Sectional Density - Desert Dog

[deewayne2003]

I generally find this guy to be entertaining, and somewhat knowledgeable. I have found myself disagreeing with him on a handful of occasions, and this is certainly one of them. I am a believer in sectional density, but I guess he thinks it's bullshit. What do you think? Video below:

I think it’s important but not the end all be all of ballistics/ terminal performance like some people claim.

Example: The 350gr .423 Woodleigh Welcore has the SD of an ashtray.

On a 10 day hunt in Australia with a .404J I killed

5 water buffalo
2 Scrub bulls
2 feral horses
5 feral pigs

All clean kills and all performed flawlessly.

 

[CBeck]

it’s a great bullet if your doing longer range hunting but it does nothing inside of practical hunting distances. Better than older designs. I’ve shot literal thousands of rounds from 500-1700 yards and most people can’t consistently hit a pie plate ate 400 yards. so for most people I do not believe these bullets really matter but if you have the ability and like to hunt at longer ranges they are nice to have.

Most African hunting is done at practical distances, and extreme long-range performance isn’t necessary.

That said, I don’t really understand the criticism of bullets like the Terminal Ascent just because they were designed with high BC and extended-range capability in mind.

Most hunters want:

• The best scope (even if we rarely need more than 4–5x, many still run a 1.5–9x or similar — just in case)
• The most accurate rifle (less than a 1” group is trash)
• Consistent handloads or premium factory ammo

Why wouldn’t that same thinking apply to the bullet?

Terminal Ascent is essentially a modern version of the Trophy Bonded concept….. bonded construction, high weight retention, controlled expansion, and performance across a wide velocity range. It’s designed to work at any realistic hunting distance, not just long range.

If you’re never shooting past 200 yards, there’s still no downside to a bullet that flies more accurately, bucks wind better, and expands reliably across a broad range of impact speeds.

Better aerodynamics don’t make it a long-range-only bullet — they just make it a better bullet.

For what it’s worth, they shoot lights-out in my Hawkeye African in .280 AI, and performance on Southern whitetails at sub-100 yards has been excellent. Hard to argue with a premium bullet that works from near to far.

 

[Killingtime]

Most African hunting is done at practical distances, and extreme long-range performance isn’t necessary.

That said, I don’t really understand the criticism of bullets like the Terminal Ascent just because they were designed with high BC and extended-range capability in mind.

Most hunters want:

• The best scope (even if we rarely need more than 4–5x, many still run a 1.5–9x or similar — just in case)
• The most accurate rifle (less than a 1” group is trash)
• Consistent handloads or premium factory ammo

Why wouldn’t that same thinking apply to the bullet?

Terminal Ascent is essentially a modern version of the Trophy Bonded concept….. bonded construction, high weight retention, controlled expansion, and performance across a wide velocity range. It’s designed to work at any realistic hunting distance, not just long range.

If you’re never shooting past 200 yards, there’s still no downside to a bullet that flies more accurately, bucks wind better, and expands reliably across a broad range of impact speeds.

Better aerodynamics don’t make it a long-range-only bullet — they just make it a better bullet.

For what it’s worth, they shoot lights-out in my Hawkeye African in .280 AI, and performance on Southern whitetails at sub-100 yards has been excellent. Hard to argue with a premium bullet that works from near to far.



View attachment 747840

I like the TA and I load for it. It shoots and performs great for me.. some people I know have accuracy issues with it. The accubond is marketed as a modern version partition. People have claimed to have it fail in higher velocity cartridges at close ranges. I used to load it in a 257wby I now load ttsx, but like the 260ablr in my 375. Ultimate reloader built a 25creed and lowered velocity to just above claimed minimum of ttsx… it did not open up. Monos have a history of not opening up at extended shots when velocities drop to low. Not a issue for most practical hunting distances in Africa or anywhere.
My belief is all bullets work for what they are intended to do some better some worse. Like you said the TA is a great bullet and works in a whitetail at 100yards or 7-800 yards from your 280ai. But it is not necessarily any better at killing a hundred yard southern whitetail than any other bonded, mono or honestly cup&core bullet ( the only real downside for some is cost). I believe that distinction changes when we talk larger species like elk, moose, bear that’s where I believe it shines over other older bullets at all ranges. DG though which I think is what a lot of the SD conversation originated I’m not sure about.

