TNW Aero carbine, 16" barrel, 10mm caliber.
I bought one of these 10mm carbines and like the way it handles and functions. I have a question about ballistics from the 16" barrel. I have a red dot mounted on the receiver and had it shooting to zero at 25 yards. I took it over to the 50 yard range and was surprised to see that it was shooting about 12 inches high and about 6 inches right. If I held my dot 12 inches below the center of the target and 6 inches to the left, they dropped right into the center rings. My initial thoughts were that if I am zeroed at 25 yards, I would be a little low at 50 yards but instead i'm way high?? Would I be better off zeroing the carbine at 50 yards and compensating at the 25 yard targets? I'm using 180 grain bullets. Thanks for any advice or information!
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Remember that your bore and your optics do not share the same plane. In order for them to intersect at some point, they have to angle towards each other. In your case, to be zeroed at 25 yards, the scope is aimed "downwards" a fair angle to make that intersect happen at that distance. As a result, the projectile will still be rising. My guess is it will still be rising out to probably just under 100 yards just guessing on the height above the bore the optic is mounted and the ballistic of the 180 grain 10mm (which can vary wildly depending on whether it is a true 10mm load, or a lite load). After that, it will then start falling in its parabolic arc.
A lot of hunters use "point blank zero". Rather than reinvent the wheel, I just found a site real quick with some illustrations that better explain than I likely could. The first graphic is what I was describing above and at the bottom of the page it talks about point blank zero.
https://www.everydaymarksman.co/marksmanship/point-blank-zero/
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Thanks for the info! Makes sense! I am going to check out the link you sent.
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"Remember that your bore and your optics do not share the same plane."
^^^CORRECT^^^
When boresiting an AR type firearm @ 25 yards, I adjust the crosshairs/dot about the same distance above the laser dot as the optic is above the boreline. This is the starting point. You need to decide where it's best to have the actual 'zero'.
For something like the 10mm, maybe it can work with a 100 yard zero. A 9mm might be happier with a 50 yard zero.
The 'up close' offset really isn't an issue unless you're shooting rabbits. My AR9 PDW dot optic is dead on @ 50 yards and hits at the bottom of the 4-6(?) MOA dot @ 100 yards. This provides assurance that out to 100 yards, all hits will be within the coverage of the dot.
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