So when would Higher SD be a bad thing?





Serious question though

SSR

A Hunting Load should be about Balance between Accuracy, Energy available at the Point-of-Impact, Trajectory, Time of Flight and how the specific Bullet is Designed to function once it impacts.

Using a 30cal 220gr RN in a 30Carbine is waaaaaaay too much Bullet for that Cartridge, and which in response to your question would be too much Sectional Density for it's intended use. So much so that it would make the 30Carbine even less useful than it already is.

quote:

Just one thing on wind bucking - not much to do with the topic actually but sometimes a higher velocity bullet with a lower BC bucks the wind better by virtue of shorter flight duration. Just a comment.

303Guy,

Only two factors drive trajectory and wind deflection, and they are:

* the launch velocity, and
* the BC, which is derived from SD/i (form factor of the bullet)

So a higher SD can drive the BC up.

With sniping today in the 300 Win Mag, with a twist rate of 1-in-10", the heavier bullet of 190 grains is preferred over lighter bullets (lower SD bullets) such as the 168 & 175 grain bullets.

The 190 gr Sierra Matchking bullet has a really nice Ballistic Coefficient of .533
SD = .286
BC = SD/i = .286/.536 = .533

The 175 gr Sierra Matchking bullet has lower SD but a better form factor, but still a worse overall BC caused essentially by the lower SD.

BC = SD/i = .264/.523 = .505

So in the sniping world with the 300 Win Mag the higher SD bullet is still the preferred bullet.
Typically it is loaded to 2,900 to 2,950 fps.

I have not modelled the trajectory as yet nor the wind deflection, but the military has opted for the higher SD bullet and I take it that it was for a good reason.

Warrior

quote:

Originally posted by Hot Core:
A Hunting Load should be about Balance between Accuracy, Energy available at the Point-of-Impact, Trajectory, Time of Flight and how the specific Bullet is Designed to function once it impacts.

Using a 30cal 220gr RN in a 30Carbine is waaaaaaay too much Bullet for that Cartridge, and which in response to your question would be too much Sectional Density for it's intended use. So much so that it would make the 30Carbine even less useful than it already is.

No red herring answers!

Nope I know you cant use a 220 gr in a 30 carbine-you talk about balance ina load then throw that out here. thats a non answer

In a realistic,workable load when if ever can you have to much SD

quote:

Warrior

Man, this thread just went to hell!

Vapo,

Why should the thread go to hell if we post our opinions here about energy, momentum, SD and the flight of a bullet. It is rather negative to say that. Let us be positive and make the most of it by sharing ideas and experiences. Just contribute in a positive way and you do not have to agree with anyone, just express your view on the subject matter. I am sure we can learn a lot from your experience as well.

Warrior

quote:

Vapo,

Why should the thread go to hell if we post our opinions here

What?....No sense of humor?

quote:

Originally posted by Hot Core:
A Hunting Load should be about Balance between Accuracy, Energy available at the Point-of-Impact, Trajectory, Time of Flight and how the specific Bullet is Designed to function once it impacts.

Using a 30cal 220gr RN in a 30Carbine is waaaaaaay too much Bullet for that Cartridge, and which in response to your question would be too much Sectional Density for it's intended use. So much so that it would make the 30Carbine even less useful than it already is.

and good example!

quote:

Originally posted by Warrior:
303Guy,

Only two factors drive trajectory and wind deflection, and they are:

* the launch velocity, and
* the BC, which is derived from SD/i (form factor of the bullet)

So a higher SD can drive the BC up.

With sniping today in the 300 Win Mag, with a twist rate of 1-in-10", the heavier bullet of 190 grains is preferred over lighter bullets (lower SD bullets) such as the 168 & 175 grain bullets.

The 190 gr Sierra Matchking bullet has a really nice Ballistic Coefficient of .533
SD = .286
BC = SD/i = .286/.536 = .533

The 175 gr Sierra Matchking bullet has lower SD but a better form factor, but still a worse overall BC caused essentially by the lower SD.

BC = SD/i = .264/.523 = .505

So in the sniping world with the 300 Win Mag the higher SD bullet is still the preferred bullet.
Typically it is loaded to 2,900 to 2,950 fps.

