Author Topic: Adjusting Front Post to Lower POI  (Read 3534 times)

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Offline rjinga

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Adjusting Front Post to Lower POI
« on: November 07, 2017, 05:24:12 PM »
Here are my Golden Tiger ammo targets at 25m and 100m (using the 100m position on the rear sight):



It's kind of hard to see, but there is a yellow + inside of each rectangle that marks the center point of the shot group. 

At 25m, I tried to touch the top of the front post to the bottom of the 2" red square.  The center point of the shot group was 0.997" above the bottom of the square.

At 100m, the top of the front post was in the position as shown in the photo (as best as I can recall).  The center point of that shot group was 3.812" above the top of the post (ignore the windage for now).

So, approximately how much would I need to move my front post up (counter-clockwise) to lower my POI at 100m by two or three inches?

Offline running-man

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Re: Adjusting Front Post to Lower POI
« Reply #1 on: November 07, 2017, 07:00:43 PM »
Here's the target I've always seen used for 7.62x39 (it's been around forever, you can find them preprinted on Amazon I believe).  The elevation lines, when printed on an 8.5"x11" standard sheet of paper are ~.35" apart, so it looks like 1/4 turn @ 25 meters gives you about 0.70" of travel if it's to be believed. 



Not sure about 100 meters, as I suspect it depends on where you zeroed your rifle. 


Assuming you are zeroing at 100m, I'd expect maybe ~2.8" per quarter turn based on the 0.70" @ 25m.  That's a huge WAG though. dntknw1

I always get wound around the axle when contemplating which way to move the front sight to get my POI in line with my POA.  Usually I just try one direction, then correct it twice as much the other way when I realize I went the wrong way!  chuckles1
Ask Blicero, there's always lots of trial and error and general awkwardness when it comes to me actually firing one of my SKSs (and trying to hit what I aim at).  I'm not ashamed to say that I'm much of a shot.   hunter)
Your postings give me inspiration though!  thumb1
      

Offline carls sks

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Re: Adjusting Front Post to Lower POI
« Reply #2 on: November 08, 2017, 08:40:03 AM »
good stuff R-man.  thumb1
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Offline Loose}{Cannon

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Re: Adjusting Front Post to Lower POI
« Reply #3 on: November 08, 2017, 08:00:14 PM »
Good reference RM!

OP....  you zero an sks with the rear sight on the battle zero setting and not on any of the numbered scales. The reason for this can be seen on the ballistics chart above.  If you zero the rifle on the battle zero at 25m, at that point the bullet it still traveling upward, and at 200m it comes back down to be on zero again. The purpose for this is to give you center mass out to about 250m and only having +/- a few inches above or below POA.  Of course, after zeroing at 25m on battle zero setting, you can also drop the leaf down to 100, 200, 300 etc and be on POA at that distance.

So...  If you zero at 25m on battle zero and leave it there, your POI will be roughly 3" high at 100 and 150, back on POA at 200, and about 5" low at 250, and about 14" low at 300.

Make sense?
      
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Offline Loose}{Cannon

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Re: Adjusting Front Post to Lower POI
« Reply #4 on: November 08, 2017, 08:22:15 PM »
What setting did you have the rear leaf on when you zeroed at 25m?
      
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Offline Loose}{Cannon

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Re: Adjusting Front Post to Lower POI
« Reply #5 on: November 08, 2017, 08:25:32 PM »
If you want your elevation scale on the leaf to match poi at respective distance, you should zero at 25m with the rear sight on battle zero.
      
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Offline Loose}{Cannon

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Re: Adjusting Front Post to Lower POI
« Reply #6 on: November 08, 2017, 08:48:12 PM »
For all I know... those 100m poi in your target is with the bullet coming back down, not on its way up which will make your entire leaf scale off and REALLY low out past 100 compared to where it should be.    ???
      
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Offline rjinga

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Re: Adjusting Front Post to Lower POI
« Reply #7 on: November 09, 2017, 08:31:03 PM »
OP....  you zero an sks with the rear sight on the battle zero setting and not on any of the numbered scales. The reason for this can be seen on the ballistics chart above.  If you zero the rifle on the battle zero at 25m, at that point the bullet it still traveling upward, and at 200m it comes back down to be on zero again. The purpose for this is to give you center mass out to about 250m and only having +/- a few inches above or below POA.  Of course, after zeroing at 25m on battle zero setting, you can also drop the leaf down to 100, 200, 300 etc and be on POA at that distance.

So...  If you zero at 25m on battle zero and leave it there, your POI will be roughly 3" high at 100 and 150, back on POA at 200, and about 5" low at 250, and about 14" low at 300.

Make sense?

After seeing the ballistics chart, yes it does.

What setting did you have the rear leaf on when you zeroed at 25m?

Based on a YouTube video that seemed to know what it was talking about, I had it set on the 100m setting.  Well, now I've got another reason to go back to the range.   :)