Where do you stand on Sectional Density?

[NoStepOnSnek]

I heard on a podcast the other day that sectional density doesn’t matter as much with modern bullets. In my mind a 300 gr 458 Win Mag should be substantially more effective than a 300 gr 375H&H, but SD says otherwise. However, the SD concept was developed during WW1 from what I understand, with no updates to account for improved bullets. How do yall feel about it?

 

[375Fox]

I’m not sure any of your answers are really correct. Sectional density isn’t a good way to compare different brands of bullets because different designs function differently. It is another way to compare different bullet weights of the same brand lead core bullet. I think I’d lean towards it matters but not as much as bullet design. Once a bullet mushrooms it has a very different sectional density. For monolithic bullets, I don’t think it has the same importance depending on the bullet.

I would not consider using a 300 gr 458 bullet over a 300 gr 375 bullet though. I’d expect very little penetration from a 300 gr lead core 458 after it mushroomed on dangerous game.

 

[BryceM]

Well, "good bullet" often means one with a high sectional density..... so your questions make a bit of a circular argument.

If you're comparing solids, the 300 gr .375 will almost surely penetrate better than a 300 gr .458 bullet. For most purposes, the .375 is probably better in this situation. A proper 500 gr solid in .458 is probably better than either of the 300 gr bullets if we're talking about a situation calling for penetration.

If you're comparing other types of bullets, the construction of the bullet matters more, but again, SD is one of the characteristics that makes good bullets good.

 

[Mark458]

I'm definitely on the side of sectional density does matter. Bullets are definitely better today than they used to be, but higher sectional density will still penetrate better when all other factors being equal. Heavier in the same caliber will penetrate better than a lighter version of the same bullet.

When you try comparing different calibers as you did then you are going to get very different results depending on multiple factors.

When it comes to dangerous game I believe going with higher sectional density will rarely let you down

 

[IvW]

SD is tops for DG ideal top performing SD is around .330 or slightly more

 

[DaddyFlip]

We beat this horse to death many moons ago. Sectional density is merely a calculation, not a metric; it is, however, made up of two metrics that do matter... diameter and weight. Sectional density doesn't care about the shape, construction, material, color or brand of the projectile. It is a boring mathematical ratio that doesn't matter. For a given bullet within a caliber, heavier penetrates more. Across calibers, smaller diameters of the same weight penetrate more. Maybe I should say it a different way; it's not that it doesn't matter, it's that it's not a factor. Diameter and weight are the factors.

SD is good for marketing bullets, though; especially smaller diameter ones.

 

[DaddyFlip]

@IvW gave me an idea how to better illustrate why SD doesn't matter (is not a factor). Consider the following Hornady projectiles - Same "ideal top performing SD for DG of .330"; which one are you choosing for your buffalo hunt? You didn't pick the 416 because of SD, you picked it for (1) energy; (2) diameter; (3) weight. SD never crossed your mind. Even if the 30cal bullet was the same DGX Bonded construction, you wouldn't choose it for your buff hunt because the SD was .330. Even if it were legal, you never considered your 300 H&H for buffalo. SD doesn't matter.

Now if you're choosing between 300-350-400-450 grain bullets for the 416, they will all do the job on buffalo. The heavier the weight, the higher the SD, but that's only a consequence of the weight increasing, not some magical significance of SD. (By the way, every 416 bullet of equal weight has the same SD, regardless of any other metric, making SD even less significant when considering which brand and type of bullet you want to use.)

 

[318AE]

375Fox summed it up well.

The roughly .3 sectional density rule of thumb for dangerous game dates back to when cup and core bullets were common. Their retained weight was poor and erratic by today’s standard, and additional bullet weight or sectional density was one way to compensate for poor retained weight, to get adequate penetration.

Monolithics have essentially 100% retained weight and often need a certain minimum velocity to open well, so they do better at lower sectional densities.

So does sectional density matter? Of course. I don’t want a .1 SD in any bullet - there is an appropriate bullet weight (and SD) for any given bullet diameter and construction.

 

[Mark458]

Sectional density is merely an indicator of momentum which translates to penetration. If you're hunting dangerous game and you want maximum penetration then you are going to choose the heaviest bullets within the chosen caliber which in turn is going to have the highest sectional density.

The chart shown above shows the same sectional density of two different calibers. Obviously the larger caliber is going to inflict more damage to the animal. A better choice of charts would compare a range of calibers that you would choose from to hunt dangerous game. 375 H&H to let's say 505 Gibbs to keep it within reasonable choices.

A few examples of these are

Caliber. Weight. SD

.375 350. .356
.416. 430. .355
.458. 550 .375
.505. 600. .330

Notice that these are all heavy for caliber options.

You can see that the 375 caliber at 350 grains has a SD significantly higher than the 505 Gibbs. It may very well penetrate better than the Gibbs. Is there anyone on this forum that is willing to argue that the 375 is going to do more damage than the Gibbs given they are utilizing the same bullet (let's say a Swift A Frame)

The one that stood out to me was the 458. That has been my caliber of choice for some time now. It has the best SD and is a large diameter. The best possible penetration while inflicting a large wound channel.

