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PostPosted: November 10th, 2014, 4:38 pm 
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Harlequin Duck
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So, we sighted in our rifles/scopes Saturday, and just did some fun target shooting. (Having fun more than anything.)
We even had a .22 cricket for the 2 younguns, and they had a BALL!!!!
We shot several different rifles, .223, .243, .270, .300 win mag, and an AR chambered in 7.62x39. (Each rifle has a scope.)

Here is my observation from Saturday (which also comes with a question)...
When we sighted the rifles in (dead zero) at 50 yards, they were about 6" (average) high at 100 yards
Or, if the rifle was already sighted in (dead zero) at 100 yards, they were about 8" (average) low at 50 yards

This was the case with EVERY rifle we had, except the AR (which was even greater). We are going to set up targets again, and "re-test" this.
Anyone else ever had any experience like this?
The only explanation we could come up with is the fact that the scope sits higher on top of the gun.
What say ye???

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PostPosted: November 10th, 2014, 6:16 pm 
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Gadwall
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A bullet travels on an arc. My 300 mag is on 2-3" high at 100 and dead on at 200, about 8 low at 300 400 is close to 20" low


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PostPosted: November 10th, 2014, 10:21 pm 
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Tundra Swan
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Hey MusicMan,
Here's a link for the Winchester Ballistics Calculator.
Most of the "brand name" ammo companies have one available also.
You simply select your cartridge, sight distance, scope height, & few other variables ... then enjoy.
Good Luck this season.

http://www.winchester.com/learning-cent ... light.aspx

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PostPosted: November 10th, 2014, 10:52 pm 
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Canvasback
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Rifles sighted in at further distance will hit low at close since the scope axis is higher than the bore axis. 6 inches sounds like a bit much. I usually notice 1 inch or so.


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PostPosted: November 11th, 2014, 9:25 am 
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Harlequin Duck
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Ifid wrote:
A bullet travels on an arc. My 300 mag is on 2-3" high at 100 and dead on at 200, about 8 low at 300 400 is close to 20" low


From what I have studied, your bullet is actually not arcing. It is flat at 100 and drops 2-3" at 200 (which is normal)

I just could not believe the difference we were seeing (consistently) at 50 and 100 yards.

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How many are your works, LORD! In wisdom you made them all; the earth is full of your creatures. Psalm 104:24
I will sing to the LORD all my life; I will sing praise to my God as long as I live. Psalm 104:33


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PostPosted: November 11th, 2014, 10:28 am 
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Tundra Swan
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Some already hit on this but look closely at the ballistic tables and if you don't have one that already allows you to add your scope and bore offset then keep looking. There are some smart phone apps out there that do a good job.
A dead zero sight in at 50 is going to yield some very unpredictable results out at 100 and beyond.

In any case if you are wanting to get your 100 150 and 200 to a more realistic target strike then you MUST adjust your short distance target to correspond with the ballistics table.
Problem is that it is going to be in the .01 inch increments is you try to use an arbitrary distance like 50 yards.

I think what you are trying to accomplish is what is commonly referred to as "Battle Sight Zero."
There is a short yardage where the bullet crosses zero (in the way up) that corresponds to another zero crossing down range (on the way down).
for the 5.56 in the AR is was 25m and 250m therefore you could "battle sight zero" at 25 and be dead on at 250.
The 300 mag is something close to that (which is why I use it) but not exactly the same.

But, those other calibers you mentioned are nowhere close to that. You will need to determine the "Battle Sight Zero" for each caliber individually and then zero "at that distance" If it happens to be 29 yards for one caliber for example, sighting in at 50 yard will cause a huge error down range.

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PostPosted: November 11th, 2014, 1:19 pm 
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Tundra Swan
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ok... let me explain this visually and it will make all the sense in the world.. but i do want to clear something up from the get go A BULLET DOES NOT RISE COMING OUT OF THE GUN!!!! physics doesn't allow that one to happen... yes the bullet begins to arc as soon as it leaves the barrel due to gravity but it never rises!!!

in the first diagram.. this would be if a shooter was shooting a gun with a scope.. the scope perfectly level with the world as well as the gun barrel perfectly level with the world... the bullet and the line of sight would never interesect because gravity is causing the bullet to drop and due to the offset of the scope (height) and the barrel these two obects can not cross no matter what.

Image

the second diagram shows what is truely going on and where the misconception of a "bullet rises" out of the barrel comes from...

Image

as you see when you adjust your line of sight (zeroing in a scope at x distance) you are actucally adjusting your line of sight in minute measurements to get your line of sight and the bullet trajectory to cross.. now depending your guns ballistic trajectory and where you zero it in (say 50 yards) it could be high at 100 yards as the image dictates. BTW those ore the exact same arcs one is just rotated. obviously the gun angle and line of sight are overly exaggerated to show whats going on. now it makes sense visually huh??

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Last edited by deeksdown on November 11th, 2014, 1:31 pm, edited 1 time in total.

