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Sighting in from a shorter distance than required

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 13:55
Beers78n9 View Drop Down
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I am gong to sight in my hunting this weekend. The issue I have is that I shoot a .300WSM, my scope (Nikon Buckmaster 3x9 w/ BDC reticle) needs to be zeroed at 200 yds and the range we are going to is only 100 yds. What should I treat as zero at that short of a distance? I am thinking .5 to 1 inch high at 100yds. Am I correct?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 13:57
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Chief Sackscratch

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Sounds about right.
 
  If you have access to the load data you can always plug it into a ballistics calculator and it will give youa rough estimate of the drop from 100-200 yds, then just site in that much high at 100.
 
Another thing, just because its a BDC reticle that says to site in at 200 and your distances should be on doesn't mean they will.  There is no substitute for actually putting rounds downrange and confirming bullet point of impact.  You should never take a shot at game if you haven't shot that distance on the range to verify. (IMO)


Edited by SVT_Tactical - September/21/2010 at 13:59
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 15:50
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Thank you.
 
I did sight in last year at 200 and took several shots at 300 (I'm in Western Washington and the possibility of a shot over 300 isn't very likely) and was dialed. So as long as I'm still close at 200 I am confident it will be fine.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 15:53
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Chief Sackscratch

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sounds good.  Good luck and happy hunting.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 15:59
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I dont know much but there are a lot of things to consider.  I had the same issue the other day as the range I went to was only a 50 yard range and I wanted to sight in my new scope. The range is free so it was worth it to get the kinks worked out before I go to the nice pay range we have at Atterbury. Anyway I sighted my rifle in for 2 inches high at 50 yards. My groupings at 50 had all three bullets touching. .612 was my estimate. Most of what I have read shows that if you double the distance than generally your group size will double (neglecting wind) so I have roughly a 1.2 inch group at 100 yards. At least thats what it might be in theory. Wont know until I actually go shoot at 100 yards.  On another note the army sights in there m4 rifles at 25 meters to be dead on zero. They are then dead on zero at 300 meters. This is due to the offset of the sight from the barrely on the m4 etc.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 18:21
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Depending on the load, 1-2 inches high @ 100 is probably going to be about right. Without going into details, if you're staying at 300 yards or less, then you're going to have a drop of about 6" from 200 to 300. Might as well err on the side of caution and aim a little high @ 100. Then you'll still be in a 8" kill zone out to 300. I don't know how that will correlate to your reticle, but it should be close.

In theory, a BDC reticle can only work with one particular load (or loads with the same ballistics) under one density altitude. In practice, because nobody I know who has one shoots out past 400 yards, they will work well enough with a variety of loads. I'd recommend getting to a range when possible that allows you to shoot @ 100, 200 and 300 yards. Then stick with whatever load worked well.

saitotiktmdog, it is true that you could sight an M4 in @ 25 yards with M855 and be zeroed at 300 yards (again varying somewhat with density altitude). But that's something I'd consider inadequate for a hunting rifle or any long range shooting. It is good though for minimizing wind drift...as is any range 100 or under for most calibers. I could basically zero anywhere from 60-110 yards with my .308s and have no adjustment from my 100 yard zero. But it is good to get to a precise distance, then shoot out as far as you can to verify any calculations (or assumptions of any kind).
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 19:03
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Welcome to OT, Beers!

The correct answer to your question will depend on your bullet weight, ballistic coefficient (to a small degree but not so much at short distance), and muzzle velocity. 

For example, if you're shooting a typical 180 grain bullet with a BC of .400 - .500 and around 3000 fps muzzle velocity, a 200 yard zero would put you about 1.5" high at 100.

If you're shooting a 165 grain bullet with a BC in the same range and 3100 fps, you would be more like 1.25" high at 100 for a 200 yard zero.

200 grain bullet @ 2850... more like 1.75" @ 100 for a 200 yd zero.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 21:00
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With all the fancy reticles we have today most of the time it still comes down to Kentucky windage.I guess thats the reason black powder hunters back 100 years ago became so perficient with their iron sights,but they did practice alot!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/21/2010 at 22:28
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Thank you everybody. And RifleDude, that is the exact answer I was looking for. I shoot a 180gr at about 3000 fps. So taking your info I will sight in at 1.5 high at 100 yds.
 
The range I normally woudl go to does have a 300 yd range, but the guys I'm going with do not want to pay the $15 fee. Hopefully I will make it to that range sometime before we Elk season starts .
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/22/2010 at 08:09
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Originally posted by jonoMT jonoMT wrote:

Depending on the load, 1-2 inches high @ 100 is probably going to be about right. Without going into details, if you're staying at 300 yards or less, then you're going to have a drop of about 6" from 200 to 300. Might as well err on the side of caution and aim a little high @ 100. Then you'll still be in a 8" kill zone out to 300. I don't know how that will correlate to your reticle, but it should be close.

In theory, a BDC reticle can only work with one particular load (or loads with the same ballistics) under one density altitude. In practice, because nobody I know who has one shoots out past 400 yards, they will work well enough with a variety of loads. I'd recommend getting to a range when possible that allows you to shoot @ 100, 200 and 300 yards. Then stick with whatever load worked well.

saitotiktmdog, it is true that you could sight an M4 in @ 25 yards with M855 and be zeroed at 300 yards (again varying somewhat with density altitude). But that's something I'd consider inadequate for a hunting rifle or any long range shooting. It is good though for minimizing wind drift...as is any range 100 or under for most calibers. I could basically zero anywhere from 60-110 yards with my .308s and have no adjustment from my 100 yard zero. But it is good to get to a precise distance, then shoot out as far as you can to verify any calculations (or assumptions of any kind).
Yeah I agree it would not be the best for hunting. I thought I had completed my thought above but I was thinking that if you could determine the same realation for your particular rifle/scope combo, assuming that your groups at the larger ranges were acceptable, then theoretically you could aim for center of mass (kill zone) and always have a hit. Of course even communism works in theoryWink
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/25/2010 at 08:48
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Infidel, The obvious reply to your post is go to nikonhunting.com and click on the Spot On Ballistice Match Technology Program. This program lets you plug in all the known information you have, your scope (yes your scope) , make of ammo, bullet type and weight, MV. Hit fire and it will give you data for your BDC scope as well as a table of bullet drop, where you need to sight your rifle in at 100 yards on the target to be dead on at 200. It very user friendly and will provide you with a lot of useful information. Hope this helps I.?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: September/25/2010 at 09:40
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Wow, thats BMan! That was awesome
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/07/2010 at 03:26
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Edited by koshkin - October/07/2010 at 03:51
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