BC. How does weight affect it?

[Cold Trigger Finger]

  So,  here's my?
 Since lead is dense and a longer bullet given equal shape would have a higher BC but it would also weigh more. 
 With high BC bullets like the Cutting Edge or the GS Custom  how does their lighter weight affect their drop and drift at long range? 

[swampthang]

thats a good question, it can work 2 ways, sleeker,faster to target , less effect.
or heavier, maybe a little slower but more mass to buck the wind. im waiting to see what others post. i have my own theory but keeping my mouth shut for now. i like faster to target but also like mass to.

[Cold Trigger Finger]

 Yes,  there are quite a few points to consider.  Higher velocity verses greater momentum.

[Rooks]

So, p=m*v
If you double the velocity you will double the momentum of an object and if you double the mass you will double the momentum. Momentum is directly proportional to an object's mass and directly proportional to the object's velocity.

If we have increased momentum it would take more time (distance=rate*time) for the bullet to be affected right?
I'm just throwing some stuff out there that I am pulling from my physics class a few years ago...

[swampthang]

damn rooks, were you a professor?
thats DEEP!  lol

[Cold Trigger Finger]

 OK.  But.  ( for starters,  what is the p signifying?)  And since we are not doubeling anything and I more than suck at calcalations. 

[Rooks]

Haha, No professor here. "P" is momentum, sorry.

Trigger, Earlier you mentioned "Higher velocity verses greater momentum." What I was pointing out was, if you double your velocity (like swamp likes) you can double your momentum which in turn should cause the bullet to require a larger external force (wind) to affect it.

BUT, does increasing momentum increase drag? And gravity is always a constant (9.8 m/s squared, down to earth)

And does going beyond the speed of sound change the drag? (Speed of sound~340 meter/second = 1,116 feet/second at sea level). Hypersonic is 5x's the speed of sound. Are there any bullets that do this? I know my dad's .204 shoots in the 4,000 range. I did some digging and found a website called jbmballistics.com Here is some info from it;

"Bullets of different shape such as round nose bullets, boattail bullets hollow points would all have different drag curves and therefore different drag functions. Because the relation between the standard bullet and other non-standard bullets is not perfect, some manufacturers define multiple ballistic coefficients as a function of velocity to better fit the drag model."
"The ballistic coefficient, is obviously a function of the speed of sound."

Is this any help? haha

[Rooks]

Cold Trigger, I found your answer! I found it pretty interesting. Nothing like a cup of coffee and a Saturday morning to educate the mind on ballistics...

"This rule doe not depend on shape but includes one more parameter than Greenhill's Rule, the easily obtained weight of the bullet m. It is based on correlating experimental bullet data obtained at the US Army Research Laboratory (formerly Ballistic Research Laboratory)."

http://www.jbmballistics.com/ballistics/bibliography/articles/miller_stability_1.pdf

[Darkker]

CTF,
To your original question, weight is related, but only.
The answer is, "IT DEPENDS".
Barnes copper bullets have a high BC number for weight because of the copper. It's less dense, so the bullet gets longer than a same-weight lead core; this ups the BC.

Then you have construction to play with. Sierra's 155gr palma bullets, are essentially as long as the 175 SMK's. Different ogive and tails.
... so kind of like folks who want to know case volume, but weigh brass; BC & weight CAN have a connection, but you have to assume a lot because there are so many different factors.

[Cold Trigger Finger]

 OK.  So it seems that without shooting them I won't truly know.  The GS Custom. 264 ,112 gr SP bullet has a BC that is as high as several different 140 gr 6.5 target bullets.  The 133 gr Cutting Edge MTac  6.5  does also.
 I was wondering if anyone knew more about obtaining G7 BC on these bullets.  And,  if these bullets especially the 112 SP acted differently than a 140 because of its lighter weight. . As far as retained energy,  drop and drift. 

[Rainier]

Here's something to ponder about momentum - if you shoot a .30 cal 180gr bullet at 3300 fps and a same shaped 220gr bullet at 2800 fps - which is traveling faster at a 1000 yards and why would that matter?

[Cold Trigger Finger]

 . ??

[Rainier]

Too funny - bottom line the 220gr bullet will be traveling almost 200 fps faster then the 180gr bullet even though at the muzzle the 180gr is traveling 500 fps faster. Why should it matter? You destabilize a bullet when you enter the transonic barrier. So the question becomes how far are you shooting? What's the purpose for the rifle? 1000 yard matches or 600 yards coyotes or, or, or...

Then there is the question of time to target. The faster you get a bullet to a target the less elevation and wind adjustment you have to make, so can we get enough muzzle velocity to keep a 112gr SP supersonic at 1000 yards? Hell if I know but I'm gonna try

[swampthang]

ok here's the bottom line:
im just an ole bench rest shooter that has been lucky enough to have success but this conversation is like ebonics and Chinese mixed so im just gonna stay my ols ass out of it and do A WHOLE BUNCH OF READING AND LISTENING!

[Cold Trigger Finger]

Well Tony,  that ain't fair.  I mean you actually shoot at stuff a thousand yards away.  Maybe I'm just convoluted but like with your tactical rifle,  how do you work up a fireing solution??
 
 So let me take a stab at this?  from another angle.

 2, 6.5 bullets with the same length and shape.  One is made from copper the other has a lead core and gilding jacket.  One starts out at 2800, the cup+core and one starts out at 3200 , the mono.  Will gravity or forces,  wind,  mirage cause both to drop the same?  Will the heavier weight of the 140 cause it to surpass the 112 at some point given that they have near identical exterior shapes???