Sectional density and overall weight

[Treeman]

I hope I can make this question clear, I am not asking about SD and deformed bullets and does it matter or not.
What I want to know, within realist and usable parameters, the following.

Will a heavier bullet penetrate deeper than a lighter bullet with a greater SD even if the heavier bullet is larger in caliber.
So we take a .270 Win 150gr with a SD of about 280 bullet and shoot it into a elephants rump it travels 70 cm.
If we shot an 416 Cal bullet at the same speed that weighed 250 gr but only had a SD of 190 due to caliber size, would the heavier bullet travel deeper just because it was that much heavier.

Would a 165 gr, .308 .248 SD bullet at 2500 fps outreach an 6.5 140 gr bullet with .287 SD at 2500fps.

Does total mass beat SD ?

[Treeman]

is there no one that has insight on this matter ?
I have googled myself "stukkent" , everything is caliber only, no cross the board info. 

[BBCT]

I think there are too many other variables to be able to make a confident call on this one.

[Ds J]

Speed plays a role. The 45-70 is said to penetrate better at lower speed than other .45 bullets at higher speed. It has to do with the target's resistance.

[oafpatroll]

I think there are too many other variables to be able to make a confident call on this one.

My gut says this is the answer. It can't be single factor thing. SD is 'just' a ratio. You could have an artillery shell with a lower SD than a rifle bullet with a super high one and at the same velocity it would still penetrate your elephant/s better.

[Treeman]

Ok - lets put it this way,the average heavy for caliber for say .270 @ 150 gr - .308 @ 180 gr- .385 @ 300 gr and say a .458 @ 400 gr all shot at their functional speeds.
Would the .458 and .375 end deeper just because there was more weight in motion, or would the .270 win because SD is so high?
Would the pure mass of a 400 gr bullet (2.5 x that of the .270) trump the good SD of the .270 because it only has 150 gr to work with.
My thought is that it surely must, because the .375 shoots through elephant's or reach's 1 - 2 m into it (I think)
The . 270 even shooting a 170 gr bullet with a Sd  far far above the .375 bullet will not do that, or will it ?
Is it called momentum, weight in motion ? Does momentum count ?Will that cause the 458 to get deeper, even if its sd is less than the .270, the .270 just does not carry enough whatasaname.

[Treeman]

I think there are too many other variables to be able to make a confident call on this one.

My gut says this is the answer. It can't be single factor thing. SD is 'just' a ratio. You could have an artillery shell with a lower SD than a rifle bullet with a super high one and at the same velocity it would still penetrate your elephant/s better.

**********************
Yes, this is what I am trying to pose or question but lacking transmitting ability. Perhaps "is heavier just better, every time, every way, just deeper penetrating"

I just bought a 7x57, and I was disappointed to find that the .270 trumps it in almost every comparable way. I somehow thought that the 7x57 was this wonder penetrating caliber, but if Sd is used, the .270 is better, so I got to wondering if the 7x57 with same SD as .270 would penetrate deeper just because the same SD bullet is heavier and therefore regardless of the numbers it would travel deeper. 

[Ds J]

Penetration is the ability to overcome resistance as effective as possible.

It would mean something similar to the BC whilst travelling through air, but with more variables.

Any engineers on board?

[DaavG]

I think there are too many other variables to be able to make a confident call on this one.

My gut says this is the answer. It can't be single factor thing. SD is 'just' a ratio. You could have an artillery shell with a lower SD than a rifle bullet with a super high one and at the same velocity it would still penetrate your elephant/s better.

**********************
Yes, this is what I am trying to pose or question but lacking transmitting ability. Perhaps "is heavier just better, every time, every way, just deeper penetrating"

I just bought a 7x57, and I was disappointed to find that the .270 trumps it in almost every comparable way. I somehow thought that the 7x57 was this wonder penetrating caliber, but if Sd is used, the .270 is better, so I got to wondering if the 7x57 with same SD as .270 would penetrate deeper just because the same SD bullet is heavier and therefore regardless of the numbers it would travel deeper. 

Why not wet pack test the 2 calibres and see the results physically? Not ideal medium but sure as hell better than any formula or equation surely.

