Heavy bullets vs.light bullets

[Bart B]

Originally Posted by Crazycooydog

Are the balistic programs allways right in the number they show.

No.

The answers each one gives depends on the formulas used in the software coupled with the BC values of a given bullet leaving at a given muzzle velocity. BC's derived from actual time of flight tests between two points are more accurate than those derived from weight and shape.

All bullets have a small range of BC's that vary with the velocity they are moving at. Air flow around a given bullet is not always exactly the same from muzzle to target. Sierra Bullets list as many as 5 BC's for some bullets in 5 different velocity bands. Other bullet companies as far as I know, list only 1 BC for each of their bullets. Sierra's software allows different BC's and velocity bands for each BC a bullet has in each of those bands. I don't think other software does.

In my own tests from measured bullet velocities, sight movements and atmospheric conditions, Sierra's software has produced sight settings for ranges up to 1000 yards within 1/2 MOA of exact for several of their 30 caliber match bullets at different muzzle velocities. For me, that's about as accurate as one can get.

Using a few other ballistic software sets I've tried, the drop numbers vary somewhat compared to Sierra's. Berger Bullets' software is the closest to what Sierra's gives for answers.

Do your own experiments and use what you're comfortable with.

[barnesuser28]

Originally Posted by Bart B

Sierra's software allows different BC's and velocity bands for each BC a bullet has in each of those bands. I don't think other software does.

shooter allows you to enter more than one B.C

[Bart B]

Originally Posted by barnesuser28

shooter allows you to enter more than one B.C

With a high and low velocity limit for each one?

[Broz]

Originally Posted by Bart B

With a high and low velocity limit for each one?

You enter MV and then you enter the BC and a low velocity limit for that BC, then the next BC and also a low vel limit and so on. The last BC entry has to end with a zero velocity. I don't know how many entries you can make but I know I have entered some with I think over a dozen.

Bryans New Applied Ballistics app has that option also and it also has an option to do your own custom drag models too. This is said to be best used for transitioning bullets going subsonic. I have the app but have not yet got familar with the custom drag model option.

Jeff

[Mikecr]

Originally Posted by MontanaRifleman

There are only two things that affect wind resistance. Velocity and BC.

This is wrong, and so are notions of high velocity trumping BC.

Wind drift comes down to Time Lag, and distances wind drift deviations(resulting from time lag) are applied.
The more a bullet SLOWS(decays in velocity) the greater wind influences it's flight.
That slowing rate is tied to BC.
The only time higher velocity 'seems' to reduce wind drift(as calculated), is when BC rises with velocity.
But if your drag curve matches your bullet, BC does not rise with velocity(and drag still does).

Lighter/lower BC bullets slow down at a higher rate at any velocity, and highest near the muzzle. This is one reason near wind matters most.
So provided BCs are valid at velocity, lower BC bullets ALWAYS drift more with a given wind than higher BC bullets, regardless of velocities.

[Broz]

Originally Posted by Mikecr

Wind drift comes down to Time Lag, and distances wind drift deviations(resulting from time lag) are applied.
The more a bullet SLOWS(decays in velocity) the greater wind influences it's flight.
That slowing rate is tied to BC.
The only time higher velocity 'seems' to reduce wind drift(as calculated), is when BC rises with velocity.
But if your drag curve matches your bullet, BC does not rise with velocity(and drag still does).

Lighter/lower BC bullets slow down at a higher rate at any velocity, and highest near the muzzle. This is one reason near wind matters most.
So provided BCs are valid at velocity, lower BC bullets ALWAYS drift more with a given wind than higher BC bullets, regardless of velocities.

Well, Thanks for posting this. I guess I never new the technical reason or how to explain it, but, heavier higher BC bullets have always trumped lighter faster bullets in my wind drift testing in the field. Thats why I go big. Bigger BC, more energy, retains velocity longer and soon becomes the faster of the two and the result is less wind drift.

Thanks
Jeff

[T3-OleMan]

Great explainations. Kinda like the Greyhound bus finally passes the Moped.
Get er done!