I have not modelled the trajectory as yet nor the wind deflection, but the military has opted for the higher SD bullet and I take it that it was for a good reason.

Warrior

Warrior is exactly right! <----rc hiding from Vapo!

I first developed a load for my .300 WM target rifle for LR steel shooting with a 168 A-Max. It's really accurate but only a BC of .454 but at high velocity around 3200 fps. I changed over to the 208 A-Max at around 2875 fps and a big BC of .654.

The Higher velocity of the 168 doesn't overcome wind drift. The 208 shoots so much better (ie. easier to make long range hits because of its greater ability to buck the wind)

Obviously the heavier bullet is longer which increases its sectional density.

quote:

Originally posted by rcamuglia:

quote:

Originally posted by Hot Core:
A Hunting Load should be about Balance between Accuracy, Energy available at the Point-of-Impact, Trajectory, Time of Flight and how the specific Bullet is Designed to function once it impacts.

Using a 30cal 220gr RN in a 30Carbine is waaaaaaay too much Bullet for that Cartridge, and which in response to your question would be too much Sectional Density for it's intended use. So much so that it would make the 30Carbine even less useful than it already is.

and good example!

quote:

Originally posted by Warrior:
303Guy,

Only two factors drive trajectory and wind deflection, and they are:

* the launch velocity, and
* the BC, which is derived from SD/i (form factor of the bullet)

So a higher SD can drive the BC up.

With sniping today in the 300 Win Mag, with a twist rate of 1-in-10", the heavier bullet of 190 grains is preferred over lighter bullets (lower SD bullets) such as the 168 & 175 grain bullets.

The 190 gr Sierra Matchking bullet has a really nice Ballistic Coefficient of .533
SD = .286
BC = SD/i = .286/.536 = .533

The 175 gr Sierra Matchking bullet has lower SD but a better form factor, but still a worse overall BC caused essentially by the lower SD.

BC = SD/i = .264/.523 = .505

So in the sniping world with the 300 Win Mag the higher SD bullet is still the preferred bullet.
Typically it is loaded to 2,900 to 2,950 fps.

I have not modelled the trajectory as yet nor the wind deflection, but the military has opted for the higher SD bullet and I take it that it was for a good reason.

Warrior

Warrior is exactly right! <----rc hiding from Vapo!

I first developed a load for my .300 WM target rifle for LR steel shooting with a 168 A-Max. It's really accurate but only a BC of .454 but at high velocity around 3200 fps. I changed over to the 208 A-Max at around 2875 fps and a big BC of .654.

The Higher velocity of the 168 doesn't overcome wind drift. The 208 shoots so much better (ie. easier to make long range hits because of its greater ability to buck the wind)

Obviously the heavier bullet is longer which increases its sectional density.

And SD is an intergal part of the BC
The farther the range the more important BC becomes in bucking wind

Vapodog,
Last time I looked the thread was about momentum and energy. It is a given that Warrior cannot tell the difference between momentum, energy and SD.

So I took his post to the SD thread and fixed it along the way. I had to fix it because only Warrior could think that a form factor of .523 is better than a form factor of .536 and then build a statement on it "proving" how right he is, winding up all wrong.

You have to check everything he says and every calculation he makes.

quote:

Warrior posted:
The 190 gr Sierra Matchking bullet has a really nice Ballistic Coefficient of .533
SD = .286
BC = SD/i = .286/.536 = .533

The 175 gr Sierra Matchking bullet has lower SD but a better form factor, but still a worse overall BC caused essentially by the lower SD.

BC = SD/i = .264/.523 = .505

quote:

Originally posted by Gerard:
Vapodog,
Last time I looked the thread was about momentum and energy.

Actually it has nothing to do with that.....it has a lot more to do with hunting elk with a .223!!!

quote:

Originally posted by vapodog:

quote:

Originally posted by Gerard:
Vapodog,
Last time I looked the thread was about momentum and energy.

