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Post by ozark on Feb 4, 2010 21:05:26 GMT -5
A summary on this thread is probably not needed but I want to list some numbers on my favorite deer rifle. .243 Winchester. I am listing data for the 100 grain bullet: Zero it in 2.5" High at 100. This will be 3" high at 140 yds. That is mid range trajectory and the highest point above line of sight the bullet will get. Note that it gained .5 inches between 100 and 140. Now it begins to slowly drop to reach 200 yards 1.9 inches high. This gives me a 283yard Maximum point blank range. On a deer I can aim dead on from muzzle to 283 yards without the bullet wandering out of the kill zone. That for the hunter is a confidence builder. It also shows why the .243 Winchester cartridge is popular. BC of 351.
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Post by rogerdailey on Feb 10, 2010 10:05:21 GMT -5
Has anyone seen a MPBR calculator that considers group size? The one I've used calculates MPBR based on ballistics and target size only.
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Post by deadeye on Feb 11, 2010 20:16:55 GMT -5
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Post by whelenman on Feb 12, 2010 8:04:27 GMT -5
You should be able to just subtract the average amount your groupings deviate from point of aim at the initial point blank range computed from the size of the kill zone and get in the ballpark. Of course groups in the field aren't groups from the bench so there's a lot of leeway regardless. Unless you can recreate exactly the situation you'll be shooting from in the field you can't get a true picture and if you could just check on the targets if you think you can stay inside a circle of the desired radius. That's the method I use when sighting in hunting rifles. I shoot circles at range and see if I can stay inside the radius with all shots. I have a friend who swears by small balloons at varying ranges for hunting practice.
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Post by rogerdailey on Feb 12, 2010 9:37:45 GMT -5
deadeye - I have seen one's that allow setting of a vital zone size, but I believe they all assume a 0.0" group size. In other words; the actual vital zone size would increase by my group size at the calculated MBPR.
whelenman - very good point about field group size vs. bench group size. I use "bench rest" type techniques for load development, but I use "field" shooting techniques for zeroing. I try to duplicate the form I expect to use in the field. For example, when zeroing, I don't rest the forearm on the bench rest - I hold the forearm in hand and rest my hand on the bench rest.
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