Do you consider Sectional Density when choosing a bullet?

Old rooster

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Is sectional Density a true way to tell in advance if a bullet will perform well?

There are believers and disbelievers
 

WeekendWarrior

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Sectional density and the shape of the bullet are the two factors that determine the aerodynamics of your bullet, so particularly at long range it matters. It is important to note, excluding the comparison of a monolithic bullet to a lead core bullet, the section density amounts to a longer and skinnier bullet and thus usually (note the use of the word usually... dang hair splitters) higher BC and improvements in other measurements of aerodynamics. People will split hairs comparing bullets of similar grain and caliber, but people will be people, and by the time the argument gets to this point, the performance of the bullet is probably going to be user and rifle dependent anyway.

edit: the improved aerodynamics usually means a flatter shooting bullet at longer distances (lots of air traveled through, think 1000 yards+), preserved energy at longer distances (less energy lost to penetrating air), and assuming the barrel twist and powder charge is appropriate and comparable to bullet of lower sectional density the bullet should remain supersonic longer and more stable in flight (spinning and not tumbling) and thus improving accuracy as well.
 

MagnumManiac

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Here we gooooo.....
Popcorn?
Can’t handle popcorn kernels shell stuck between my teeth….I’ll pass.

No, I may look at sectional density in passing, as it is written in every loading manual I have, but it does not influence my decision. Construction, BC and the GAME influence my choice.
I am a fan of bonded sleek bullets, tried Scirocco’s, they are softer than Accubond and perform well, Accubonds, ABLR, Berger Elites (if they will ever be available here again) Speer Hot Cor and Grand Slam or even Woodleigh are what I look for.
Have used Sierra and Hornady, but these were lacking for me, just not the performance I am used to.
I really like Ballistic Tip Varmint bullets in my 22’s and 25’s, they are stupid accurate too.

Cheers.
 

jebel

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No.

Sectional density takes into account only diameter (caliber) and weight. Not bullet construction, composition, design, or velocity at impact. In other words, it disregards all of the important elements that distinguish bullets, particularly the different ways they react after striking a target. I would recommend disregarding it.
 

Hand Skills

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Sectional Density matters in a world of non expanding solids, but throw expanding bullets into the mix and it goes out the window.

In the context of terminal performance, SD is becomes dynamic and drastically diminishes as a bullet mushrooms (increases diameter) and fragments (loses mass).

Then there is the problem of materials. Tungsten, copper and lead all have very different densities, yet all.308 200gr bullets have the same SD - doesn't matter what they are made of. Compare a 200gr copper mono to a 200gr Hornaday RN interlock. The all copper bullet is significantly longer, and has significantly more displacement.

We see time and time again that bullet construction plays more of a part in penetration than mass.
 

Old rooster

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I agree guys,I know what sectional density is but to me is an abstract number.
For instance,a 9mm 147 gr bullet has a sectional density of 167 while the 45 acp 230 gr bullet has a sectional density of only 162!
If these numbers were real world indicators of lethality the 45 acp should have the larger number as it much larger and was designed by the military to stop a charge or even knock a charging enemy soldier backwards when shot.
Who in their right mind would want a 9mm over a 45 acp in battle?
Chuck Hawks mentioned this as his argument about sectional density and I was just wanting to hear others thoughts.
I consider B C way more worthy of mention than sectional density
Thanks to all
 
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Hugnot

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yes

SD = bullet weight/7000 /(diameter^2), SD = sectional density

BC = SD/FF, BC = ballistic coefficient

FF = SD/BC, FF = form factor

Both BC & FF are dependent on SD, sectional density and use G7 bullet shapes.

Evaluations of bullets that fly real good have FF's under 1.0 and less, compare SD and BC, look for SD's that are smaller than BC's resulting in lower FF values. Like a FF value of 1.005 would have .5 % more drag than the standard bullet. Like a FF value of .995 would have .5% less drag than the standard bullet.

This has evolved into real pointy low drag bullets having high G7 ballistic coefficients. Everybody loves high BC bullets and scanning bullet specs is common for selection.

SD is a valuable consideration for selecting pointy bullets that fly good. Should 2 bullets have equal BC values, the bullet with the smaller SD would have less drag and fly better. In addition, the bullet that weighs less can be driven faster.

Post impact bullet destruction causes desirable aerodynamic qualities to go away. A post impact high SD bullet would penetrate better - provided - the bullet weight would be retained after impact and the diameter would remain constant. SD = bullet weight/7000 /(diameter^2), as the diameter increases the SD decreases, as bullet weight decreases (fragmentation) the SD decreases.

I like shooting my .45 Auto, 1911 because it makes big holes in things.
 
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73driver

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I do not look at SD in particular. I for my own reasons like heavier for caliber bullets. Example, in the 30-06 I will go 180/165 grain bullets over the 150's. In the 270 I will take the 140/150's over 130 grain bullets. In like for like bullets, be it a Sierra GK or a Nosler LRAB the heavier bullet has more punch and better BC than lighter bullets. I think of it as trading near range velocity with a lighter bullet for longer range punch with no loss of drop or velocity at longer range vs the lighter bullet. Finally a heavier bullet with better SD is more likely to pass through game than a like constructed lighter bullet.
 

bengineer

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SD changes when a bullet changes shape.
In theory, we usually want hunting bullets to travel happily, without deviating from our preferred flight plan or moving lots of air, and then change shape to displace lots of tissue. Thats a tall order, one a simple ratio cannot address unless we limit our input variables to two: change length and weight with similar construction. Well, thats boring, and prevents SD from being useful when comparing bullets of different construction.
So, take a look at bullet construction. Look at materials used and the thickness of the jacket, depth of hollow point, look at expanded bullets and see what they turn into. Then compare to what you want a bullet to do. For example, most avoid a RN form for long range. But if you could hit with a soft RN at distance, you may find that form to readily expand. But, it may expand wide and not penetrate deeply, maybe even causing harm but not killing. But a soft, sleek pointy bullet would fly flatter and hit faster, maybe causing the bullet to expand in such a way as to end up with a narrow “mushroom,” allowing deep penetration along with rapid expansion. Those are two quite different results and SD may calculate to be identical on both.
SD and non-expanders was mentioned previously in post #6; that post is spot on.
 
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antelopedundee

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No.

Sectional density takes into account only diameter (caliber) and weight. Not bullet construction, composition, design, or velocity at impact. In other words, it disregards all of the important elements that distinguish bullets, particularly the different ways they react after striking a target. I would recommend disregarding it.
Yep. A 180 grain .308 spitzer, a 180 grain .308 RN, a 180 grain .308 VLD bullet and a 180 grain .308[copper or lead] cylinder all have the same sectional density so which one to choose for that 1,000 yard shot.
 

Old rooster

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Does anyone use a ballistic app that asks for SD?
Mine does not but someone at a gun counter at a local shop said his did.
From a ballistic app standpoint could it make a difference?
 

xsn10s

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Does anyone use a ballistic app that asks for SD?
Mine does not but someone at a gun counter at a local shop said his did.
From a ballistic app standpoint could it make a difference?
Not that I've seen. Maybe the person confused standard deviation for sectional density. I haven't seen any ballistics app ask for either value.
 
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