Actually it has nothing to do with that.....it has a lot more to do with hunting elk with a .223!!!

quote:

It is a given that Warrior cannot tell the difference between momentum, energy and SD. So I took his post to the SD thread and fixed it along the way. I had to fix it because only Warrior could think that a form factor of .523 is better than a form factor of .536 and then build a statement on it "proving" how right he is, winding up all wrong.

Gerard,

Yes I do believe that a lower numeric value for a form factor is better, since we are dividing with it in the equation of BC = SD/i. By dividing with a lower figure (or fraction) we drive the BC value up, not so?

If you still have any doubts about the logic, go look on page 114 of the Speer Reloading Manual No. 12.
There you will see an example of 4 different .308 150 grain Speer bullets:

i = .843 iro a Flat Point bullet
i = .741 iro a Grand Slam bullet
i = .581 iro a Spitzer bullet
i = .534 iro a Spitzer BT bullet

Clearly the most aerodynamically shaped bullet, the Sptitzer BT, has the lowest numeric value, but it is the most efficient of the lot or sleekest if you will that will encounter the least drag in the air.

So it then appears that I am actually right Gerard, and that I am not the only one that thinks this way.
So there is nothing wrong with what I posted and why the military has gone that way.

You should also note that I confined my self to one brand of bullet that the military is using and not different brands that have different shapes that could alter the final BC as we all well know. And yes we can still get a high BC on a light but very sleek bullet with a low NUMERIC VALUE for a form factor.

Warrior

We could also consider 3 bullets in .308 caliber with identical cylindrical shape with a form factor of 1.0 so as to simplify the comparison:

150 grains - SD = .226
175 grains - SD = .264
190 grains - SD = .286

BC = SD/i

Since i=1, SD will drive the value of BC up.
And so, SD = BC



Warrior

Thanks for the informative responses to my comment. I knew there was a 'break even' point and have given up on the iea of lighter and faster in my rifles for the simple reason that there is no actual gain in trajectory at longer ranges and certainly there is a loss in energy and momentum at the ranges where I think one needs it most (with lighter and faster bullets that is).

For what it is worth, I find this thread and the topic very interesting. After all, I do have to make choices - 150 versus 180gr's for the 303 Brit and 180gr paper patched cast versus 208gr paper patched cast in another 303 Brit or two!

Highest .300 Caliber BC bullet per the updated Oehler ballistics program:

175 gr Berger-----.537
190 gr Berger-----.583
210 gr Berger-----.640

200 gr Sierra MK--.565
220 gr Sierra MK--.629
240 gr Sierra MK--.711

Warrior

Did you ever walk right into that one. You did not see it coming, did you? I should have placed bets again. You have delivered absolute proof that you do not understand BC, SD or any of the single concepts that make up the ballistics whole.

Therein lies your problem: You are incapable of dealing with multiple concepts, being only capable of addressing single factors.

If someone is interested in what the reason for Warrior's folly is here, and there is no shame if you do not know and want to know, drop me an email on gerard(at)wol.co.za. Warrior you need not bother, I have no desire to educate the unteachable.

The hilarity comes when you, Warrior, refuse to debate, answer questions, pretend you know, and sprout GoogleFu in the belief that you know it all. Repetition of wrong does not make wrong right and endless repetition does not make facts fit where they do not.

Erm, Warrior.

If the form of the bullet changes then the number given as 1 in your B.C. equation is invalid.

I think B.C. is calculated relative to a standardised Krupps round nosed projectile of one pound weight and something like an inch in diameter ( I can't remember and can't look it up here ).

It follows that the equation you quote above would be valid for comparing bullets of the same nose and tail profile but with differing shank lengths as a means of varying weight.

S.D. is used in that equation as a convenient ratio, and therefore composite, of length, weight diameter.

As to the others, are you lot seriously trying to model bullet behaviour on game with less than half a dozen variables?

Seems odd to me lads how do other branches of object collision similation for the number of factors and variables they take into account.

This is a hiding to nothing, at best any equation come up with can only be checked for validty by comparing it with what we an experienced hunter knows works or doesn't work!

[quote from Gerard]The hilarity comes when you, Warrior, refuse to debate, answer questions, pretend you know, and sprout GoogleFu in the belief that you know it all. Repetition of wrong does not make wrong right and endless repetition does not make facts fit where they do not.[/quote]

Seems to me a bit hypocritical on your part as those are the same tactics that you have used to not respond to my question in my last post to you!

