Does anyone have an idea of the minimum sectional density of a bullet suitable for game?

For example, if I want to hunt deer, what is a good number? Black Bear? Moose?

It would seem to me that some knowledgable fellow would have posted numbers of this nature somewhere.

Thanks,

RobertD

Sectional density means little without knowing the bullet construction.A barnes x or failsafe can have a much lower sectional density and still perform better on game than most conventional bullets with much higher sectional densities.Having a partition or bonded core also makes a big difference.

Yes, this is correct. Once a bullet starts to expand, the sectional density really drops.

I was speaking in the general sense. I thought there might be a list of min sectional densities for various game somewhere.

RobertD

I'm sure that someone, somewhere has come up withthese charts and numbers, but like Stubblejumper says, bulet construction is more important...

What cartridge are you using?

If for instance, you had a 30-06, and where hunting moose, I'd suggest a 180gr or heavier bullet if it was 'conventional.'

I'd suggest a 168gr X bullet or 165gr Failsafe if that floated your boat

There is WAy too many variables out there these days

As noted before, bullet construction has alot to do with penetration etc...but as a general rule, for deer, bullets with SD's of .225-.266 are good, and for larger game, bullets with SD's of .271-.313 are great.

But a 140 gr. Barnes X is a better elk bullet than a 162 gr. A-Max (i won't mention MatchKings )

If you are using "like" lead filled bullets then SD may mean something. If you are using solid copper bullets, it doesn't mean anything at all. Its just a number then.

What cartridge are you using?

Don

Hey RobertD, Quite a few years ago as a Deer was being cleaned, a very young guy spotted his spent bullet next to the hide and retrieved it. As I continued cleaning the Deer he washed off the bullet and studied it closely.

All of a sudden he looks over at us and says, "I know why it didn't Exit! The Sectional Density is almost nothing."

Everyone smiled and I went on about the task at hand. But, the boy had a very interesting point. As we discussed it after dark with a touch of Liquid Corn to enhance the thought process, the more valid his point became.

Ballistic Coefficient gets the bullet to the Point-of-Impact with a certain amount of retained Energy and along a specific flight path. Once the bullet reaches the Game, the retained Sectional Density coupled with the Impact Velocity is what "typically" drives the Bullet in:
1. A narrow channel(FMJ, Solids)
2. Widens a bit and Exits(FailSafe, BarnesX, Partition, etc.)
3. Widens more and Exits(180gr Hornady, Hot-Cor, CoreLokt, etc, in a 30-06 at 100yds, etc.)
4. Widens farther and stays inside(150gr Boat Tail in a 300WinMag at 100yds, etc.)
5. Explodes like a grenade(fragile Varmint bullets at high Impact)

And of course, there are exceptions to those situations. But it is very interesting to take a bullet design and think about what it "typically" does after Impact by recalculating the S.D. and compare it to what it originally was.

As for a properly designed Solid, no change in the S.D. should occur. And at the other extreme, a 35gr Plastic Tip Varmit bullet sent from a 22-250 and Impacting at 100yds is where the S.D. will reach 0.000 due to total destruction.

So, I guess I disagree with those that believe S.D. is no longer of any value. No doubt the Design Envelope of Bullets has changed since we only had Cup Bullets, but the reason we get such d-e-e-p(FailSafe, BarnesX, Solid, Partition, etc.) penetration is still due to a higher retained S.D. coupled with a decent Velocity once Impact has occurred.

The young fellow was right!

[ 11-16-2003, 15:48: Message edited by: Hot Core ]

Bullet shape not sectional density determines ballistic co-efficient.A lighter spitzer boatail will have a much higher ballistic co-efficient than a heavier flat based round nose.

To help everyone out, here are the formulas:

Sectional Density(SD) equals the Weight(W) of the bullet in grains divided by 7000(grains in a pound) times the bullet Diameter(D) in inches squared.

SD=W/(7000xDsq.)

A 165gr 0.308" Speer Boat Tail:

165 / (7000 x 0.308 x 0.308) = 0.248 S.D.

...

Ballistic Coefficient(BC) equals the Sectional Density(SD) divided by the coefficient of Form(I).

BC=SD/I

Same bullet

0.248/0.459 = 0.540 B.C.

...

Both Formulas are from P.O. Ackley's, "Handbook for Shooters & Reloaders" along with the Form Factors.

I think what the poster was refering to was a chart or reference by Rick Jamison??? Was an article or rough guestimates for SD numbers for various sized critters. If that's correct, sorry I can't help. Have stacks and stacks of old mags, but too hard to find.

I just read an article on this, I believe in Rifle Shooter? Anyway, it was suggested that you have .210 for deer size, .260 for elk size, and .300 for larger game.

Bob257

Bob257 has the answers to the question. Thanks to all who posted, as the replies were most interesting.

The folks who commented that bullet design outweighs SD is correct, although for a given bullet design, a higher SD will penetrate farther.

The reason the question came up in my mind is that it doesn't take much to penetrate all the way through a deer or an antelope, so why pick a heavy for caliber bullet if you already picked a good quality bullet design? Pick a good construction and go with an SD with some extra margin.

