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scope height in relation to bore

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grimreaper21 View Drop Down
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    Posted: November/11/2010 at 12:10
I'm wondering what effects my scope will have based on what height I mount it above the bore? Just read an ammo box and it listed its trajectory statistics then stated specs with scope at 1.5'' above bore.  I'm looking at rings that will be mounted at 1.2'' centerline. I assumed I'd be better off mounting it as low as possibly allowed, but now i'm not so positive.  There are also options for 1.6'' centerline.. etc. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SD Dog Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 12:44
Lower is generally better.  What is listed on the box gives a reference point.
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grimreaper21 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote grimreaper21 Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 13:01
will it change trajectory any, or be easier/harder to sight zero, or require more turret clicks in one direction ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonoMT Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 13:15
The lower it is mounted, the more likely you will be able to get a decent cheek weld. That will give you a more consistent sight picture, which will lead to more repeatable results. I have not seen a significant change in trajectory by switching less than 1/2" in scope height. As for requiring more turret clicks, generally no, unless you were to somehow switch from rings that have built in elevation to ones that don't. Usually it's the base (typically 0MOA, 20MOA or 40MOA) that will determine whether you need fewer clicks in elevation.
Reaction time is a factor...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SD Dog Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 13:31
Lower the scope is mounted the closer to the bore of the barrel it is.  I know, a duh statement.  There is noo real improvement on ease of zeroing nor will it require more clicks.  The big advantage is what JonoMT stated, it will make it easier to get a good, repeatable check weld.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dogger Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 13:46
Borrowed this from another forum, will post the entire thread, interesting discussion on this topic:
 
"Don't want to beat a dead horse, but I guess it depends upon what your definition of "flat shooting" rifle is. Isn't the definition of a flat shooting load where it hits the target at various ranges??? Let's try it this way. Which of the following loads is the "flatter shooting load?"

A. Dead on at 200, 7.5" low at 300; 23" low at 400
vs.
B. Dead on at 200, 6.75" low at 300; 21" low at 400

I think we would all say that load B is the flatter shooting load. Agree??

Guess what? The two loads are identical: same bc .287, same mv 3000 fps, same everything, EXCEPT height above bore. The "flatter shooting" load is the one with the scope 3.5" above bore, not the one that was 1.5" above bore.

Again trajectory relative to the direction of the bore is not affected by bore height; however, tradjectory relative to the horizon is affected by bore height."
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Dogger View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dogger Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 14:03
Sorry, that link is no good, this one should take you to the thread:
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Poodleshooter1 Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 16:26
Yes, a higher bore gives the illusion of less drop at extended ranges. The opportunity cost of a higher mount is that it makes extremely close range shots on tiny targets more difficult.
For a long range rig, higher is great. It's also fine for a purely big game rifle.
For a rifle that needs to hit small 1" targets at 5yds-100yds, a low mount is a better idea.
For a rifle that needs to hit small 1" targets past 75yds, a high mount is fine.
For some rifles with high stocks relative to the bore, such as most ARs, a high mount may be the only way to get a good cheek weld.
In short, don't put extra high rings on your squirrel rifle. 

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Rich Coyle View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rich Coyle Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 20:27

                                          FASTEST IS NOT ALWAYS FLATTEST

                                                                           and

                                              Shooting an unmodified Savage .223

 

                                                      

                                                           January 9, 1996

 
Does the height of the rings above the barrel affect trajectory?  Sixty shots says, “Yes!” Arbitrarily I decided on a single ten shot group at 100, 200, and 300 yards with two scope heights.  According to the computer, if you sight in a firearm at, say, two hundred yards with the low or the high sight, it hits dead on at two hundred yards.  Novel concept.  The fun information is at one hundred yards or three hundred yards.  And beyond.
 
I used a Savage .223 with the 26" blued (not stainless) barrel for the test.  A trigger job by Bud Hopson (Lock, Stock, and Barrel, 115 S.W. "H" st., Grants Pass, Ore. 97526 (541) 474-0775) brought the pull down to about two pounds.  Th scope was 8X - 32X Burris target scope.
 
The loads consisted of a 65 grain JLK bullet (.397 sea level ballistic coefficient corrected to .411 for 1100 feet at the Grants Pass range according to the computer), a neck sized, trimmed to length Remington case with a deburred and squared flash hole holding a CCI BR-4 primer.  The powder charge was 27 ½ grains of VarGet. The cases had a weight tolerance of .2 grains and have been fired four times.  The average velocity for the first thirty was 3221 feet per second with a standard deviation of twenty-one.  (Who knows what standard deviation is, anyway?  It shows up on the screen, so we read it.  I think it's kinda like a group.  If it's big, we don’t mention it.)
 

                                   The HIGH rings: scope 2.2 inches above the bore.

 
The temperature started at forty-two degrees and went up to forty-eight degrees during the four hour session.  All shooting was done at 32X.  The targets were five eights inch squares.
 
The Burris settled on the left two hundred yard target to start.  The first five shots appeared to make a group that looked more like a one hundred yard group in the square.  I admired the group awhile through the scope.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tohunch Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 22:18
I'm not an expert. But I knew that scope height has no relation to trajectory. The trajectory stays the same if the scope is mounted 1" off the barrel, 6" off the barrel or no scope at all.

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grimreaper21 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote grimreaper21 Quote  Post ReplyReply Direct Link To This Post Posted: November/11/2010 at 23:45
Excellent great find, wasn't expecting it to make THAT much of a tangible difference.  learn more and more every day.  thanks again.
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Rich Coyle View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rich Coyle Quote  Post ReplyReply Direct Link To This Post Posted: November/12/2010 at 06:37
tohunch,
 
Read the last sentense again.  Look for the word "APPARENT".  If you haven't tried what I did or ran the "test" with a computer ballistic, you probably shouldn't comment.
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