465H&H

quote:

After all, I do have to make choices - 150 versus 180gr's for the 303 Brit

303Guy,

The decision you have to make, as contemplated above, we all have to make daily, and it is simply a decision based on SD, even if we would like to deny it. The moment when you pick one bullet weight over the other, you have discriminated against the other for whatever the reason might be, and that decision rests intrinsically on SD.

SD is not absolute and cannot be used as such, as I have stated many times, as we should not make non-sensical comparisons of cross-caliber, different designs and bullet material. Now the pundits that attack SD normally just do that to prop up their arguments. We must be clear that the SD decision is made in respect of a particular caliber. Who in his right mind will argue that a 175 gr 7 mm bullet with an SD of .310 is superior over a 500 gr .510" bullet with a SD of .275 used in a 500 Jeff.

SD has its rightful place as one of the building blocks and must be seen in context with the other equally important building blocks so as to give us a result greater than the sum of its parts, and that we call the synergistic effect of 1 plus one is equal to 3.

If SD was a non-event the military would have opted for the lightest bullet at the fastest velocity rather than the 190 grain bullet for sniping, but they did not, and with good reason. There is a host of 150 and 155 grain 'Palma' bullets that can be used in the 300 Win Mag, but they were not preferred by the snipers, Seals and USMC soldiers.

And that's the way it is.

Warrior

Good grief!!! All of this claptrap!!!
Where's a REAL ballistics Engineer when we need him?

Bear in Fairbanks

To try to tie all this back to the thread topic, I thought I'd use this Energy/Momentum Taylor's Knock Out Calculator and JBM Ballistics with the givens I posted about my .300 WM target gun.

168 gr A-Max at 3200 fps
SD = .253
BC = .475

Energy = 3859 ft/lb at the muzzle, 1816 at 500

Momentum = 2.392 lb/sec at muzzle, 1.646 at 500

TKO value = 23

Wind Drift at 1000 = 84.7"

Drop at 1000 = 268.8"

208 gr A-Max at 2875 fps
SD = .313
BC = .648

Energy = 3816 ft/lb at the muzzle, 2215 at 500

Momentum = 2.66 lb/sec at muzzle, 2.054 at 500

TKO value = 25

Wind Drift at 1000 = 62.6"

Drop at 1000 = 278"


Energy/TKO/Momentum at the muzzle is similar between the two
The lighter/smaller SD and BC bullet loses energy and momentum faster
The Heavier/Bigger SD and BC bullet retains more energy and momentum at longer ranges
The bullets have similar drop at longer ranges
The Heavier/Bigger SD and BC bullet has much less wind drift allowing more error for hits
Energy/TKO/Momentum of the Bigger BC/SD bullet at Longer Ranges is more appealing for hunting
The bullet with larger SD/BC is ballistically superior in summary.


If one applies this information in general to hunting, it validates the OGW and TKO formulas which always show preference to heavy bullets for game.

I am starting to believe the preponderance of the data also shows a preference of Momentum over Energy when choosing caliber/load for all of the reasons above:

Ballistic superiority for greater accuracy, Momentum driving penetration for better killing ability

quote:

Originally posted by rcamuglia:
To try to tie all this back to the thread topic, I thought I'd use this Energy/Momentum Taylor's Knock Out Calculator and JBM Ballistics with the givens I posted about my .300 WM target gun.

168 gr A-Max at 3200 fps
SD = .253
BC = .475

Energy = 3859 ft/lb at the muzzle, 1816 at 500

Momentum = 2.392 lb/sec at muzzle, 1.646 at 500

TKO value = 23

Wind Drift at 1000 = 84.7"

Drop at 1000 = 268.8"

208 gr A-Max at 2875 fps
SD = .313
BC = .648

Energy = 3816 ft/lb at the muzzle, 2215 at 500

Momentum = 2.66 lb/sec at muzzle, 2.054 at 500

TKO value = 25

Wind Drift at 1000 = 62.6"

Drop at 1000 = 278"


Energy/TKO/Momentum at the muzzle is similar between the two
The lighter/smaller SD and BC bullet loses energy and momentum faster
The Heavier/Bigger SD and BC bullet retains more energy and momentum at longer ranges
The bullets have similar drop at longer ranges
The Heavier/Bigger SD and BC bullet has much less wind drift allowing more error for hits
Energy/TKO/Momentum of the Bigger BC/SD bullet at Longer Ranges is more appealing for hunting
The bullet with larger SD/BC is ballistically superior in summary.