Most of the High BC bullets are long for weight and caliber monos or thin jacketed long target bullets fine for deer not great at high speed on heavy animals.

I agree with you that the invention of some of these premium bullets that really are focused for hunting like the TA,Barnes LRX, hammer and ablr are better all around for close and far hunting for most species since the higher bc also translates to higher bullet weight and by extension high sectional density as well.

 

[CBeck]

My belief is all bullets work for what they are intended to do some better some worse. Like you said the TA is a great bullet and works in a whitetail at 100yards or 7-800 yards from your 280ai. But it is not necessarily any better at killing a hundred yard southern whitetail than any other bonded, mono or honestly cup&core bullet ( the only real downside for some is cost). I believe that distinction changes when we talk larger species like elk, moose, bear that’s where I believe it shines over other older bullets at all ranges.

That’s a fair point, and I agree with it completely.

For whitetails at typical distances, there’s no question that a lot of bullet designs will get the job done. I’m actually not one of the guys who thinks cup-and-core is obsolete — I still use and like traditional bullets like the Hornady InterLock and the Remington Core-Lokt. They’ve been killing deer cleanly for a long time.

In fact, I recently started a thread about the Hornady Big Game series and the decision to include the 270 InterLock. I was curious about the thinking behind keeping a traditional cup-and-core option in a lineup that also includes more premium designs.

That said, the general consensus here seems to be: why risk it? The bullet is the cheapest part of the hunt.

And I think that’s really the dividing line. For local whitetails, cup-and-core works just fine when used within its limits. But as the stakes go up — larger animals like elk, moose, or bear, tougher angles, higher impact velocities, or expensive hunts — that’s where premium bonded or monolithic bullets start to make more sense.

It’s not that traditional bullets don’t work — it’s just about margin for error when it matters most.

 

[Tradmark]

In the beginning of my time hunting i was shocked how much deeper barnes penetrated than much heavier cup and core bullets even when the barnes was much lower weight. The premium monolithic and bonded bullets really make smaller cartridges capable for game that they werent in years past. Some are just late to the party and its just not about 6.5’s on elk but more like allowing things like a 30.06 much much more effective on elk or brown bear or making the velocity cartridges like a 257w or a 300 weatherby live up to their potential

 

[PHOENIX PHIL]

I don't think SD is a B.S. number, but I do think the way it is applied can be incorrect. Section density IMO should only be applied when comparing bullet weights (and perhaps even caliber) of a specific design.

For example a 200gr .308 Nosler partition to a 180gr .308 partition. Or perhaps even a 7mm partition to a .308 partition. As has been noted, bullet construction and/or material(s) matter. If you use sectional density to compare bullets of two different designs and/or materials, you're now comparing apples to oranges. It just isn't useful and leads to erroneous comparisons.

I've never even heard of this Desert Dog guy before, but I believe his conclusions and what he's trying to argue are correct. That said, at the end of the video he states that some may find his presentation to be overly simplistic, count me in that group. Again I agree with his conclusion regarding SD, but his presentation is lacking in proving that.

 

[michael458]

SD does not seem to matter with mono bullets with the right bullet design. @michael458 did exhaustive tests on it.

I have covered this subject many many times, right here. I am going to attempt to be as brief as possible today, I have other projects, but this needs some light shed on it. I relented and watched this Desert Dog fellow, and he does have some good points, but the presentation is someone diluted and imprecise.

Old School Conventional thinking always brings up the importance of Sectional Density as a stand alone Factor. Its just easier to try and understand SD alone, than it is to figure out all the other factors that really are far more important.

There are many factors that supersedes and displaces Sectional Density to determine and define penetration.

