Is SD (Sectional Density) by itself Worthless?

[muledeerarea33?]

Sierra game kings have done me well in several calibers. I love looking at the data but I use the bullet that puts the most blood on the rock.

[308Nut]

I think you need to re-read my post very carefully and then read some of your response to my post. You say things like "but you might have meant that too", when it was stated right in the quote. I didn't just mean it, I actually stated it exactly.

 

If you're going to argue that sectional density doesn't contribute to BC, go above me and talk to Sierra Bullets. They'll set you straight. And fast.

 

My example of the jacketed lead versus the all copper was to illustrate that SD matters regarding BC. Visualize 2 bullets that have identical diameters, nose profiles and boat tails. They both weigh the same. 200 grains for this example. One is all copper. One is jacketed lead. Can they have the same overall length? No. The all copper bullet will be longer because lead is 'denser' than copper and it takes more material to make it weigh 200 grains. Maybe my choice of words, namely mass was poor. Nevertheless, the copper bullet is dimensionally bigger which creates more what?? Air drag, giving it less of a BC because the form factor is less due to the increased length.

 

Now let's visualize that the two bullets have the exact same dimensions. One being all copper, one being jacketed lead. Which has the higher BC? Answer: The jacketed lead version. Why? Because it has a higher what?? Sectional density...In addition, which will (all else being equal) penetrate more? Answer: the one with higher sectional density.

 

Is SD all important? Maybe not. Is it worthless? No.

 

Are you trolling?

 

BTW, I wasn't defending Berger in the least.

[.270]

I understood ya. But I'm purty smart. Lark

[DesertBull]

I've only had a couple of experiences with all copper bullets but both were disasters.

[MMACFIVE]

308 nut: you said, and I quote "Also, 2 bullets that have equal caliber and form factor but have different SDs, which do you think will penetrate more? Lets pretend that one is a FMJ and one is a thinly explosive bullet. I think we can have both made with the same form factor and the same SD? Can't we? Then we have to agree that one will penetrate better then the other. So No, equal construction was not "Stated right tin the quote"!

 

And as far as Sierra setting me straight: the 220gr 30 cal round nose has SD of .331 and a BC of .31 while the 220 HPBT MK has a SD of .331 and a BC of .629. So doesn't that actually "set you straight?

 

My main point is that it is not accurate when a posters states they would not use bullets X because of SD. If I compare the venerable Nosler partition that has been one of my favorite bullets for nearly 50 years and recognized and one of the best penetrating bullets on the market I know I can shoot a Barnes (or eTIP, or GMX, or) that weights about 30% less and still get nearly the same penetration because of "Post Expansion SD". We could get on a tangent about BC vs Velocity, vs wind drift here if we want to go on a tangent but that was not my intention of the post.

I am not Trolling. I am not telling anyone they should be shooting one bullet or another (although we have killed nearly 60 javelina, Deer, Antelope, Bighorns, Elk, and other big game animals with Barnes and have never had a single bad experience so I have complete faith in them. I also like speer, nosler, and hornady, among others. I am suggesting to not base penetration on SD alone!

And 270: I kinda have to question you last statement.

[308Nut]

Sierra would still set you straight.

 

You're example of the round nose versus the spitzer having equal SDs but the round nose having a lower BC is true. Understand that I never said BC was based on only SD. Yes form factor is key as your example shows. But you need to realize SD plays a role too. Again, if you have 2 bullets shaped exactly the same (same length, nose, boat tail etc..) but one has a higher SD, it also has a higher BC and penetrated more. These are inescapable truths in physics and science.

 

What is SD in relation to bullets? It based on diameter and weight. Is weight important?

[.270]

Oh well. I don't hafta prove anything to anyone. 'Specially not you. Been reloading over 50 years. Done an' lurnt me a few thangs. I know this much about sectional density. It must mean somethin' er nobuddy'd care. Run along now. Run along. Lark

[MMACFIVE]

308,

 

I think we are closer in thoughts than you think. I actually think if everything is held constant, SD, construction, form factor, etc the the BC from any caliber should be nearly the same. e.g all Nosler Accubonds with a SD of .260 should have nearly identical BCs. What do you think? ( and thats' not patronizing!)

[MMACFIVE]

Oh well. I don't hafta prove anything to anyone. 'Specially not you. Been reloading over 50 years. Done an' lurnt me a few thangs. I know this much about sectional density. It must mean somethin' er nobuddy'd care. Run along now. Run along. Lark

I'm just glad none of us are too old to learn something new. When all things were equal, SD was a pretty direct correlation to penetration. Now we have solids, monolithics, explosive, bonded, interlocked, etc so it doesn't' quite mean the same. Even though its been around along a long time other parameters have changed. Heck, even ole Bryan Litz might be learning a thing or two about BCs with Doppler now? So if you can't stay on point or if you just have to be jerk about it maybe you should just stay out of the conversation? SD is just a mathematical expression of weight to diameter. Given equal construction it gives us a reference point of penetration between multiple diameters...so maybe it isn't quite dead yet. Or had you already implied that and I missed it?

[Tucson John]

you guys are hurting my head...........

[ThomC]

The truth is that penetration on an animal is so variable depending on where and what you hit as to be almost a non issue. We are trying to kill them right? But here we have two or more people who have studied the science of bullets and may or may not agree. That is how new stuff get invented. If you all want to discuss this more, I will read it. But, I will need a little salt, maybe some cheese, and a Perfect Manhattan with that.

Ps the word "jerk" was not scientific or helpful. But, if you jerk the gun then all BC SD BS will not make any difference because you missed.

[MMACFIVE]

Thank you, I'll own that....the jerk comment might not of been helpful. But you have to admit previous comments could allow for much worse implications.

 

I don't understand why these forums get so attacking. Why does someone need to prove their mental superiority?

 

Yes penetration on animals is variable. Although this wasn't meant to to be about bullets selection I know that I use a bullets that work in the worst shot locations and if or when I lose and animal it will be on me, not my bullet. You almost never hear someone owing something they did wrong.....its always the bullet.

[.270]

Hahahaha. I get it now. You were joking. I missed it. I usually pick right up on folks joshin'. But now tell me, mmmac (do you stutter?), why "DO" you need to prove your mental superiority? I've always been a c- guy so I don't understand the concept. I can say one thing about .308, whenever I have a question about balistics that I don't know, I ax him. Then I know I have the right answer. Lark

[billrquimby]

I'm with Lark. I don't worry about such things. I have handloaded every round I've ever shot since 1955 and I've shot a huge pile of game using the heaviest Nosler Partitions available at the safest but fastest speeds. The bottom line is that only thing that matters is minute-of-deer accuracy.

 

Bill Quimby

 

 

[.270]

"Minute of deer" is one of my absolute favorite quotes. Purty much splains it all to a hunter. Lark