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PostPosted: November 11th, 2014, 1:27 pm 
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Harlequin Duck
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Makes perfect sense deeks
This is what we were discussing saturday. That the barrel HAS to be "angled" upward to achieve a 100 yard zero with a scope. It just makes sense (by laws of physics).

However, we were thinking it would be off by like .5-1.5" at 50 vs 100 yards. Not 6-8"!
That's what surprised us.

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I will sing to the LORD all my life; I will sing praise to my God as long as I live. Psalm 104:33


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PostPosted: November 11th, 2014, 1:51 pm 
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Pintail
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What type scope rings/mounts did the rifles have? The higher the scope sits from the bore, the greater the difference in Line of Sight vs POI. This is very common with AR type guns since they typically have a higher mounted scope.

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PostPosted: November 11th, 2014, 3:08 pm 
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Harlequin Duck
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HippieKiller wrote:
What type scope rings/mounts did the rifles have? The higher the scope sits from the bore, the greater the difference in Line of Sight vs POI. This is very common with AR type guns since they typically have a higher mounted scope.


They are all a little different.
Some are 1.5"
2"
And the AR is 3"

After we shoot again, I will post all results with photos.
Thanks for all the input.

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How many are your works, LORD! In wisdom you made them all; the earth is full of your creatures. Psalm 104:24
I will sing to the LORD all my life; I will sing praise to my God as long as I live. Psalm 104:33


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PostPosted: November 11th, 2014, 5:52 pm 
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Pintail
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music_man wrote:
They are all a little different.
Some are 1.5"
2"
And the AR is 3"


I'll bet you find less fluctuation on the lower scopes. Once you start getting out to distance, that 1"-2" is inconsequential. At close range, it will really show up though. Looking forward to seeing your follow up pics/results!

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PostPosted: November 13th, 2014, 11:18 pm 
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Redhead
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deeksdown wrote:
ok... let me explain this visually and it will make all the sense in the world.. but i do want to clear something up from the get go A BULLET DOES NOT RISE COMING OUT OF THE GUN!!!! physics doesn't allow that one to happen... yes the bullet begins to arc as soon as it leaves the barrel due to gravity but it never rises!!!

in the first diagram.. this would be if a shooter was shooting a gun with a scope.. the scope perfectly level with the world as well as the gun barrel perfectly level with the world... the bullet and the line of sight would never interesect because gravity is causing the bullet to drop and due to the offset of the scope (height) and the barrel these two obects can not cross no matter what.

Image

the second diagram shows what is truely going on and where the misconception of a "bullet rises" out of the barrel comes from...

Image

as you see when you adjust your line of sight (zeroing in a scope at x distance) you are actucally adjusting your line of sight in minute measurements to get your line of sight and the bullet trajectory to cross.. now depending your guns ballistic trajectory and where you zero it in (say 50 yards) it could be high at 100 yards as the image dictates. BTW those ore the exact same arcs one is just rotated. obviously the gun angle and line of sight are overly exaggerated to show whats going on. now it makes sense visually huh??


You would be amazed at how hard this is to explain to folks. I was told by my drill sergeant in basic training I was an idiot when I explained to her that bullets can't rise, they are just aimed up to arc. You can't argue physics with a drill sergeant... You just end up doing more push-ups.

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PostPosted: November 14th, 2014, 4:30 pm 
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Harlequin Duck
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I've always wondered why everyone thinks a bullet rises. As someone that doesn't deer hunt much, I have not shot a rifle as much as some. So, when people (deer hunters) told me a bullet rises after leaving the barrel, I just never argued with them. However, it always puzzled me how that was possible.

I'm hoping to shoot again tomorrow, results to follow....

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How many are your works, LORD! In wisdom you made them all; the earth is full of your creatures. Psalm 104:24
I will sing to the LORD all my life; I will sing praise to my God as long as I live. Psalm 104:33


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PostPosted: November 27th, 2014, 9:48 am 
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Pintail
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Did you ever do any follow up shooting?

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PostPosted: November 28th, 2014, 12:02 am 
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Harlequin Duck
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HippieKiller wrote:
Did you ever do any follow up shooting?


Not yet
The day we planned to go, my buddy got sick.
In the mean time we had our first baby (a boy), so shooting, hunting, etc. Has taken a major step down the importance list. But, we are still planning to shoot as soon as everything calms down a little.

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How many are your works, LORD! In wisdom you made them all; the earth is full of your creatures. Psalm 104:24
I will sing to the LORD all my life; I will sing praise to my God as long as I live. Psalm 104:33


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PostPosted: November 28th, 2014, 10:52 am 
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Pintail
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Congrats on the kiddo! Those little boogers are a blast.

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PostPosted: November 28th, 2014, 9:49 pm 
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Harlequin Duck
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HippieKiller wrote:
Congrats on the kiddo! Those little boogers are a blast.


Thanks man!

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How many are your works, LORD! In wisdom you made them all; the earth is full of your creatures. Psalm 104:24
I will sing to the LORD all my life; I will sing praise to my God as long as I live. Psalm 104:33


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