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If you're trying to use the iron sights, and you intend to use the rifle at any range beyond 25y, zeroinng at short range is only useful for getting on the paper so you can zero at 100 y/m more efficiently.
At 25y you can't get an accurate elevation. In addition, errors made at short range are magnified at longer range. A 1 inch error at 25 y is a 10 inch error at 250y. |
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Quoted:
If you're trying to use the iron sights, and you intend to use the rifle at any range beyond 25y, zeroinng at short range is only useful for getting on the paper so you can zero at 100 y/m more efficiently. At 25y you can't get an accurate elevation. In addition, errors made at short range are magnified at longer range. A 1 inch error at 25 y is a 10 inch error at 250y. For the sake of argument, say I am using a red dot optic. I understand 25/200 is the optimal, one setting, set it and forget it distance. I need a ballistic chart for that. |
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I zeroed my Kobra, mounted on an AK-74, for 300 yards. The problem is that I could not find a BC for the 7N6 bullet. I'm sure the BC is higher than the 55gr. M193 bullet, but it was all I had so I used it anyway. The calculator said it would come out to within +/- 5" out to 350 yards, and only need to hold over about a foot to hit at 400 yards. So far, it seems to be about right. No problem hitting steel silhouettes out to 430 yards. For 7.62x39mm, assuming 3.5" sight height over the bore, a 250 yard zero works pretty well as it will also put you within about 5" out to 250+ and you'll be 7" low at 300 yards. I'm just taking the 3.5" height over bore number from memory, I could be off. I think that's how high the Kobra sits, and I'm pretty sure most other Russian optics are close.
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My ballistic calc say to zero at 235 yards (or 4.56” high at 100 yards) to keep the bullet within +- 8” out to 294 yards.
7.62x39 has a trajectory like a rainbow when compared to 5.56 NATO, which is why it's very hard to ID 'the one true range' to zero at. The full chart is here: https://docs.google.com/Doc?docid=0AU9fZpC9S7gDZGNrOW5jaHNfODdkeGc4ZGJjYw&hl=en BSW |
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