'BC' again

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Dcoy
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'BC' again

Post by Dcoy »

For long range guys,maybe 'BC' stands for 'be careful'.I say that after reading a very interesting article in the latest issue of VHM.The article titled,'Inaccurate Specifications Of Ballistic Coefficients' is eye opening to say the least.Worth reading by everyone but certainly long range shooters.The authors tested the 'BCs'claimed by 5 bullet manufacturers and state:

"Results in the table show that manufacturer claims regarding bullet BC often are exaggerated.This exaggeration leads to inaccurate predictions of bullet drop,wind drift and impact energy."

The example they give to explain their charts reads:

"An example demonstrates the implications of an inaccurate BC for the Berger 115 grain VLD shot at 3148 fps.For a zero range of 200 yds and a 10mph crosswind,using the BC of 0.523 gives a drop of 45.1 inches,a wind drift of 19.6 inches,and an impact energy of 1,180 ft-lbs at 550 yds for atmospheric conditions of 30 degrees F,zero percent relative humidity,and 29.92 millimeters of mercury.In contrast,using the more accurate BC of 0.419 gives a drop of 49.8 inches,a wind drift of 25.7 inches,and an impact energy of 956 ft-lbs under the same conditions."

They end by stating:

"In conclusion,under realistic field conditions,BCs can depart significantly from manufacturers published values,some by nearly 25 percent.Bullets also exhibit shot to shot variations of 1-5 percent in BC that suggest an inherent accuracy limit in predictions based on BC measurements.It should be noted that the BC can depend on the muzzle velocity and on the particular firearm used.If a BC is needed with less than 5 percent uncertainty,the BC should be determined with the same firearm."

Wow :shock: ,worth reading and thinking about by everyone who shoots-and certainly if you shoot long range.
' Be Careful ' out there.Good hunting!
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Tim Anderson
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Re: 'BC' again

Post by Tim Anderson »

I knew about that for sometime, thats why i pick a bullet weight that i intend to use and then get 3-4 different brand of bullets and test them past 300 yards. Best group with highest vel. wins..
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Dcoy
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Re: 'BC' again

Post by Dcoy »

Good plan Tim.
Tyrant

Re: 'BC' again

Post by Tyrant »

Boolit makers ALWAYS fudge thier numbers, My Pact Chrono will figure BC but is a pain to set up @ 100 yds. Nothing advertised is perfect.

I use BC as a good starting point ( decision ) to try a projectile. Tim is appsolutly correct in the best way to determine what shoots well is to fling some downrange..... I also like to load until I see a smidge of Pressure....

My new passion is the 75 GR V-Max Moly with a BC of .435. Based on FPS of 3600 out of my 22-250 AI with a 1-8 twist Pac-Nor. JBM calculations puts me really close out to 500 YDS right now need to shoot paper alittle further to verify come-ups.... Oh and the good news is I'm ALONG way away from Pressure. Anyhow .435 is close enough that the software can accuratly calculate trajectory. I'm happy and I will probably not set up my chrono @ 100 yards to verify BC as it's PFC.

Again my .02 $

Norm
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xdeano
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Re: 'BC' again

Post by xdeano »

This is why it's so important to actually shoot at the ranges that you intend on. Keeping an accurate journal with the atmospheric conditions at the time helps when you need to get your ducks in a row. Heck from 70 degrees to 50 degrees ambiant air temp, my bullet drops about 2 MOA more at 1000yds, and thats only 20 degrees spread. Not to mention what they're doing at -5. 2 minutes is a miss on a coyote at extended ranges, even at 400yds that's 8 inches.

xdeano
“It’s better to live one day as a lion, than a thousand years as a lamb.” -Mussolini
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Dcoy
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Re: 'BC' again

Post by Dcoy »

Amen.
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coyotelatrans
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Re: 'BC' again

Post by coyotelatrans »

I read that artical to and some manufactures are worse off than others Nosler seems to be pretty good and I do the same as Tim, 100 yards is only sight in I don't care if I have a .3" at 100 I care about the groupings of 300-500 and I shoot at these ranges with coyote sized targets and then evaluate the bullet, but I can tell the bullets I use are close as using bal programs and them adjusting clicks or mil holdover there darn close and those rely on BC and FPS. I have gotten better groups with "some" bullets at 200 verus 100 telling me they have a higher BC than others that open up more at 200 and 300.

1,000 yard paper punching and winning by group size is a fine art/science as .3" and you could go from 1st place to 3rd place depending on who is shooting. I want a bullet that duplicates itself time and again out to 600 for coyotes and those that can give me the confidance should I need to shoot one that far to make the shot.
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lyonch
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Re: 'BC' again

Post by lyonch »

You guys aren't relying on the manufacturers ballistic coefficent are you???
Chris Lyon


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My heart belongs to my family,
BUT MY SOUL BELONGS TO THE COYOTES!!!
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coyotelatrans
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Re: 'BC' again

Post by coyotelatrans »

To start with yes, as why would I want a low BC bullet or give it a chance if I'm looking for something consistant to 600 yards? You can tell by the shape and design of bullets what the thought process was behind them when made.

As stated in the artical some bullet makers get real close and I know Berger is redoing there entire BC formulations to give them a more real in the field rating. Nosler has been real close I have found and so has hornady. Barnes seems to be the most off with their ratings. AS they will tell you they make hunting bullets and not match type bullets.

Bullet construction and accuracy has come along way in the last 20+ years for sure!
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lyonch
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Re: 'BC' again

Post by lyonch »

Here's why i asked if you used the advertised ballistic coefficent for a bullet. If you were to do this right and you want an actual B.C. of a bullet you need to first set up two chronographs an x amount apart. Then you need some instruments to read the temperature, relative humidity, the atmospheric pressure,and note what elevation you are at. After all of this is recorded over several shots you then need to bring all this information to your handy little computer program that calculates B.C. and it will tell you what the actual B.C. of that bullet really is. I think it will be to your suprise as to how much this changes from the advertised B.C.
Chris Lyon


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My heart belongs to my family,
BUT MY SOUL BELONGS TO THE COYOTES!!!
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coyotelatrans
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Re: 'BC' again

Post by coyotelatrans »

But many are close at least the ones I use and out to 600 yards on critters and not worrying so much about paper. I run them through a bal program once they show promice and the amount to adjust from the chart in "most" is within a few clicks at best. Some proclaim more than others no doubt and at extended ranges they are off but unless paper punching at 600-1000 most advertised BC's are close as long as one does there work at the range and know where they hit. Big differance between 600 yards and 1,000 for sure. But a guy won't know what they will do unless you shoot them at those ranges
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