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Thread: Slope compensation really usefull on rangefinders?

  1. #1

    Default Slope compensation really usefull on rangefinders?

    Due to a good sale at the local sportsman's warehouse I have seriously considered getting my first rangefinder. I've been wanting to get the rifleman model which compensates for slope, but they don't carry it. I'm trying to figure out if I should hold out for a deal on the rifleman model or take advantage of the sale on the non slope compensating model.

    The question is how important is the ability to compensate for slope? At 400 yards, it looks like a 30 degree angle would mean a differance of 6 inches if I undertand it correctly.

    This season, I have a caribou hunt on Adak planned as well as 1 or 2 trips to the Kenai for black bear. I'd like to get to Wy for Antelope, but that's not set in stone.

    So basically, it the slope compensation feature really useful given what I have planned?

  2. #2

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    Yup, an angle or slope compensator can be useful at longer ranges. Especially if you are shooting a medium velocity bullet.

    If you were shooting 180 gr bullet (BC .420) out of a 300 mag, @ 3000 fps, up or downhill, at a target 400 yds away straightline (slope distance), the horizontal distance would be 346 yds. The difference in drop between these ranges would be close to 8". Making a drop chart for diferrent ranges would be a good idea and you probably want to make 2 or 3 charts at different angles, such as 20, 30 and 40 degrees to interpolate from.

    For relatively close ranges (less than 500 yds) you only really need to compensate for this. However there is a little more to it than the differnce between the straightline slope distance and the horizontal distance. The differnce in your scope line of site and your bore also plays a factor which becomes imporatant at longer ranges and steeper angles. You'll need software to makes these calcs.

    Here is a good article on the subject

    http://www.longrangehunting.com/arti...e-shooting.php

    Here's an online ballistics calc you can play with...

    http://www.biggameinfo.com/index.asp...=/balcalc.ascx

  3. #3
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    Default Bowhunting

    I think angle compensating range finders may be more useful for bowhunters, in steep terrain than most rifle hunters.

    I'm sure slope comes into play with longer rifle shots, but there are very few people out there that can make 400 plus yard shots. I know I'm not one of them.

  4. #4

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    Quote Originally Posted by WIsam View Post
    This season, I have a caribou hunt on Adak planned as well as 1 or 2 trips to the Kenai for black bear. I'd like to get to Wy for Antelope, but that's not set in stone.

    So basically, it the slope compensation feature really useful given what I have planned?
    And BTW, I have hunted a lot of antelope and they are plains critters. I have never come across a significant angle shot on one. Dont know anything about Adak caribou.

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    Member jmg's Avatar
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    To echo Montana's comments, I use to live in Wyoming, and believe me, it is pretty unlikely that you'll take a shot at an antelope with any angle at all. It is flat flat flat and they are out in the wide open spaces.

    I am also in the process of looking at rangefinders and considering angle compensators. But for antelope in Wyoming - it might be a little flatter if you were hunting whitetails in Kansas, but not much.
    Never count your days, but rather, make all of your days count.

  6. #6

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    I ended up going with the 800 model with no slope compensation. Come to think of it, I've never taken a shot at an angle over 20 degrees and anything over 5 or ten degrees always seems to be pretty short range. Thanks for the help!

  7. #7

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    I picked up a Nikon Riflehunter 550 on a good buy this week. I like the idea of having the angle info. Anyone out there using this little toy? Suggestions, tips, things to watch for?

    Thanks!

  8. #8

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    As an FYI if you use BING to search for it and find it there are ways to get a 2-8% rebate via BING....

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    Quote Originally Posted by jeffin AK View Post
    I think angle compensating range finders may be more useful for bowhunters, in steep terrain than most rifle hunters.

    I'm sure slope comes into play with longer rifle shots, but there are very few people out there that can make 400 plus yard shots. I know I'm not one of them.
    I think that about sums it up. You can be off quite a bit with a rifle and still lob it in the right area. So if you have a good working understanding of how gravity affects shot angels I doubt it's really necesary for rifle hunters. With a bow 5 yards is HUGE!!! Even more so past 40 yards!

    Brett

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    If you know the yardage and can find the angle you can use cosine to calculate the distance from you to the game. I have included the percentage as a guide.

    If you are like me and have a compass my Silva Ranger model has a clinometer which tells me the approx angle of the slope for climbing and terrain analyst. By using the clinometer and pointing the edge of my compass on the animal I can get the approx angle and calculate the distance using the below formula.

    Angle 0 18 27 32 38 41 45 49 53
    Cosine 1 0.95 0.9 0.84 0.8 0.75 0.7 0.65 0.6


    YARDS X COSINE=ACTUAL YARDAGE TO USE IN THE FIELD TO MAKE SLOPE ADJUSTMENTS

    example: 500 yards at a 27 degree angle = .9 cosine value, or..
    500 x .9 = 450 yards

    As you can tell by the example the greater the distance the more precise you need to be in order to calculate the actual distance, regardless of angle up or down the distance will be shorter then if you were shooting on flat land.

    If you don’t use a chorny or have a really solid understanding of your bullets velocity and drop the above table will be of little value as there will be too many assumptions made to make the shot.

    For ballistics I use the below link it can create accurate drop table that you can use as a guide against real world testing. NOTHING BEATS TEST AT ACTUAL DISTANCES.
    http://www.jbmballistics.com/calculations/calculations.html

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