Bullet coeff

[eddiesindian]

How many of you guys have used used the manufactures stated ballistic coefficiency numbers wether it be G1 to G8 as drag functions and found them to be spot on.

[wbm]

I use manufacturers published BC but don't know if I have ever found one "spot on". For the most part, variations in velocity, altitude, temperature, etc. have been somewhat more "predictive" of performance of a bullet at distance than "correctness" their listed BC. Sierra is one of the few that use variations in BC relative to velocity in their published data....here is an example.

https://www.sierrabullets.com/store/product.cfm/sn/1715/264-dia-65mm-107-gr-HPBT-MatchKing

[eddiesindian]

For me, Ive found berger,s ballistic coeff along with there calculators to be more on target. If I could afford Bergers for all my calibers?.....Id go Berger.

[eddiesindian]

I use manufacturers published BC but don't know if I have ever found one "spot on". For the most part, variations in velocity, altitude, temperature, etc. have been somewhat more "predictive" of performance of a bullet at distance than "correctness" their listed BC. Sierra is one of the few that use variations in BC relative to velocity in their published data....here is an example.

https://www.sierrabullets.com/store/product.cfm/sn/1715/264-dia-65mm-107-gr-HPBT-MatchKing
Glad you refreshed my memory
I remember seeing this. I looked it up while using there 150gr smk,s on my HS. I dialed up .417 due to my pill going 2815 for that particular load.
Have you personally used there there ball. coeff #s judged by the speeds of your pill and found them to be at least close if not spot on?

[stomp442]

Bryan Litz has a couple books out where he has tested a lot of other manufactures bullets using the same method that he does for all of Bergers Bullets and he provides G7 values as well as averaged G1 values. I have found his numbers to be as close to spot on as one can get. Published BC's especially those by Nosler are way over inflatted. Most of the time Sierra is pretty darn close if you average the velocity band BC's to what Mr. Litz is getting. Hornady has gotten a lot better with their newer line of bullets with dopler testing and also provides G7 values for those as well. Nosler only tests at short range and at very high velocities which produces the highest numbers possible for advertising purposes. I have found as a general rule to take about 10% off of what Nosler publishes for a corrected BC to plug into my shooting solution and that gets me pretty close.

[eddiesindian]

Agreed stomp. hornady bc #s for me have not agreed with my out come.

[LoneWolf]

A lot plays the BC. I've G7 to be the most accurate for BTHP Match type bullets. I start with the manufacturer BC, get my velocity from a chrono. Then true my DOPE with actual drop data and adjust my velocity in my calculator.

One of the factors will most likely have to change in order to true your drop data. the easiest to adjust is velocity as 99% of people don't have the equipment or mathematic ability to recalculate the BC. If you're using G1 then you need to calculate the trajectory at multiple distances as the G1 function changes as velocity falls off.

I have not read Litz's books, but this is my basic understanding from self tests since I shoot at multiple locations ranging from 400ft above sea level to 5,000ft above sea level. Once I have true my data making atmospheric adjustments is pretty simple and for the most part spot on within 1000yds.

[LongRange]

i do the same thing as LW...G1 is always way off unless entering multiple velocities and then still needs to be adjusted...G7 is always very close and then once you adjust your velocities to match your actual drops your set and using the G7 BCs its much easier to true up.

[wbm]

Have you personally used there there ball. coeff #s judged by the speeds of your pill and found them to be at least close if not spot on?
Yes. Quite a bit actually. I live at 7000 feet so obviously the performance of a given bullet is going to be enhanced. Last week I loaded the 107gr Sierra in 6.5mm to 3000fps and shot it to be dead on at 100. Then I moved to 300, 400, and 500. After measuring the drop at longer distances I plugged the data into JBM. After including bullet weight, velocity, BC, elevation, temperature, humidity even, the predicted results came out pretty close to "real life" results. But "spot on"?...Don't know but close enough.

[LoneWolf]

500yds is not far enough to tell in my experience. You need to go to at least 800-900yds or better if you can.

[wbm]

I can't see that far. :cool:

[eddiesindian]

A lot plays the BC. I've G7 to be the most accurate for BTHP Match type bullets. I start with the manufacturer BC, get my velocity from a chrono. Then true my DOPE with actual drop data and adjust my velocity in my calculator.

One of the factors will most likely have to change in order to true your drop data. the easiest to adjust is velocity as 99% of people don't have the equipment or mathematic ability to recalculate the BC. If you're using G1 then you need to calculate the trajectory at multiple distances as the G1 function changes as velocity falls off.

I have not read Litz's books, but this is my basic understanding from self tests since I shoot at multiple locations ranging from 400ft above sea level to 5,000ft above sea level. Once I have true my data making atmospheric adjustments is pretty simple and for the most part spot on within 1000yds.
that's pretty close to what ive done.
Ive done my own math and have come up with a formula that's worked for me for years providing I have correct amount of drop at any given distance.

[eddiesindian]

500yds is not far enough to tell in my experience. You need to go to at least 800-900yds or better if you can.
Agreed. from what I've noticed is that if I'm running my pills 2500-2600 which is what I usually run when shooting 400-800 yard matches, the BC numbers come into play at 600 ish. When I use my other rigs to go out to 1K, the BC numbers really come into play from 8 out past 1k due to the increased speeds 2800-2850ish.

[eddiesindian]

Ive had trouble agreeing with Hornady 68gr HPBT in .224 BC numbers. Its a secant ogive which for me is odd that they show the BC numbers in a G1 and not G7. Ive converted to G7 and ran the numbers but my actual drop doesn't match. I gave in and just adjusted my come ups old school. Its the only pill Ive had trouble with. Ive researched via the world wide net and found others to have the same issues and they,ve come up with there own BC numbers.

[LoneWolf]

For me Hornady bullets were inconsistent anyways. I won a couple matches with the 105AMAX, but when they get squirrely it gets ugly quick lol.

[Rob01]

Never found Hornady bullets inconsistent but never shot the 105 AMAX. I have shot the 6mm 105 BTHP and match bullets in 6.5mm and .30 and they all shot very good and the BCs were on. I won, top 5 and top 10 a lot of matches with Hornady bullets since 2004. I run all my data a head of time and bring it to the match and using JBM I have never been off more than .2 mils at 1000, which is about 7",and mostly on or maybe .1mil but that can also be small shifts in environmental conditions. I have shot them farther as well in matches. Out to 1350 yards and they did what they should have. With their new Doppler radar numbers the BCs will hold much more true in the future.

[LoneWolf]

Try shooting Bergers or Sierras. I went from being in the top 5 regularly to the top 3. .2Mils makes a difference in the wind. That's missing by a tenth or catching the edge of the target on a close wind call!

[No.343]

I shot my first 600 yard f-class match with 6mm Hornady 105 Bthp recently. I used the published data for come ups, since I didn't practice before hand and my first sighter was a 10.

[eddiesindian]

Try shooting Bergers or Sierras. I went from being in the top 5 regularly to the top 3. .2Mils makes a difference in the wind. That's missing by a tenth or catching the edge of the target on a close wind call!

I do use them. If I could afford it, I would use Bergers for all my calibers.... Be as it may, its only 4 different calibers but it adds up.

[Rob01]

Try shooting Bergers or Sierras. I went from being in the top 5 regularly to the top 3. .2Mils makes a difference in the wind. That's missing by a tenth or catching the edge of the target on a close wind call!

Have shot both. No difference in placing.

I was talking elevation of .2 mils. .2 mils of wind is about 1mph and if you can dope the wind to 1 mph at 1000 yards with no flags then you are **** good. Not many can.