Hawkins,

quote:

Does anyone believe that given two identical bullets that the slower one will penetrate deeper ?.

Yes, it does happen. With monometal bullets one needs to go to extremes to get it to happen but with jacketed bullets it is easy to demonstrate. With monos, starting from slow and speeding up, penetration will increase to a point where additional speed starts giving a reduction in penetration depth. On game up to 200lbs, I have never recovered any 40gr GSC HV bullets that impacted at less than + - 3900fps. I have recovered both bullets that were fired where impact speed was over 4100fps.

quote:

Originally posted by hawkins:
Does antone believe that given two identical bullets that the slower one will penetrate deeper ?.
Penetration depends on momentum. A light weight high velocity bullet will penetrate as well as a hevy one. Look at the armor penetrators they are using against tanks.
SD is not a BS concept it is a physical property. It determines the area over which the
momentum acts. That is why they put points on nails.
Good Luck!

Yes indeed, penetration depends on momentum. AND IN ADDITION, ON RESISTANCE TO PENETRATION BY THE TARGET MEDIUM! IF a HV bullet expands significantly, its ability to penetrate decreases in proportion to the increase in size of the front of the bullet (ie., resistance increases).

If two projectiles of the same weight impact at the same velocity, and one is a flat washer and the other is an elongated bullet, which one do you suspect might penetrate more deeply? I'll give you a hint-the penetration of the two will NOT be the same!

Likewise, momentum increases due to a velocity increase, BUT that increase is linear, mass X velocity. But resistance encountered by that bullet increases as thre SQUARE of the increase in velocity - both as it travels through the air, and as it attempts to move through a target. You may have noticed that the faster a bullet is moving when it leaves the muzzle, the faster it shucks that velocity as it moves downrange!

If you give a projectile four times its' original momentum by increasing the velocity 4X, the resistance to its' passage through the air is increased 16 times

If you look at the properties of the depleted-uranium long rod penetrators used in that hypervelocity fin-stabilized armor-piercing discarding-sabot smoothbore tank gun ammunition, their characteristics are completely different from small-arms projectiles. To begin with, their SECTIONAL DENSITY (there's that word again!) is maximized by making them very small in diameter, and constructed from a very massive material, depleted uranium. They have extreme mass distributed over a small area in order to make stopping them very difficult AT ANY IMPACT VELOCITY, and to maintain their initial velocity as far downrange as possible. Due to their hardness, they DO NOT expand on impact-they merely penetrate at the same diameter they were. They are also launched at hypervelocities which are quite beyond the reach of current small arms ammunition technology. I don't believe the same analysis that applies to game bullets works in this example, because beyond a certain level of impact velocity, properties and behavior of both projectile and target change - I am not sure what this velocity level is, but I don't believe we have reached it yet with sporting cartridge designs.

quote:

Originally posted by hawkins:
A light weight high velocity bullet will penetrate as well as a hevy one.

TA DA!! (that is all I've been saying, while incorporating the construction).

quote:

SD is not a BS concept it is a physical property.

I might not have read the whole thread thoroughly but I do not recall anyone saying SD is a BS concept or denying it is a physical property.

/

you really like talking about SD don't you.

Alf,

quote:

it is a fundamental part of the bullet's trajectory in air!
The ability to overcome air drag and to shoot accurately based on the external ballistics part of the equation is related to SD.

Trajectory is determined by BC, MV and a number of other smaller influences.

If the correct way to arrive at the BC of a bullet is: Mass /(Cd x cross sectional area) How does Sd figure in calculating BC?

/

Alf,
Thought so. Every time Sd is held up as a significant entity, it has to be reworked, extracted and made to piggy back on something else to be of worth. However, to return to my original point of view: Sd is worthless as an indicator of likely terminal performance. However, the elements that make up Sd (not the square bullet one, the real one), mass and cross sectional area, are of vital significance. Just why one would use them to arrive at Sd is a bit strange though. Don't you agree?

Open question:

Which one would penetrate the deepest:

a) A round ball weighing 500 grains (poor SD)?

or

b) A bullet weighing 500 grains (better SD)?

Both are fired at the same velocity, made from the same material, the momentum is the same, the target is point blank distance away, and let us assume no further expansion takes place on impact, keeping its pristine shape.

Before answering, consider that the bullet has more weight behind its frontal area than the round ball - termed this way because I do not want to use the word SD again.

