Weight a factor of BC?

[TBell]

Weight is not a factor. Most ballistic calculators don't even ask weight. BC, velocity and environmental conditions are what matters.

100 gr bullet bc of .600 and a 200 gr bullet bc of .600 will act exactly the same under the same conditions.



Hope that answers your question.

Show me that in a ballistic table, mass and Inertia matters

 

[VLD Pilot]

Weight is not a factor. Most ballistic calculators don't even ask weight. BC, velocity and environmental conditions are what matters.

100 gr bullet bc of .600 and a 200 gr bullet bc of .600 will act exactly the same under the same conditions.



Hope that answers your question.

I think this question has been answered properly already but I had to chime in on this 100 grain .600 bc vs 200 grain .600 bc comment. Certainly not going to make it an argument but I use to believe that theory until I put it to the test at 1800 yards. Shooting both my 338 Lapua improved with 300 grain Berger's and a buddy's 30/338 improved with 250 ATips. 300s at 3000 fps and 250s at 3200 fps. Winds were pretty gassy and shooting both rifles with zero windage, my 300 grain bullets held wind better with equal BCs. His was the faster rifle at 3200 fps. Heavier even at equal BCs beats lighter when the wind is involved. Took me many past arguments to realize that. In the end, I have been wrong by letting theory steer me to my conclusion. When winds aren't a factor, I'll shoot my heavy 7s over my 338s any day.

 

[ndking1126]

I think this question has been answered properly already but I had to chime in on this 100 grain .600 bc vs 200 grain .600 bc comment. Certainly not going to make it an argument but I use to believe that theory until I put it to the test at 1800 yards. Shooting both my 338 Lapua improved with 300 grain Berger's and a buddy's 30/338 improved with 250 ATips. 300s at 3000 fps and 250s at 3200 fps. Winds were pretty gassy and shooting both rifles with zero windage, my 300 grain bullets held wind better with equal BCs. His was the faster rifle at 3200 fps. Heavier even at equal BCs beats lighter when the wind is involved. Took me many past arguments to realize that. In the end, I have been wrong by letting theory steer me to my conclusion. When winds aren't a factor, I'll shoot my heavy 7s over my 338s any day.

Very interesting. Do you remember how much the difference was?

 

[VLD Pilot]

Very interesting. Do you remember how much the difference was?

Nearly one foot. At 1200 yards there was zero difference

 

[VLD Pilot]

Very interesting. Do you remember how much the difference was?

We just shot that range about a month ago. Three times out in wind ranging from 15-30 mph. Shooting at 4x8 drywall and a 4 foot square steel painted white. Groups weren't impressive but they clearly showed how wind effected groups. The A Tip has a much better published BC than the Berger and moving faster. Couldn't find 338/300 ATips for the test.

 

[ndking1126]

Nearly one foot. At 1200 yards there was zero difference

Did the bullets loose velocity at the same rate? A slower velocity of one compared to the other would cause for a lower BC and therefore more wind deflection. I'm not all that familiar with the ballistic specifics of those two cartridges.

I was thrilled when I found a thousand yard range within 2 hrs. 1800 yards would be fantastic!

 

[VLD Pilot]

Did the bullets loose velocity at the same rate? A slower velocity of one compared to the other would cause for a lower BC and therefore more wind deflection. I'm not all that familiar with the ballistic specifics of those two cartridges.

I was thrilled when I found a thousand yard range within 2 hrs. 1800 yards would be fantastic!

The 30/338 needs alot less elevation for that range. Obviously it maintains velocity better. Faster with high BC. My 338 needed 7.5 more minutes of elevation at 1800 yards. The calculator said the 250 ATips needed 4.5 minutes less wind but turned out it needed a hair more windage than the 300 berger.

 

[Treeslug]

You guys made me think (ouch) ...

I think we have a bit of a "both right" scenario going on here ...


Hypothesis to be proven or challenged:
If the BC of 2 different weight projectiles is the same - their flight characteristics are the same regardless of their weight (i.e. same drop at 1000 yards)

Here is the (simplified) equation used to calculate a bullet's BC (based on the wiki page):



BC(projectile) = Mass(projectile) / [Diameter(projectile) ^2 * i(coefficient of form)]


So, that which makes up the BC for those projectiles is in fact a factor of Mass - as well as Diameter and their coefficients of form ...

So, from what I am understanding (so far) on this - 105g 6mm w/ BC of .6 (making this up) and a 140g 6.5mm w/ BC of .6 (making this up) should both exhibit same drop across their path as long as their muzzle velocity is the same ...


So to see if this is correct, I plugged these two into the Hornady G1 calculator ... both with .6 G1 BC ... both at 3000fps muzzle ... leaving everything else the same and only varying the weight and ...

Drum roll ...

... Both have 7.2 mils drop to 1000 - spot on the same

My conclusion - weight/mass is a factor in what the BC actually is - however - for two different weight bullets with the same BC, their drop will be equal if fired at the same velocity.

Somebody correct me if my logic is wrong?

I would correct you, but I do not understand anything you said.

 

[Pinoniper]

This.

Ballistic Coefficient

 

[ButterBean]

Every thread these days end up just like this one

 

[VLD Pilot]

Ballistic calculators are wonderful for getting the drop very close IF all the numbers are real numbers( velocity, BC, weight and altitude). What's not going to matter in that formula is environmental conditions directly speaking of wind velocity. I don't live in a state that offers good LR shooting options. 1000 yards isn't too hard to find but doubling that is pretty tough. I had to find a place and groom it for that. Winds also aren't a big problem here most of the time. I can pick good days easily. Early and late always gives opportunity. No matter what the print says in and publication, it doesn't account for environment completely. Altiltude, temp and barometer are easy and even tho in theory windage is calculated in programs, it's not close to being accurate in most cases. To see the real results, shooting in those conditions is pretty necessary. Even shooting a 6.5-284 with 147s at 1500 yards vs a 284 with 180s, with both having similar ballistics out to that range, wind will call the calculator a liar Everytime. The 180s will always beat the wind better than the 147s. Wind meaning 15-20mph. At 10 or under, the difference is little.

 

[Pinoniper]

What we are grappling with is actually, "is sectional density a factor of B/C?" The answer is absolutely yes; it's right there in the formula for B/C.

 

[ButterBean]

What we are grappling with is actually, "is sectional density a factor of B/C?" The answer is absolutely yes; it's right there in the formula for B/C.

I agree, It's really simple, the question has been answered yet here we are

 

[ndking1126]

I agree, It's really simple, the question has been answered yet here we are

All thats left at this point is for the thread to be resurrected in 6+ years. Haha

I think we've been conditioned to see all responses as argumentative. It's all good though, the follow on conversation usually has helpful info mixed in too.