[Treeman]

interesting article on the subject.
Some notes: Double your weight and you double your energy, but double velocity = quadruple energy. It seems that velocity beats mass.
 158 gr bullet/100 gr 9 mm bullet at respective near max velocity for bullet weight.
401 J - 296 ftlb / 558 J - 412 ftlb, thats 25% more energy for a 30 mass reduction and about 40 increase in velocity (915 fps/1360 fps)
https://webpath.med.utah.edu/TUTORIAL/GUNS/GUNBLST.html#2

[Treeman]

So when Cody and I are on our bellies crawling through the thick stuff, it would be better to have 100 gr bullets than 158 gr bullets ?
When facing bushpig and warthog at close quarters, you want that bullet to travel as far as possible through target, often the shot is without choice from rear to stop a wounded animal from furthering away.
The above takes me back to Impala bullets - doubt they can be beat for sub sonic penetration ?

[janfred]

Problem there is that the faster the bullets go, the more inertia the impacted flesh have. This causes larger expansion on the bullet and either bullet failure or insufficient penetration with plenty meat damage.

[Ds J]

It seems that tests give different results, depending on things like bullet type (lead vs mono vs cup&core vs FMJ), bullet speed, penetrated medium etc.

The only way to know for sure is to shoot one type of bullet at several speeds. Example: 139gr Hornady Interlock in a 7-08, 7x57, 7x64 and 7mm Rem Mag.

Then repeat the same test with a mono bullet, and yet again with FMJ bullet.  The test would probably only partially possible with lead bullets due to the speed limit on lead.

Another possible test would be to get different bullets for one calibre, with equal weight, and shoot them at the same speed.

[Ds J]

It depends much on bullet weight, design and speed as well as the target medium.

With my 357 Mag snubbie I experienced following vs a 9mm P:

• The 9mm with FMJ range rounds (124gr) penetrated better than 158gr Hornady XTP +P loads at 5m. We fired into conveyor belts; the 9mm penetrated the first belt and into the second; the 357 barely passed the first belt. Both bullets were not bent out of shape by much.
• The 9mm with FMJ range rounds (124gr) knocked over hinged falling plates at 7m-10m; the 357 with 158gr SWC hit with enough force to knock them down and they sprang back up.

The 45-70 has enough penetration to shoot through (kill) any African game; however hunters opt for the faster 458 calibres because of the "wallop" factor because the 45-70 (apparently) does not stop a charge.

The 357 Mag usually shot 158gr bullets until the FBI figured out that a 125gr bullet gives better performance for police work.

Regarding your 9mm question: you need both penetration and wallop. I would test a solid 9mm flat point if available.

[Ds J]

From https://www.shootersforum.com/threads/penetration-the-45-70-458-magnums.9085/page-2?nested_view=1&sortby=oldest

Regarding medium;
At the Midwest Big Bore Seminar, we use two seperate stacks of wet pack for the penetration tests. They are 8 feet in length. We cronograph the shooters bullet/load and send him to the first stack which contains wet soaked newspaper. After firing we leaf through the paper stack to determine the wound cavity and bullet path. Mark where the bullet stops recover the bullet. We then assess the condition of the bullet and measure the distance traveled. It is the homogenous medium.
The shooter moves to the next stack and it is set up in a similar manner with the addition of a beef femur/ forleg bone placed in the stack at the 4" mark. This is to simulate the approximate position of most larger animals. After firing we make sure the bullet struck the bone, leaf through the stack to determine the wound channel and bullet path. We mark where the bullet stops, recover the bullet. We then asses the condition of the bullet and measure the distance traveled after the bone.
The addition of the bone will really change the condition of the bullet. It is really tough on bullets.
This gives us an idea of how the bullet will under some really extreme impacts.

During this shoot, we test deforming and non-deforming projectiles. As one might expect, bullets of the expanding variety perform all over the spectrum based on their construction and impact velocity.
There are so many variables in this field alone it will make your head swim. A manufacturer may have several differing styles of bullets construction. Over time you will see what each design acts like and certain velocities. Although some bullets designs will fail to penetrate as far or hold together as well as another manufacturer or design, it doesn't mean it's junk. It then falls to the shooter to select the appropriate application for the bullet. If you thought your bullet was an elk bullet and it turns out that it may be better suited for deer, now you know where to use it. I personally prefer a bullet that leans heavily to the tough side when shopping for expanding bullets. And as I get older, I'm less enamored with super pointy bullets. I guess my bullets are starting to look like me, bald and round on top and fatter in the middle.

