3x9 Duplex Reticle Calibration

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Mrlucky353
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3x9 Duplex Reticle Calibration

Post by Mrlucky353 »

I don’t ever expect to take a shot at an animal at 300 yards with a 7.62x39.
Bullet energy at that range approximates that of some 9mm pistols,
and precise shot placement could be elusive.

But steel plates are fair game.

The challenge was to quantify what is seen in the duplex reticle of my 3x9 scope
in order to help with hold over on shots well beyond zero range.

The target for today was an AR500 9”x12” plate, placed at 300 yards, and painted with a 6” orange bulls eye over a white background. I opted for the 3/8 inch thick steel plate because it makes a louder ‘ping’ than one quarter inch steel. However at 300 yards and with the wind at your back, you’ll see target movement more than you’ll hear the ping.

The 9x12 plate also provides some feedback for close misses of the 6” orange circle.
The 11 pound plate hangs from a simple garden shepherd’s hook (pic below).
Blank Target.jpg

My rifle is zeroed at 150 yards and prints 2 inches high at 100 yards.
But bullet drop at 300 yards is 25 inches.
At 9x magnification and 300 yards, the point of aim for a 25” drop is well into the thick black lower post and difficult to repeat consistently (pic below).
Reticle 25 inch drop 9x.jpg

So I decided to quantify the distance “D” (pic below) between the crosshair and the top of the thick bottom post at various distances and magnifications on my 3x9 scope to see if that would help with holdover.
Reticle D.jpg

The calibration process involved setting up a target with 1 inch squares (pic below) to visually verify ‘D’ at 50, 75, and 100 yards using different magnifications. That data was then linearly extrapolated for longer yardages. (Before going through all this trouble, I did several Google searches and turned up very little.
If this information is already out there, please don’t tell me!).
100 yard target with 1 inch squares.jpg

The data developed for the charts below can be useful when both the distance to your target
and the amount of your bullet drop are known. “Half-D” or mid-point hold overs or hold unders
for various distances and magnifications are also listed.
Chart 1 50 to 175 Yards.jpg
Chart B 200 to 300 yards.jpg


I knew from experimentation that bullet drop was roughly 25 inches at 300 yards.
Using the above data for 300 yards, I adjusted the magnification on my scope to 4.5x
so that the 24 inch “D” would closely match bullet drop.

I then used the top of the thick bottom reticle post (pic below) as my point of aim.
Reticle 300 yards 4.5 x.jpg

Add in normal amounts of wiggle and giggle, and holding right edge for a 3 knot crosswind component,
the pictures below show the result of today’s 3 shot group at 300 yards using the above technique.
3 shots in orange at 300.jpg
3 shots at 300 with ruler.jpg

Could I shoot this same 300 yard grouping again? Probably not.
But it was a fun ‘proof of concept’ exercise.

Ammo: Prvi Partizan 7.62x39 Round Nose
Rifle: CZ 527 Carbine
Scope: Bushnell 3x9 Extended Eye Relief


Steve
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Re: 3x9 Duplex Reticle Calibration

Post by mr surveyor »

that is some really good work. Really brings truth into the statement "Know your rifle". You got it down.
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Re: 3x9 Duplex Reticle Calibration

Post by akuser47 »

Great write up i love it and also never seen someone put this much into a 3x9 scope before i got infected by the tactical bug most my scopes were 3x9by40 still have 3 of them. Great work
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Re: 3x9 Duplex Reticle Calibration

Post by Ranch Dog »

Great write up Steve. I've done the same work at is part of the reason I have kept my scope choices simple. I only use two types of scopes; the Bushnell 1.5-4.5x32 for the standard installations on the Marlins, RGs, and the Zastava 85 and the Weaver K4 Classic Scout on the R92s and Ruger Mini-30.

My target berms have heavy bull panel with a 6" spacing on the wire that I use to hang the cardboard backed targets on. What I did is go to each target berm and paint the grid white starting at 100-yards out to 300 yards. Then, I sit at the bench with a notepad and start measuring the duplex against the grids. Here is the Banner's chart.
Crosshairs.jpg
My interest is the distance between the center of the crosshairs and the top of the duplex center post. My rifles are all sighted in at 100-yards but knowing the relationship of the distance between these two points and using that with the ballistic performance of the given cartridge to properly place shots has really paid off in performance out in the field.
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Re: 3x9 Duplex Reticle Calibration

Post by Mrlucky353 »

Thanks Guys.

The kind words are much appreciated.


Steve
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