If one applies this information in general to hunting, it validates the OGW and TKO formulas which always show preference to heavy bullets for game.

I am starting to believe the preponderance of the data also shows a preference of Momentum over Energy when choosing caliber/load for all of the reasons above:

Ballistic superiority for greater accuracy, Momentum driving penetration for better killing ability

There ya go!!! After 4 pages of baloney, one way or the other, a succinct description. Sums it up precisely. What a number of us wrote in previous pages that few paid any attention to.

Bear in Fairbanks

Not to stir the pot



but the effect on game would depend on the game wouldnt it? Praire dogs ,coyotes , antelope, I dont want penetration but explosive enery dump.

Just sayin



SSR

quote:

Originally posted by rcamuglia:

quote:

Originally posted by Red C:
...Also, I believe, in the real world of hunting, one might be willing to sacrifice a little momentum in favor of a flatter trajectory that some smaller, faster bullets afford (as long as you still have adequate killing power).

Only when taking into consideration the Game being shot.

Size of game's kill area

Toughness of game's skin, bone

Average range of the shot

Location of vitals

No matter the trajectory of a projectile of a given cartridge, one can still put the bullet accurately on target by any number of methods; dialing data, holding over with a ballistic reticle. It wouldn't make sense to shoot a 22-250 at Oryx simply because it is flatter shooting and will increase your ability to make an accurate shot placement at longer ranges (The .223 for deer contingent will argue with that ). Now choosing the 7mm RUM for the task makes sense. Same trajectory as the 22-250 with lots of energy/momentum because of a heavy bullet going really fast.

If a proponent of small calibers for big game does any type of long range target shooting, he will soon see through experience the advantage of shooting heavy bullets for game as well.

Big Ballistic Coefficients for bucking the wind

Higher Sectional Density

Heavier projectile that will have more energy/momentum at the target

I watch lots of different bullets hit steel plates. The big ones make them move a lot even at 1000 yards. At 200 yards, they make them spin like Olga Corbitt on the High Bar at the Olympics.

The smaller caliber, lighter bullets sometimes make calling a hit or miss difficult.

The OGW formula and TKO formula do a pretty good job helping with cartridge selection and I believe you won't be making a mistake by using either.

Hey Cross!

Just like I said on page 3

quote:

There ya go!!! After 4 pages of baloney, one way or the other, a succinct description. Sums it up precisely. What a number of us wrote in previous pages that few paid any attention to.

Bear in Fairbanks

Please show us the ones that were ignored that say what mine does

RC,

Missed that, man apologies



SSR

No need for that!

Guys, why are we complaining so?
We all know how the internet is by now, don't we?
Someone can start a thread with the title "How much is 3+3?" There will probably be two, maybe three pages of responses. None of them have read what was posted previously, but they just had to get their answer in. Trouble is, some might say "5" and some others say "7". Then the ones who say "6" will debate with those who say "7" and "5" and vice versa. Some who say "7" and "5" will make a strong case that two odd numbers added together couldn't possibly result in an even number. Flaming begins, feathers are ruffled, insults are exchanged. A number of posters enter the thread just to say "Who cares? You're all stupid!" Moderators may even be notified because of heated exchanges. Then memberships might get revoked. Some well-intended may come in with diplomacy to help ease the dispute. "There probably is no ready answer. It's just all a matter of perspective." Then that person gets flamed. He/she flames back. After 16 pages, nothing is settled. The original poster leaves the board in frustration, uses his calculator, and finds out that the correct answer is 6.

It's ugly, I tell you! Ugly!

Of course, I'm exaggerating, but I think you see the point: It's the internet, for God's sake! It's the nature of the beast!