Let the debate continue.

 

[Schüler Jumbo]

SD matters with a cup & core bullet but not as much with monometal. A “good bullet” can be either a cup & core or monometal.

 

[Mark458]

SD matters with a cup & core bullet but not as much with monometal. A “good bullet” can be either a cup & core or monometal.

Light for caliber bullets, even monometal, can be an issue with penetration. I've talked with a few PH'S that have had clients hunt buffalo with 250 or 270 grain bullets with their 375's and have had problems with penetration when hitting the shoulder bone. I'm all cases they ended up getting the buffalo, but tracking and follow up work was required.

 

[deewayne2003]

I killed 5 water buffalo, scrub bull, brumby and several pigs with a .404J using 350gr Woodleigh RNSN with an SD of .281 which is just slightly better than an ashtray.

I had my doubts at first but they quickly vanished when I saw how effective they were and recovered several that were perfectly mushroomed.

Personally I prefer heavy for caliber bullets, so if my .404J ever gets finished I’ve got a supply of 450gr RNSN with an SD of .361 which should be quite effective.

Like wise my .375H&H being my buff back up will be loaded with 350gr RNSN HD with SD of .356 @ 2275fps should be effective.

My buddy and his son have tuskless on the menu and are using .375 H&H 350gr NF FP solids, I don’t know the SD of this bullet but that’s a 270gr SP on the right for scale.

 

[matt85]

Bullet SD can be important... But it is just one aspect of a cartridge. Saying "SD is not important" would be the same as saying "velocity is not important".

People focus too much on individual specifications. You can compensate for low SD with bullet construction, velocity, or weight. Just like you can compensate for a low velocity with weight, SD, and bullet construction.

- My 8-bore has a very poor velocity, poor SD, and poor bullet construction. It makes up for this by leaning heavily into "weight" (1200gr bullets).
- I use a 300gr bullet in my 416, which has a poor SD. I compensate with velocity (2700fps) and bullet construction (solid copper).

Classic NE cartridges lean into SD to get the job done. SD can be extremely important!

 

[grand veneur]

Sectional density is nowadays only a theoretical guideline. The actual working of various bullets depends heavily on their design. Advanced designs of expanding bullets or solid copper bullets modified completely the original calculation model.

 

[BeeMaa]

Calling @michael458.

There are a number of factors that make a bullet penetrate, expand or blow up. And any of those can be the desired outcome. Sectional density is important, but I'd put it close to the bottom of the list. All of the factors above it will impact the sectional density to achieve the desired effect.

Material(s) used
Construction and heat treatments/process of bonding or forming
Bullet shape
Frontal area/tip shape
Length
Speed
Weight
Sectional density

This only really works when comparing similar bullets trying to achieve the same results. So take a 375H&H 270 grain TSX and compare it to a 300 grain TSX. Even then, it would depend on what I'm hunting , at what range and what outcome I'm looking for.

 

[MS 9x56]

It all boils down to a very simple choice. For dangerous game small diameter, lightweight bullets are bad. Large diameter, heavyweight bullets are good. Don’t make it so difficult.

 

[dogcat1]

I look at it but really don’t base a decision on it. I shoot mid range distances out to 500 yds but don’t hunt at that distance. It you are taking that long of a shot, get closer.

 

[coreydb]

I believe sectional density matters but is definitely not a main consideration for DG hunting. Correct me if I'm wrong folks, but this was initially for measuring lead bullets with brass sleeves. Bullets with high sectional density resist deflection and penetrate deep because they concentrate momentum into a smaller frontal area. Technological advancements in bullet design and composition created bullets that penetrate and resist deflection, but have a smaller sectional density.

 

[Wyatt Smith]

Op were you talking about solid bullets or expanding. It’s been proven that for solids it’s one of the least important factors for deep penetration, although some companies try to use it to cover up flaws in the more important like meplat size and nose profile.
For expanding bullets, especially lead core, it gives some idea about how much weight will be behind an expanded bullet. Once a bullet expands the SD has changed so having it higher to start with will help keep it high enough to penetrate. I will argue that it is still one of the least important factors behind bullet materials, jacket thickness, bonding, or monolithic.
In my opinion sectional density is only useful to compare bullets of different calibers to one another. As we all know a .308 200 grain bullet is heavier, and therefore has a higher SD, than a 150 grain bullet. But if one wanted to find a 338 bullet that would perform similarly to his 200 grain 30 caliber bullet the SD can be a useful tool to compare bullets of similar construction.

 

[AZDAVE]

For softs I still think the SD is important and give a rough idea of the penetration possibilities.

For solids with the CEB and Northfork style solids throw the SD out the window. as they penetrate so much better than the traditional round nose style solids. Just look at @michael458 in depth testing and make you own decision.