Changing bcs to match velocity

338 dude

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I run multiple BC’s in my ballistic solver from Bryan Litz’s book ballistic performance of rifle bullets volume three and I have not had to change them in the two rifles I shoot long range with.
 

milo-2

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The standard has been to adjust your MV to 5-600 yards, get that to match, then true BC past those distances.
I just rebarreld my 6x47 Lapua shooting 110gr Sierra's. The last barrel, things never did match up and I ran 2 profiles for it in my Kestrel, one to 1K, and one past. After 1K, the bullet seemed to sprout wings, I needed to add 50fps and .012 more BC, even then it was like waking up to a dementia patient. Every day was a new day.
Like an above poster mentioned, list the bullet and someone may have some insight.
 

david g ranes

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To get my yardages and my clicks to come close I had to adjust my bc from 284 to 260 first time I’ve ever had to adjust like that wonder if that is a lot or not it’s 85.5 grain Berger in a 22 creedmoor and my clicks on my chart was way different than what the velocity said it should have been my velocity shows 3232 on two magneto speeds but my trued velocity shows 3187 David
 

338 dude

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To get my yardages and my clicks to come close I had to adjust my bc from 284 to 260 first time I’ve ever had to adjust like that wonder if that is a lot or not it’s 85.5 grain Berger in a 22 creedmoor and my clicks on my chart was way different than what the velocity said it should have been my velocity shows 3232 on two magneto speeds but my trued velocity shows 3187 David
My book does not list the 85.5 grain the only one ending in .5 is 80.5
image.jpg
 

milo-2

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To get my yardages and my clicks to come close I had to adjust my bc from 284 to 260 first time I’ve ever had to adjust like that wonder if that is a lot or not it’s 85.5 grain Berger in a 22 creedmoor and my clicks on my chart was way different than what the velocity said it should have been my velocity shows 3232 on two magneto speeds but my trued velocity shows 3187 David
What were the conditions? You really need a low wind day to true dopes, especially with a light bullet like that, even with the uber high speeds.
 

milo-2

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May 1, 2011
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Location
Gillette, Wy
To get my yardages and my clicks to come close I had to adjust my bc from 284 to 260 first time I’ve ever had to adjust like that wonder if that is a lot or not it’s 85.5 grain Berger in a 22 creedmoor and my clicks on my chart was way different than what the velocity said it should have been my velocity shows 3232 on two magneto speeds but my trued velocity shows 3187 David
Also, not sure how far you are shooting these drops, but because you are above 3000 fps, your BC input should be higher, not lower. Are the distances verified?
 

david g ranes

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Yes the yardage was verified with 2 range finders a g7 br and a sig 3000 no wind no mirage 690 yards using geo BallisticsARC ballistic program joe there told me my atmospherics were off due to putting them in off a weather app but I’ve used the same procedure for years using gunwerks ballistic app and every thing worked great since they keep saying they are building a new app for a year I used geos app for my 6 mm Remington it worked fine just having trouble with the 22. David
 

david g ranes

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Simple question not so simple answers I know the bcs I know the conditions and yardage just would like to know the most people have changed bcs to match their drops David
 

73driver

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Aug 24, 2011
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I just trued up my Silhouette Match rifle. I had chronographed MV and the bullet BC and was trying to adjust them to match my drops. I worked out the dial ups that worked for the 4 silhouette yardages plus one dial up required for 500 yards. I could never quite jigger MV and BC in my app to match what was working. I just started over and used the 547 yards, the chronographed MV, the listed BC and put in the dial up required and had my Strelok Pro adjusted the value per click. The Strelok app came up with .228 moa per click and when I tested it against the dial ups that worked the new moa value per click was dead on for 5 different yardages. Maybe you need to true up your scope click values?
 

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