Warrior

Ok, I'll play, lets say the velocity is 2 miles per hour. They both suck.

ElDugelo; In your initial post you said the bullets were nonexpanding. Now one is a washer??

Acxtually no one sadi that SD was BS, they did say it was meaningless.
I should know better than to get into these things.
Good luck!

I will play too.

Round ball painted blue and bullet painted red, at 2mph mv, 45 degree downward angle into a bucket of custard at 10" from the muzzle. The bullet will go deeper! What Chris needs to explain is why it goes deeper. Is it because it is painted red or because it has more momentum to apply to it's cross sectional area or because of the higher Sd? Note that the custard must be brought to a consistency that will support both the bullet and the ball if placed on the surface of the custard.

I am glad that there is a muzzle velocity of 2mph because, despite the bullet having a better Sd value than the ball, if both are at rest, penetration of both is the same - nil.

I am begining to get the impression that the bullet penetrates deeper, because it is RED and thus far more dangerous and because the target is CUSTARD, which is softer than flesh and because I am not aware of any rifle in the world that sends projectiles off at 2 mpu.

Perhaps we should return to shooting round balls or even nigger balls just for the fun of it. That way we can eradicate the term SD for ever. Then we can only talk about small balls and big balls.

If we cannot convince the fraternity to follow suite, then I am afraid that SD will be with us forever (and with those looney mathematicians).

Revisit the question .... the momentum is the same for the ball and the bullet !!! The only difference between the two is their SD's and that naturally follows that the bullet's frontal area has been made smaller relative to the round ball that we squashed into bullet form.
Warrior

Chris, Are you saying that the bullet goes deeper than the ball because the Sd is higher?

The bullet goes deeper because Mo/Xsa has been optimised by virtue of shape. We also know that SD is hidden in the above ratio (ratio's provide usefull clues). So it all works together:

SD = Mass/DxD

Xsa = DxD

Mo/Xsa = MxV/DxD = SD x V

Strange that a ratio is of more benefit that any one single parameter.

Warrior

Chris,

quote:

The bullet goes deeper because Mo/Xsa has been optimised by virtue of shape. We also know that SD is hidden in the above ratio (ratio's provide usefull clues).

Thought so. Every time Sd is held up as a significant entity, it has to be reworked, extracted and made to piggy back on something else to be of worth.

quote:

SD = Mass/DxD
Xsa = DxD
Mo/Xsa = MxV/DxD = SD x V

The above are all wrong.
Sd is the ratio of frontal surface area (half the bullet diameter squared, times pi) to bullet mass.
Cross sectional area is half the bullet diameter squared, times pi.
Mo/Xsa is MxV/half the bullet diameter squared, times pi.

The way you work it out implies that you are using square bullets.

Bottom line is that the bullet goes deeper than the ball because of Mo/XsA not Sd.

Don't worry too much about the square bullets its not a major issue. I stand by my conviction.

This is what HenryC470 wrote on 10 Feb 2005:-

[Qoute]The ratio of momentum to cross sectional area is exactly equal to the velocity times the sectional density.

(m x v)/A = (m/A) x V

Where m is the mass of the bullet, v is its velocity, and A is its cross sectional area. The two derived quantities you are arguing about, momentum and sectional density, are the product of the mass with the velocity and the ratio of mass to cross sectional area, respectively.

momentum = m x v
sectional density = m/A[Quote]

The "square" bullets won't hurt the barrel.

Warrior

And is your conviction that the bullet goes deeper than the ball because of higher Sd or higher Mo/XsA?

I thought I have expressed myself very clearly, but obviously I was mistaken. Alf also tried to explain the same thing, but all in vain:-

[Quote]Gerard: read my lips: SD is not and I emphasize not a lone entity...... it sits in the context of the total ballisitics event in conjunction with a host of other parameters brought about by motion in a certain direction.[Quote]

[Quote] No matter how you cut it from what angle you approach it, or argue it, you cannot escape the fact that even your bullets at whatever velocity, at initial acceleration in barrel, in flight and at impact and penetration cannot be divorced from this ratio of it's mass to it's reference area of presentation. In each and every one of these events this ratio of mass to cross secional area comes to play.[qoute]

Some time back Sabot wrote - [Quote]For bullets of equal construction, its sectional density times velocity. However, the velocity variable is actually a curve that prevents penetration from increasing proportionately as velocity increases.[Quote] El Deguello made reference to the same thing earlier.

