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Heavy Bullets!

 
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  #22  
Old 06-26-2012, 10:42 PM
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Re: Heavy Bullets!

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Originally Posted by angus-5024 View Post

I just want to thank both Broz and LTLR for there insight into this. Two very knowledgeable shooters who have more than theory behind them. Thanks for your time guys!
Ditto Angus' remarks. As a side remark to what you said, the numbers in a ballistics calculator are only as good as the equations themselves and the variable inputs. I haven't played with a lot of ballistics calculators, but when comparing 3 or 4 different calculators I often come up with different values (often within .2 MOA but different nonetheless) which tells me that each calculator is probably using a different version of a general equation.

I also agree, that at normal ranges (for me less than 600 yards) the lighter faster bullets seem to be easier for me to make hits with, but as I extend the range past 600 the heavies seem to make it easier for me. I have not done enough real shooting beyond 600 though to have enough data to support what I feel but I do feel the heavy bullets make the longer shots easier.
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  #23  
Old 06-26-2012, 11:01 PM
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Re: Heavy Bullets!

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Originally Posted by angus-5024 View Post

So we can saflely say that two objects of identical shape will fall at the same rate, but when a force is applied to them (wind), the lighter one will be affected more.

The catch is that two bullets having the same b.c, one being heavier, will not have the same shape. The heavier bullet has the momentum advantage, being able to use that momentum to "plow" through its medium (air). However, that advantage could be offset by velocity for awhile, but eventually the heavier bullet will catch up.
I think this is well stated and brings one important thing to the discussion. We do input BC, bullet length , weight, diameter into a program for a correction and to model the drag. But I feel actual shape has something to do with all this too and is sometimes over looked. We all like to think the sleekest looking bullet is best. But is it? This is why I say test them. The proof is in the pudding. What ever the reason is. Hits closer to the point of aim is what I seek.

Jeff
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  #24  
Old 06-26-2012, 11:51 PM
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Re: Heavy Bullets!

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Originally Posted by Long Time Long Ranger View Post
On a ballistics computer enter data for two bullets with identical ballistic coefficients. One bullet at 150 grains and the other at 300 grains weight. With weight being the only change in the data. See what the results are. The two will probably be identical no matter the weight entered.

I don't think I forgot any important factors in the equation. The same bc should fly the same. The key is finding the best velocity/BC combination with adequate weight/construction to do the job. A heavier bullet will not drift less just because it is heavier.
I'm going to have to disagree with you as well on this point.

The heavier an object is, the more force it takes to cause a deviation in it's flight path.

Thus when you compare two bullets of any given caliber of the same design traveling at similar velocities, the drift of the heavier bullet is going to be less with the same wind velocity and range.

What little tinkering I've done also shows that with different calibers comparing bullets of the same design shows the same thing unless you are running the heavier bullet at a much, much slower velocity which then allows for dramatically increased flight time which then allows the same wind to act on it for a much longer period of time than the faster smaller bullet.
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  #25  
Old 06-27-2012, 12:02 AM
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Re: Heavy Bullets!

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Originally Posted by Broz View Post
Browninglover, Thank you for the analogy. It helps to explain what and why the test results are what they are. All I know is what I have seen and what works for me.

Thanks
Jeff
I don't think that problem is as severe as it used to be. When for example the first bans on lead shot came out we quickly discovered that Steel just didn't cut the mustard because it was less dense than Lead.

Similarly with the early monometal bullets it didn't matter how the bullet looked you just couldn't get the same density in the same sized projectile as you could with traditional bullets.

When we look today at the SD's of the modern monometal bullets they are indeed much, much better but they still just don't seem to fly quite as well as the lead/copper jacketed bullets.

One problem we get into in these discussions is that the average shooter cannot shoot well enough to do a true side by side comparison because they either lack the skill or the equipment for true precision no matter what they are shooting.

It's a very, very small percentage of shooters that have both the skill and equipment to really judge the differences in bullet performance especially at long range.

