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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
my drop chart doesn`t match at 500yds and beyond?
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<blockquote data-quote="Brent" data-source="post: 20806" data-attributes="member: 99"><p>Thanks for the time and help everyone. I`ll try to fill in the blanks and clarify some choppy statements, tried to be brief, sorry for the confussion.</p><p></p><p>Temp +69 deg F</p><p>Alt. approx. 150' above sea</p><p>horizontal</p><p>wind 10-20 at 11 o`clock (12 being muzzle end)</p><p>1 in 14 twist</p><p></p><p>I`m useing two different Crony brand cronys at 15', and both read between 2525 and 2610 with variances as much as that between them on the same shot. And top of that one will be faster one time and the other the next.</p><p> I think these are ball-park brand cronys, wish I had bought a good Oehler model.</p><p></p><p>Bullets print perfect holes at all ranges in paper and plywood backer with no evidence of elongation and if I remember correctly the programs indicatd quite a slow twist rate of between 19 and 21 depending on muzzle vel.</p><p></p><p>The first moa chart is exactly the mark set at on the leopold dial that my bullets hit dead center for each distance indicated. The second chart below that is the exact moa the two programs I use come up with, based on 2550 fps with a .546 BC.</p><p></p><p>But the main reason I used this chart at this vel. and BC is not just that my crony said 2550 but I feel more importantly that the moa adjustments for the first 400yds matched exactly those of mine.</p><p></p><p>I was unable to duplicate this 400yd path with any manipulation to MV or BC. It seems no mater what I do to MV or BC or combination of both on the program, if it matches perfectly to 400yds it is always flatter at 500 and beyond than my groups print.</p><p></p><p>What I ment to say on the 800yd group was, when I shot my 800yd groups dialed in at the 31.75 I suspected I needed the group printed 15" low and 10" group. So on the program if I entered in 2400 MV thinking my crony is lying to me, I find that would be more like it. </p><p></p><p>Only one problem, that chart indicates my bullet should not be flying as flat as it apparently is by far at up to 400yds if it were going that slow. It would be printing several inches lower at my setting of 2.25, 5.25 and 9.00.</p><p></p><p>The main reason I try to find a drop chart on the program matched to my known drops to 400yds is just to establish a path my bullet is following for the further distances to keep them on the paper.</p><p></p><p>One more observation I`ve made correctly I hope is that if my scope is not calibrated for true moa and just 1" at 100yds instead, I would indeed be needing more clicks at the greater distances to make up for this especially if it is slightly under an inch.</p><p></p><p>What is the most exact way to measure this in your experiance?</p><p></p><p>I checked out the chart with a BC .450 and it seemed to be real close at 700yds but seems 800yds is SEVERAL inches off still.</p><p>I`ll go to the range again and check a few things out. I was going to go back to 900 and 1000yds but looks like my scope has about 34.75 moa maxed out with a .025" shim already under the rear base.</p><p></p><p>I wonder if like you say Warren, the bullet might be "overspun" and BC is falling off at distance as a result. What you say Darryl about matching the program to the product hit the nail right on the head. Thanks again for the quick response with all the help and suggestions.</p></blockquote><p></p>
[QUOTE="Brent, post: 20806, member: 99"] Thanks for the time and help everyone. I`ll try to fill in the blanks and clarify some choppy statements, tried to be brief, sorry for the confussion. Temp +69 deg F Alt. approx. 150' above sea horizontal wind 10-20 at 11 o`clock (12 being muzzle end) 1 in 14 twist I`m useing two different Crony brand cronys at 15', and both read between 2525 and 2610 with variances as much as that between them on the same shot. And top of that one will be faster one time and the other the next. I think these are ball-park brand cronys, wish I had bought a good Oehler model. Bullets print perfect holes at all ranges in paper and plywood backer with no evidence of elongation and if I remember correctly the programs indicatd quite a slow twist rate of between 19 and 21 depending on muzzle vel. The first moa chart is exactly the mark set at on the leopold dial that my bullets hit dead center for each distance indicated. The second chart below that is the exact moa the two programs I use come up with, based on 2550 fps with a .546 BC. But the main reason I used this chart at this vel. and BC is not just that my crony said 2550 but I feel more importantly that the moa adjustments for the first 400yds matched exactly those of mine. I was unable to duplicate this 400yd path with any manipulation to MV or BC. It seems no mater what I do to MV or BC or combination of both on the program, if it matches perfectly to 400yds it is always flatter at 500 and beyond than my groups print. What I ment to say on the 800yd group was, when I shot my 800yd groups dialed in at the 31.75 I suspected I needed the group printed 15" low and 10" group. So on the program if I entered in 2400 MV thinking my crony is lying to me, I find that would be more like it. Only one problem, that chart indicates my bullet should not be flying as flat as it apparently is by far at up to 400yds if it were going that slow. It would be printing several inches lower at my setting of 2.25, 5.25 and 9.00. The main reason I try to find a drop chart on the program matched to my known drops to 400yds is just to establish a path my bullet is following for the further distances to keep them on the paper. One more observation I`ve made correctly I hope is that if my scope is not calibrated for true moa and just 1" at 100yds instead, I would indeed be needing more clicks at the greater distances to make up for this especially if it is slightly under an inch. What is the most exact way to measure this in your experiance? I checked out the chart with a BC .450 and it seemed to be real close at 700yds but seems 800yds is SEVERAL inches off still. I`ll go to the range again and check a few things out. I was going to go back to 900 and 1000yds but looks like my scope has about 34.75 moa maxed out with a .025" shim already under the rear base. I wonder if like you say Warren, the bullet might be "overspun" and BC is falling off at distance as a result. What you say Darryl about matching the program to the product hit the nail right on the head. Thanks again for the quick response with all the help and suggestions. [/QUOTE]
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my drop chart doesn`t match at 500yds and beyond?
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