I am going to see if I can get pudding with some custard now and I am going to eat it slowly at 2 mpu.

Take care, I am done.
Warrior

Chris,
As long as you blow hot and cold about the same subject, you will find yourself surrounded by the confused, like I am now. Example:

Lukewarm: SD becomes more important as we move up to the big stuff, but it cannot stand on its own. We need to get the bullet into motion.
Hot: Confined to a specific caliber and the same bullet type (read construction), SD is significant. All of the above contribute to deeper penetration
Hot: SD is not outdated, Soft frangible bullets are.
Cold: the most sensible way is to look at the ratio of momentum over the bullet's frontal area,
Hot: Which one would penetrate the deepest:Before answering, consider that the bullet has more weight behind its frontal area than the round ball
Hot: The only difference between the two is their SD's
Cold: The bullet goes deeper because Mo/Xsa has been optimised by virtue of shape.
Hot: Strange that that a ratio is of more benefit that any one single parameter.
Cold: SD is not and I emphasize not a lone entity
Hot: In each and every one of these events this ratio of mass to cross secional area comes to play.

However, the velocity variable is actually a curve that prevents penetration from increasing proportionately as velocity increases. This is stagnation pressure and the relevance to the Sd discussion is......?

quote:

Take care, I am done.

Thank you, we will. But we know you are not.

Ok, lets play again but this time we'll make it a wee bit more realistic.

Lets take 2 match grade bullets where they are the same caliber but different weights. One, is a 150 grain SMK, 30 cal. Discharged from a rifle at the least velocity possible, say a 30-30, or whatever caliber you can think of.

Now, lets take the 168 SMK (obviously a higher SD), 30 cal, and stuff it over a full case of slow powder in a 30-378.

The target is a 200 pound whitetail buck at 90 yards. The aimpoint is behind the shoulder.

Which one penetrates more?

(Remember, the "pro-SD" folks are stating that ultimately, the higher the SD, the more penetration....that's the black and white of it-and I respectfully disagree).

I'm willing to bet that slow 150 will penetrate a lot futher, perhaps even pencil right on through, where that 168 is going to blow up on impact.

I'm not going to argue about the ethics of SMKs on game. The fact is, it is done, and it is common, whether we agree with it or not.

My point is, SD and SD alone, is a meaningless, worthless, totally irrelavent figure in many situations while in the field with respect to penetration.

Excellent example Doc.

Gerard you are truely confused about blowing HOT & COLD.

Read again what I said and you will notice it forms one cohesive piece accentuating the different nuances, making up my thought pattern. There can be no doubt as to what I believe. SD fits in a particular way for me - for you it fits in nowhere, and should not even exist. For me, Alf, Jeffeosso and others it is real.

Well so be it.
Warrior

quote:

Originally posted by Gerard:
Excellent example Doc.

Thank you, Thank you, no really, please no standing applause. Everybody sit, sit back down...thank you.

Warrior, I thought you said you were done.

SD IS REAL. It just doesn't amount to anything. Kind of like a wart on the bottom of a foot.

Chris,

quote:

There can be no doubt as to what I believe. SD fits in a particular way - for you it fits in nowhere and should not even exist.

Up to your old tricks again, are you? I have never denied the place of Sd (the real one, not your square bullet one) only the fact that, as a single factor, it has no bearing on penetration depth. No more no less. You actually agree with that, as does Alf, but you keep on arguing as though we disagree and that is confusing.

/

ok

HI guys I didn't think I was going to get this many replys. Looks as if I were to use a bullet from any of the major bullet maker I will be fine.
I LOVE THIS FORUM
Jerry

Jerry, glad we could help.

quote:

Originally posted by jy:
... Looks as if I were to use a bullet from any of the major bullet maker I will be fine. ...

Hey Jerry, It is possible to use the wrong Bullet Design for the task at hand. There are some Bullets that are just "better Designed" for a specific set of requirements.

If you are trying to pick a Bullet to Hunt with, it is a balancing act between a lot of variables. If you are shooting paper, it doesn't matter at all which Bullet you pick, but some are more accurate than others.

Now that you have read through all the discussion, what does SD mean to you, or are you confused?

