How to Calculate Lead Bullet BC?

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Idaholewis

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This is something that i have wanted to learn, But never have. I have looked at a few different Calculators But they Confuse me? I am NOT a Math Guy, I have failed it miserably all of my Life, if i can’t use a Calculator i’m in Trouble :) You guy’s that know how to do it, Please share how
 
The best way is to shoot through a chronograph both up close and at 100 yards. You adjust the BC to natch the speed at 100 yards.
I'm kind if chicken to shoot through my Ohler 35. Those are expensive..
 
Do you think you could get close with a 100 yard zero, muzzle speed, and bullet drop at 300 yards?????
 
Do you think you could get close with a 100 yard zero, muzzle speed, and bullet drop at 300 yards?????

That was what I did with my 500 S&W bullets and my RCBS 11mm bullets. I'm not saying they are spot on but close enough for under 300 yards.
If a guy is going WAY beyond 300 and want to perfect the BC a Chronograph is necessary.
 
I‘m not afraid to put my Chronograph in “Harms way” :D I hate the darn thing, it’s been a Piece of Junk from Day 1, I do believe it gives accurate readings, The problem with mine is after you turn it off, and then back on later, it will literally change Numbers to something COMPLETELY different? Say i put 2 Shots over it and they Read 1,358 and 1,364 When i get home and turn it on to Read them they might be 326, 884 Etc. It’s an absolute Joke

When i do use my Chronograph, I make darn sure and Write each Shot Down on a Note pad
 
I would try it at muzzle, 100 yards and at 200 yards. Preferably at least 5 shots each. Discard high/low. Average the remaining three. Using those averages from 3 ranges you should be super close to real world BC.
http://www.jbmballistics.com/cgi-bin/jbmbcv-5.1.cgi
If say you are 1350fps at the muzzle and 1200fps at 300ft....that is a calculated .323 BC. If your MV velocity is at 15ft from the muzzle just set the far to 285ft.
 
I have used a ProChrono and a Magnetospeed simultaneously to determine B.C. They record speeds within 10fps with each other. Making certain a rifle is shooting good groups, the ProChrono is placed in front of the target and speeds are recorded. Then I go to a B.C. calculator. It's surprising (and usually disappointing) to compare real world B.C.'s with those advertised.
 
Is BC, Ballistic Coefficient, the efficiency of a bullet's flight? If so, what exactly is being measured?

Thanks
 
Bruce,
I would think it would be, most importantly, wind drag. How efficient is the bullet at overcoming this. I’m sure other factors come into play such as kinetic energy etc...
Take two bullets with the same diameter and nose design, make one longer and heavier and the BC goes up. This would be due to KE as the wind drag would be close to the same, actually a little higher because of the extended length, but the increased KE of the projectile overcomes the increased drag yielding a more efficient flight.
Gravity is the only constant in the scenario, once the bullet leaves the muzzle it starts falling, and falls at the same rate of speed regardless of how fast its traveling. The sooner it gets to target, the less it falls.
NASA understands this concept very well, I don’t. Anyone ever figure the MOA of a target such as the moons gravitational pull compared to the earths distance from it? I bet it’s pretty dang small.
I believe a perfect, un-affected bullet would have a BC of 1.0 and only be affected by gravity, but that’s just a guess.
 
Apparently ballistic coefficient puts a number on how well a bullet resists air friction.

Without air one doesn't need to know anything about ballistic coefficient, because bullets wouldn't slow down. Bullet flight would be determined by muzzle velocity, and the amount of up aim. The acceleration of gravity would be the same on all bullets, and no bullet would slow down due to air. For each bullet with equal muzzle velocity to reach the same target, all would require the same exact up aim, because all bullets would fall/fly the same.

Knowing the ballistic coefficient allows one to use math, and calculate the flight path of a bullet flying through the air.
 
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I believe a perfect, un-affected bullet would have a BC of 1.0 and only be affected by gravity, but that’s just a guess.
Nah we have 50 cal and .416 projectiles in the 1.100 g1, I think in G7 a 1.00 is perfect but I am not sure to be honest. I just know my 285 flat lines in my 338 lapua has no hold over to 500 yrds on man sized targets.
 
After re-reading, if you’re asking for how to calculate with a calculator- I’ve found years ago after talking the Mr. Oehler and another conversation with a Speer Tech, it’s nearly impossible. Speer uses their own proprietary program.
The basic formula is: bullet shape / (weight x diameter2)
Obviously it’s bullet shape that is hard to ID a numerical value.
Good luck
 
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