I don't know who's complaining.

I was just letting Cross know that he didn't need to apologize to me for anything.

I've thoroughly enjoyed this topic and thank Vapo for starting it. I've learned from it.

Grins

Glenn,

I reckon you, RC, and I hope myself are amongst the good guys. Have a little fun, exchange some ideas, dont let some of the pissin matches get to you.

SSR

quote:

Originally posted by rcamuglia:
I don't know who's complaining.

I was just letting Cross know that he didn't need to apologize to me for anything.

I've thoroughly enjoyed this topic and thank Vapo for starting it. I've learned from it.

RC, it wasn't you I was talking about. I was referring to this:

quote:

There ya go!!! After 4 pages of baloney, one way or the other, a succinct description. Sums it up precisely. What a number of us wrote in previous pages that few paid any attention to.

And this:

quote:

Good grief!!! All of this claptrap!!!
Where's a REAL ballistics Engineer when we need him?

quote:

Grins

Glenn,

I reckon you, RC, and I hope myself are amongst the good guys. Have a little fun, exchange some ideas, dont let some of the pissin matches get to you.

Thanks, Cross.
I guess one of my faults has always been oversensitivity. This probably doesn't make for a very good internet forum member, but I still keep coming back for more punishment.

Heck Glenn

I just flipped out on the SD tread---Read it and weep



SSR

quote:

I just flipped out on the SD tread---Read it and weep

I'd say it was appropriate!

quote:

Originally posted by Cross L:
Heck Glenn

I just flipped out on the SD tread---Read it and weep



SSR

I saw it, Cross! You da man!


I tried sweet talk on the usual suspects, but to no avail. I see that it's now time for me to once again invoke St. Ignora, patron saint of internet forums.

quote:

Originally posted by someoldguy:

quote:

Originally posted by Cross L:
Heck Glenn

I just flipped out on the SD tread---Read it and weep



SSR

I saw it, Cross! You da man!


I tried sweet talk on the usual suspects, but to no avail. I see that it's now time for me to once again invoke St. Ignora, patron saint of internet forums.

SOG

being catholic St Ignora sounds female to me. The a-ending in latin gen denotes the femanin gender so that would be PATRONESS-


Sorry its been a looooong day and I couldnt resist

SSR

quote:

SOG

being catholic St Ignora sounds female to me. The a-ending in latin gen denotes the femanin gender so that would be PATRONESS-


Sorry its been a looooong day and I couldnt resist

I actually think she's Jewish. Her day job is as a bitchy judge in a small claims court.

you da man

SSR

There has been an underlying sense of sensibility all along. Putting the question of mass versus velocity into perspective is hard to do. Nice heavy and not so fast works well in some instances but that faster and flatter would have been handy sometimes. Then I go out hunting with my faster and flatter 150gr 303 Brit bullets and get bleading in the rump from shoulder shots! Meat damage too. Not to mension bullet failure on entry with a close up raking rib shot. Sure, the antelope died right there but the skin was ruined. So I switched to the heavier 180's and one day found myself unable to get the trajectory right for a long range small critter target. I got it but hit a little low. Now I find the 180's require careful shot placement on feral goat if I want to anchor them on the spot because they are not an explosive bullet at those velocities. On one occasion I shot a pig in the darkness of a half moon and thought I was aiming at his right shoulder but actually hit him in his left shoulder. That 174 grainer broke his shoulder, split his heat wide open, burst his liver and exited above his left back leg. Perfect bullet performance and DRT. But I realized the possibility existed to do 'Texas' heart shots on pigs in the dark and that the high SD bullets were the only way to go.

Just saying why this has been an interesting thread.

Plus it's been interesting to learn of the knowledge, thought and unstanding of so many folks on this and other threads.

quote:

Plus it's been interesting to learn of the knowledge, thought and unstanding of so many folks on this and other topics.

I agree. I only have thought, not much knowledge or understanding. Some of my thoughts might be wrong, too.

I like my knowledge and understanding in bite sized pieces laid out in a logical, easy-to-read, practical fashion. I think this can be done so that we unlettered masses can follow to some degree.
After all, this is rocket science we're talking about, not brain surgery.