On the other hand, it does take a bit to penetrate an elk or a moose, so the min SD for that would logically be higher.

Finn Aagard did an article some time back on the magnitude of the SD after the bullet expanded. He found that sometimes, smaller calibers out penetrated larger calibers even though the smaller bullet had expanded to a larger diameter than the larger caliber bullet. If I remember correctly, he compared a 250g from a 35 Whelen to a 270g from a 375 H&H and the Whelen penetrated farther and open up more than the bullet from the H&H. When he calculated the SD, the Whelen had a higher number even with the increased expansion.

If I can find the article, I will post it.

Thanks, RobertD

Robert,

"The folks who commented that bullet design outweighs SD is correct, although for a given bullet design, a higher SD will penetrate farther."

Correct with same material bullets.

Our tests have shown when comparing a solid copper bullet against the lead filled bullet the solid copper bullet penetrates much better. Copper is simply tougher/stronger then a lead filled bullet. The lead filled bullet mushrooms to a larger degree and that larger frontal diameter slows penetration. The SD for a solid copper bullet means less then that of a lead filled bullet when it comes to penetration. The geometric shape plays a large role in penetration when using a solid copper bullet.

Don

I think this article by Chuck Hawks is what you are looking for ...
can�t remember the exact site where it was ...

The Sectional Density of Rifle Bullets

By Chuck Hawks

Sectional density (SD) is the numerical result of a calculation that compares a bullet's weight to its diameter. To calculate a bullet's sectional density divide the bullet's weight (in pounds) by its diameter (in inches), squared. The higher the SD number the better the SD, and the heavier a bullet is in proportion to its diameter.

SD is important because it has a significant effect on penetration. Other things being equal (like impact velocity, bullet design and material, etc.) the higher the SD number, the better the bullet's penetration. In other words, a skinny bullet of a given weight tends to penetrate better than a fat bullet of the same weight, because it concentrates the same force on a smaller area of the target. For example, if other factors are equal, a 150 grain .270 bullet will penetrate better than a 150 grain .35 caliber bullet.

Penetration is important because the bullet must get well inside an animal to disrupt the functioning of its vital organs. A bullet that fails to penetrate the fur, skin, muscle, and bone necessary to reach the vital organs is very unlikely to bring an animal down.

SD stays the same for all bullets of the same weight in the same caliber--shape does not affect SD. This information is important to remember when comparing rifle bullets.

--------------------------------------------------------------------------------

Here are some typical hunting bullets and their sectional densities, which are recognized as effective for medium size big game animals:

.243" (6mm) 90 grain, SD .218
.243" (6mm) 100 grain, SD .242
.257" (.25) 100 grain, SD .216
.257" (.25) 115 grain, SD .249
.264" (6.5mm) 120 grain, SD .247
.277" (.270) 130 grain, SD .242
.284" (7mm) 140 grain, SD .248
.308" (.30) 150 grain, SD .226
.308" (.30) 165 grain, SD .248
.321" (8mm) 170 grain, SD .236
.338" (.338) 200 grain, SD .250
.358" (.35) 200 grain, SD .223

As you can see, all of the above have a sectional density over .215, and the average is about .237. That is the kind of SD you should look for in a bullet for medium game.

--------------------------------------------------------------------------------

For large game bullets with higher sectional density should be chosen. Good examples of such bullets would be:

.264" (6.5mm) 140 grain, SD .287
.277" (.270) 150 grain, SD .279
.284" (7mm) 160 grain, SD .283
.308" (.30) 180 grain, SD .271
.321" (8mm) 200 grain, SD .274
.338" (.338) 225 grain, SD .281
.358" (.35) 250 grain, SD .279
.375" (.375) 270 grain, SD .274
.458" (.45) 400 grain, SD .272

All of the bullets immediately above have a sectional density over .270. The average SD of these bullets is about .279. Bullets of this sectional density, if well constructed, have proven able to penetrate deep into big game animals.

--------------------------------------------------------------------------------

I did a quick survey of the hunting bullets with SD's over .300 available in common factory loads and to the reloader in the various rifle calibers. These are the top calibers and bullet weights for maximum penetration:

.264" (6.5mm) 160 grain, SD .328
.284" (7mm) 175 grain, SD .310
.308" (.30) 200 grain, SD .301
.308" (.30) 220 grain, SD .331
.321" (8mm) 220 grain, SD .301
.338" (.338) 250 grain, SD .313
.375" (.375) 300 grain, SD .305
.416" (.416) 400 grain, SD .330
.458" (.45) 500 grain, SD .341

Most people will not be surprised to find the heavy .338, .375, .416, and .458 bullets on the above list. But many may be surprised to find that the heavy weight bullets for the common 6.5mm, 7mm and .30 calibers are right in there with the best medium bore and elephant gun bullets. Which may help explain why these small bore calibers are so versatile.

END OF ARTICLE

Afrikaander
A very good input indeed!!

I guess I will take the liberty to quote you on some of this in an article.

"For example, if other factors are equal, a 150 grain .270 bullet will penetrate better than a 150 grain .35 caliber bullet."