Best of luck to you.

quote:

Originally posted by jy:
What is this Sectional Density? ......
THANKS
Jerry

Jerry,

Easy way to figure the sectional density number for a bullet:

Wt. in grains / 7000 / Diameter in Inches / Diameter in Inches again

Example: 22LR with 40 grain bullet
SD = 40 / 7000 /.223 /.223 = .115

Example: 30/06 with 180 grain bullet
SD = 180 / 7000 /.308 /.308 = .271

Example: 458 with 500 grain bullet
SD = 500 / 7000 /.458 /.458 = .341

quote:

Originally posted by Warrior:

Perhaps we should return to shooting round balls or even nigger balls just for the fun of it.

Warrior

Chris Bekker, aka Warrior:

What the hell is with the "N" word?

I thought you were banned for your racist hate speech most recently, and here you are sneaking around as "Warrior" spewing the same excrement.

Is there any redeeming social value in the above projectile description?

Moderator take note.

This clown "Bekker the Banned" is "Warrior the Wicked" and he should get a whippin' of some sort.

Warrior,
If you are not Truvelloshooter (Chris Bekker), now is the time to say so I guess.

So Bekker/Truvelloshooter/Warrior was using an old colloquial RSA name for a form of candy.

His silence confirms his identity. Time for a new handle for the troll.

I think the next user name that truvelloshooter/warrior picks ought to be "Kramer."

As in Seinfeld?

quote:

Originally posted by Gerard:
If the correct way to arrive at the BC of a bullet is: Mass /(Cd x cross sectional area) How does Sd figure in calculating BC?

Because SD is directly proportional to Mass/(cross sectional area). For the same Cd, increase SD and you increase BC.

I have to say Gerard, after all these years I'm still not sure whether you're simply quite obtuse when it comes to mathematics (as this has been explained to you many times) or if it's more of a "used car salesman"-type thing with you (your bullets have low SD, so deny SD exists or matters in any way to make $$$$, even if that means misinforming people by proclaiming 2+2=5).

After this much time, I'm starting to lean toward the latter. At least you finally took those BC figures down from your site, I thought that was a step in the right direction. I was hoping the next step would be acknowledging the reason your light, low SD bullets fell so dramatically short of your advertised super high BC's when actually measured somewhat accurately. I guess not.

Square bullets? You're arguing lack of a constant between two obviously directly proportional values to prove one doesn't exist and/or is meaningless while the other is by your own admission?

Can I get the extra super-secret undercoating along with the price-doubling extended warranty that excludes everything with that please?

You make very nice bullets, but this stuff disappoints me.

quote:

Because SD is directly proportional to Mass/(cross sectional area).

If cross sectional area is calculated the correct way and not as diameter squared. That was the implication of my post and you have taken it out of context.

quote:

Square bullets?

How else would you describe it when the "area" is calculated as diameter squared.

quote:

I have to say Gerard, after all these years I'm still not sure whether you're simply quite obtuse when it comes to mathematics

I would describe myself as mathematically challenged, especially compared to guys like you. That does not prevent me from understanding the principles involved and seeking the guidance and services of persons who can do the math and more. Which brings us to:

quote:

At least you finally took those BC figures down from your site,

I have stated this before but you probably missed it. The BC numbers on our site was a collection of different methods, done by different people and collected over a period of more than ten years. When it became apparent that a lot of the work was so badly done it bordered on fiction, I took the numbers down and we are in the process of reworking everything in a uniform manner. Some of the work done in the past was so bad, I would have fired the person responsible if they were still with us.

BC is a big thing for long range shooters and, as our HV, HP and FN bullets are hunting bullets, intended for shorter distances than the 1000yd crowd would require, I have not made it the priority you would like it to be. I apologise for that but it is being attended to. It seems that we are not the only company that has not made BC a priority in the past. It will change though, we try to improve at all levels constantly.

quote:

Can I get the extra super-secret undercoating along with the price-doubling extended warranty that excludes everything with that please?

Instead of shooting our HVs on paper, take them hunting and see how they work there. It is ultimately where they were tested and what they are intended for. It will improve your foul mood and you will get along better with all around you.

quote:

Originally posted by Gerard:
How else would you describe it when the "area" is calculated as diameter squared.

πD^2/4. Directly proportional, π/4 is but a constant--focusing on it is but a diversion when it's the variables that are in question.

As I said before, I was very impressed with the quality and accuracy of your bullets and have no doubt they'd kill anything I cared to kill with them. Just trying to keep it real.

JonA,
Please translate to English. The engineer is not available.

quote:

πD^2/4. Directly proportional, π/4 is but a constant

Wink,
You have a PM.