.

davsco November 20th, 2021 08:28 AM

Some rangefinders compensate for angles, check yours

davsco November 20th, 2021 08:33 AM

Best answer is to put a target out there and see where you're actually hitting, then u know for sure.

lazarus November 20th, 2021 09:31 AM

Quote:

Originally Posted by davsco (Post 6482343)
Some rangefinders compensate for angles, check yours

And you’ll need one, ideally that does!

Even with 300wm the difference between 350yds and 450yds is pretty pronounced. Add in the difference for the vertical…

steves1911 November 20th, 2021 10:11 AM

Quote:

Originally Posted by davsco (Post 6482343)
Some rangefinders compensate for angles, check yours

This!!!
A good rangefinder is priceless especially hunting across steep terrain that has a way of making everything seem farther away then it really is.

Johnny5k November 20th, 2021 10:22 AM

Yep, It is just physics. I believe it is called the HCD or Horizontal Component Distance. So your drop is based on this number and not the total range. You can calculate this with trigonometry, using the range and any other value of the right triangle created, with the correct formula.

Range finders will use the angle to calculate HCD (mine will), but if you know the exact elevation difference, you can calculate that way as well.

Shooting at a 45 degree angle should give you a drop that is equal to about half of the normal drop, compared to the same distance to target on a flat range. Shooting up or down hill shouldn't matter much.

E.Shell November 20th, 2021 11:58 AM

Quote:

Originally Posted by Johnny5k (Post 6482456)
Yep, It is just physics geometry. I believe it is called the HCD or Horizontal Component Distance. So your drop is based on this number and not the total range. You can calculate this with trigonometry, using the range and any other value of the right triangle created, with the correct formula.

Range finders will use the angle to calculate HCD (mine will), but if you know the exact elevation difference, you can calculate that way as well.

Shooting at a 45 degree angle should give you a drop that is equal to about half 70% of the normal drop, compared to the same distance to target on a flat range. Shooting up or down hill shouldn't matter much.

Cleaned that up a little for you. 70% because the cosine for 45o is 0.707.

If you want to work this solution exactly, as needed for true long range, we would use the 'scope offset method', which uses come-up dope vs simple distance correction and takes into account the difference in vantage point between the scope and bore axes.

For hunting distances, the Rifleman's Rule I stated above gets us close enough.

Park ranger November 20th, 2021 12:10 PM

Put it in JBM ballistics to see the delta


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