The shape of the bullet plays a role in the example listed above. The smaller diameter allows for better penetration - all else being the same.

"SD stays the same for all bullets of the same weight in the same caliber--shape does not affect SD. This information is important to remember when comparing rifle bullets."

Correct, shape does not affect SD but shape does affect penetration as does material. Therefor it is important to take into consideration the shape and construction of the bullet - solid copper versus a lead filled bullet, as one example.

Because copper is stronger/tougher then a lead filled bullet it will penetrate better, all else being equal. Therefor when dealing with a solid copper bullet the SD doesn't have as much influence on penetration as compared to a like lead filled bullet. The bullet shape and construction play a huge role in penetration - made from solid copper.

Don

The enemy of these long bullets is tumbling and bending which can seriously effect both penetration and bullet path. Twist must be more than just enough if tumbling in game is to be avoided. Bending is a more serious problem and was what (I'm told) made Bell move from 6.5x54 160gr to 7x47 175gr

Just a couple of opinions....In the cases of deer and antelope, none of this much matters if shot placement is good. These animals are killed rather easily regardless of bullet construction. There are hundreds of examples of hunters on this board alone that will argue the virtues of everything from 223 to 500 nitro and everything between for deer.

The case for bullet composition is also interesting. The copper bullets are, most certainly built from different materials, but I don't think that is the main reason for their penetration results. Traditional lead core bullets are designed to expand to a much deeper level within the bullet, which disrupts penetration while the coppers are designed to expand a little (very little), probably shed their petals, and essentially become a solid or FMJ bullet. This "construction", or lack of it, is what causes the penetration, not the composition. If coppers were made to expand to the same point within the bullet (2/3 the bullet length)as the lead cores are, then I think we would see similar penetration from both types. At that point, I don't know if the coppers would hold up under pressure or velocity without flying apart because it is very hard to change the cohesive properties of solid copper like it is for a lead alloy. Basically, would a .264 copper bullet hold up at 3000 fps with a hole 2/3 the way down it and still have a hole big enough to allow expansion, or would it immediately begin to come apart?

Please don't think I am putting down the coppers. I am not. They are great for what they are designed to do which is expand minimally shed petals and penetrate through an animal. They are definately for the complete penetration crowd, of which I am one.

As to sectional density, it is specifically why I like my 6.5s so much. Check any of the charts above and see which bullets have the high densities at the lowest weights. For me this is as much a lowering or recoil, or increase in velocity because of the lower recoil as much as anything. I will admit that it is not much as far as recoil goes in similar weights, but I would rather shoot a 120 6.5 bullet at 3500 fps than a 200 grain 338 st the same velocity and sectional density. I don't know if that made sense...oh well.

Larrys,

You bring up some very good points.

Not to speak for any other solid copper bullet manufacturer but Groove Bullets. We manufacture various "types" of bullets for various purposes, as most manufacturers do.

With regard to the front of the bullet coming apart (loosing it petals) and the back of the bullet not expanding much, allowing additional penetration, that is one "type" of bullet that we manufacture. Our designation for that type of bullet is EXP (expanding). Our EXP type is designed to shred its petals inside the animal, causing internal trauma, then the back of the bullet drives on through to provide a bleeder hole. The back of the bullet doesn't expand much and therefor provides for additional penetration over a bullet that does expand a lot. The lessor frontal area allows the bullet to drive forward with decreased meat damage.

We also manufacture a S-EXP (semi-expanding) type that has a shallower hollow point and is made for applications where increased penetration is wanted. The N-EXP (non-expanding) type is made for high penetration and doesn't have a hollow point at all.

With regards to the bullets tumbling, our testing hasn't shown that to be the case, using Groove Bullets. I can't speak for other bullets.

There are many different types and materials of bullets for varying situations. Using the "proper" bullet for the job at hand should net very good results.

The material/composition and type of bullet will provide more or less penetration.

Don

In my opinion with convetional Lead core bullets, I like to see "minimum" SD of .226 for deer size game (in centerfire rifle calibers, a little lower for revolvers). For Big game like moose,Elk, I like to see a minimum SD around .266

Now when you start talking about copper bullets like Groove, and Barnes, That is a whole new ball club and SD is really an obsolete measure.

SD is also the primary determinant of the number of diameters a given bullet is capable of expanding to. A high SD bullets simply has more material to use in forming a large mushroom than low SD bullets. In this manner a 300 gr 338 can leave the same wound channel as a 300 gr 375 bullet.

Woodleigh bullets BC and SD for all calibers. Look at the SD of the .33 bullets; this will give you an idea of why .338's are so popular with big game hunters in Alaska:

http://www.woodleighbullets.com.au/Bullets.html

According to the SD formulas here, a 220 grain 35 cal bullet with an SD of 245 isnt enough for Elk, its a deer bullet. Same with a .375 235 grain, sd 239. A 300 grain 44cal bullet and a 350 grain .458. Sorry but I aint buyin it.. Id use any one of those on Elk in a heartbeat and they would work as well as anything.

I wonder what the SD of a .50 caliber round ball is.. If we looked it up Ill bet it wouldnt qualify for anything more than a jack rabbit.