We are really fortunate here to have quite a few people who contribute to this site that have both which makes it a great resource.
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  #26  
Old 06-27-2012, 01:05 AM
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Re: Heavy Bullets!

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Originally Posted by Browninglover1 View Post
I'm not being a jerk when I ask this, but do you have an article I could read that talks about how BC's are computed? I remember reading an article in Shooting Times many years ago that said BC's are calculated off of the G1 drag model that only takes into account a bullets shape. The problem with the low drag bullets is that they are so far removed from the standard G1 model that results can be drastically different depending on what velocity you are shooting the bullets at. That is supposedly the reason that the G7 standard was developed because it computes a number based of a model that much closer resembles the actual low drag bullets.

Again, I don't want to sound like a jerk but I would really like to understand. Like I said, I understood that BC's were computed off the "drag factor" determined by bullet shape and had nothing to do with weight, but I could definitely be wrong.
BC's are calculated in different ways.

Hornady's 8th edition reloading manual has a couple of chapters that explain in some detail ballistics including how BC's are computed.

There are two basic ways.

Once is Drag of a standard projectile divided by drag of test projectile.

The other is more complex where you have:

BC= WID2 (D squared) where
W=mass in lbs.
I=coefficent of form factor
D=Bullet Diameter (measured in inches).

In short both methods tell you how efficiently a bullet will fly at a given velocity.

BC's are not however static as they change as velocity changes.

Bullets that fly the most efficiently at high velocity tend to destabilize when transitioning from Supersonic to Subsonic speeds.

Bullets designed for subsonic stability will not fly well at all at supersonic velocities.

Think about a Piper Cub and the SR-71. The cub flies great and is extremely manueverable at low speeds, but would tear itself apart if you you pushed it beyond Mach 1.

The SR71 flies at Mach2 plus extremely efficiently but cannot fly at all at low speed.

Calculated BC's are very helpful in picking bullets, but the highest BC will not always be the best bullet for every application.
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  #27  
Old 06-27-2012, 02:04 AM
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Re: Heavy Bullets!

The G1 model bullet weighs 1 pound ( 7000 grains ) and has a BC of 1.
So if a bullet has a BC of .5 it flys with 50% of the efficiency of the G1 bullet.
So if weight is the most important factor in a bullets performance with a .5 BC it should weigh 50% of the G1 bullet , 3500 grains ????
However there is a few .5 BC bullets out there that only weight upto 400 to 500 grains , that is only about 15% of half the weight of the G1 bullet ???
So is weight the most important factor ?? I am not saying this is right . I am just saying that it seems queer to me.
I do the ballistic calculations and the heavy ( longer ) bullet seems to exhibit the least amount of windage .
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  #28  
Old 06-27-2012, 02:13 AM
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Re: Heavy Bullets!

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Originally Posted by Bullet bumper View Post
The G1 model bullet weighs 1 pound ( 7000 grains ) and has a BC of 1.
So if a bullet has a BC of .5 it flys with 50% of the efficiency of the G1 bullet.
So if weight is the most important factor in a bullets performance with a .5 BC it should weigh 50% of the G1 bullet , 3500 grains ????
However there is a few .5 BC bullets out there that only weight upto 400 to 500 grains , that is only about 15% of half the weight of the G1 bullet ???
So is weight the most important factor ?? I am not saying this is right . I am just saying that it seems queer to me.
I do the ballistic calculations and the heavy ( longer ) bullet seems to exhibit the least amount of windage .
Weight is but one of the factors in the equation, but when it comes to resisting cross winds it's extremely important.

The heavier the object in flight is, the more energy it takes to force it from it's initial flight path.

The amount of force exerted against that bullet is a function of wind direction, speed, and duration of time of flight.

The profile of the bullet also comes into play as a long, streamlined bullet presents less surface area for the wind to work against than a big fat flat or round nosed bullet.
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