Solids on the other hand are another story.
Lets start with the hardcast lead bullet. Alloy strength, velocity and nose design are all critical to the performance of the bullet. Even really tough lead is not very strong when compared to copper and brass. you can increase velocity until the impact overcomes the strength of the alloy and your bullet fails. I've shot some of Mr Garret's 45-70 stuff, and it is a real tough alloy. He has done his homework and offers a fine product.
So what happens to lead solids? An example is the 500 Linebaugh pistol with 435 gn WFN bullet.
1,000 fps--- wet paper penetration 28"
1,200 fps--- wet paper penetration 31"
It's worthy to note that with a 20% increase in velocity the penetration was increased by 3" or roughly 10%
Use the same bullet in a 50 Alaskan an run it up to 1,700 feet per second and it will overcome the alloy strength and blow the noes off. this reduction of mass yields less penetration. ( it might be noteworty, we shot some 480 grain WFN at 1,700 out of the 50 Alaskan in the plain paper, The bullets lost their noses and the recovered weight was 420 grains. The penetration was 24" I know it's not apples to apples, but noteworthy)

"AHA!" YOU SAY, "The reduction of mass is the cause of the penetration reduction. You still need to prove the more velocity equals less penetration with a non deforming solid"

First we need to realize that Mr Gates Slugs are not going fast enough to overcome the alloy strength. Therefore there is no reduction of mass with his slugs in wet paper. However, his slugs have a considerably larger meplat. The new Dixie's feature what I would term as a short dome wadcutter with meplat. It pushes or displaces with nearly the full diameter of the bullet. Hence his bullet is also recieving nearly that full area in material stagnation.
Others will note that the Dixie "doesn't have a high sectional density, like a 458". Well, well it has better sectional density than any 12 full caliber slug on the market (.196 compared to a 250gn Keith 44mag at .194), and better that some sabots. Mr Gates Dixie slugs are very impressive. I believe that he has a great thing going and has the description of their intended purpose, accurate to the letter. I believe they are a worthy purchase.

Let's eliminate the lead strength problem and use brass flatnose solids. Now we're talkin'. I've shot some of these. They are scary as to how far they will go. I've got some 338 Win Mag that are Barnes round noses turned to provide a 65% meplat. I honestly don't know how much wet paper it will take to stop them. The first time we did the penetration tests we used about 4 feet of paper, they would blow through that and head across the Illinois prairie. After 55" of paper 3" red fir 2x12 and 2"more paper we finally caught them. (I've added alot of paper to the stack and am now shooting an 8' stack of wet paper. using these solids they will go through 4" paper a beef femur and an adittional 72", yes 6 feet of paper) I'm sure you will say "See 2,400 fps penetrates better than the other bullets you mentioned" It does penetrate farther. but it has .08972 square inches of total frontal surface area, and .03801 square inches of surface area on the actual meplat. Compare that to the Dixie at .4173 square inches total. It displaces alot less material.

So, can I prove that this always happens? Can I prove at what velocity that this takes place? Can I prove it with new data that will be accepted? I'LL TRY!

Since you may realize that I dont wan't to be shooting through 10, 12, or 15 feet of paper with a high sectional density, high mass bullet. ( lots of work!!!) I think we can prove this with a lighter bullet. ( less mass ) Say, in the 458 dia.( less paper killed, less field dressing to do)
I'll do a bullet in the 350 grain range and work the loads and see what velocity things start to go south. I'll start with the 45-70 and since I'm sure we'll need more speed, I may have to rechamber the old Ruger No3 to 460 Weatherby. I think it'll work without having to change the ejector. If not I'll use a cleaning rod ejector.

The same bullet will be used throughout. Weight, mepalt, diamater. The only thing changed will be speed.
This will give us DATA that is form testing especially for this forum and I'll post my results here.
Fair Enough?