Think about this. Here are a few examples of 400 gr .458 Caliber Bullets. All of them have a Sectional Density of .272. As long as they remain on the shelf, the SD will be the same forever. It is only when Terminal Penetration begins, that SD changes with some of these, in particular the expanding bullets and trauma inflicting bullets. Solid SD will remain the same, under most normal scenarios during terminal penetration. However, within the confines of "Solid Terminal Performance" there are 8 Known Factors of Solid Terminal Performance, leaving SD at #8, or the least important factor of the total.

Samples all with the same SD, All will penetrate to different depths of penetration because of other factors.

So ask yourself, "What does Sectional Density of Bullets sitting on the shelf tell you?"

Not much in my opinion, there are way too many other factors that come into play.

I break this discussion into two parts. Expanding and Trauma inflicting bullets and Solid Terminal Performance to show you the true values of SD and how other factors supersede SD in determining Terminal Penetration.

 

[uplander01]

I must be getting old, don’t like to shoot in Africa any further than 200 yards. Just bought and elegant 308 custom rifle, shoots 1/2” groups with 180gr Norma Alaska cup & core rn bullet hand loads going 2700 fps. I put a 1-4 s&b on it….call it a mini safari rifle. I’ll shoot this thing all year until it feels like an extension of my body, take it to Africa next year where nothing over 500-600 pounds is on the menu for me, and shoot stuff up like champion with this old school set up. To each his own, bow, rifle, handgun, spear, pick your method, archers have similar debates about broad heads, arrow weight, speed, draw weight. We have seemed to come full circle on bullets. Now you ca buy bullets that retain 95% of their weight no matter what, or you can buy bullets that are designed to basically explode into fragments. I think where the rubber meets the road with sd, momentum, weight, speed, is dangerous game hunting with solids, and ensuring you live through the process.

 

[michael458]

Expanding and Trauma Inflicting Bullets.

First, Sectional Density Changes dramatically with a Trauma Inflicting or Expanding Bullet, once it starts terminal penetration. Its beginning SD means nothing, because that changes the millisecond that Terminal Penetration Begins......... As the Bullet Expands in the case of a Premium, Swift A, Woodleigh, North Fork, TSX........ the Sectional Density # continues to get lower than what it began as.

On another thread here on AH somewhere, I dug out some of my older recovered bullets from buffalo and what have you. I measured the expansion of these bullets and the remaining weight to get the "Terminal Sectional Density". Some of these are old photos, and not as clear as I like, my apologies.

1. 500 Swift A Frame 458 Lott 2270 fps Buffalo weight 493 grs Expanded Diameter .824 inches
Terminal Sectional Density .104

2. 450 gr Swift A Frame 458 B&M Buffalo various, 3 recovered Bullets I believe just at or around 2200 fps Weight 444 gr diameter .785 average....... Terrible photo, sorry.
Terminal Sectional Density .103

3. 400 Swift A Frame 458 Winchester 2325 fps .800 expansion Diameter and retained weight of 385 grs...... Terminal Sectional Density .086

4. 500 Woodleigh Soft 2125 fps Buffalo retained weight 494 gr .902 expanded diameter...... Terminal Sectional Density .087

And now for some reason I cannot get this post to go to normal instead of BOLD. I am not trying to make a point with bold, it will not allow me to go back to normal size?????

Now, to show you just how different some expanding or trauma inflicting bullets are, and in particular with todays new Bullet Tech provided by CNC Machined Bullets. Here is the 420 Raptor by CEB, its mode of operation is vastly different than Conventional Expanding Bullets you see above, and will have a drastically different Sectional Density once Terminals begin. The Generation One Copper CNC and The Generation 2 Raptors have changed the world of Terminal Ballistics completely. The old rules no longer apply.

5. 420 CEB Raptor 458 B&M 2250 fps buffalo Retained weight 335 gr maximum terminal diameter (jagged points on front) .465 diameter
Terminal Sectional Density .221

Sitting on the SHELF, a 500 gr .458 caliber bullet has the SD of .341.

Sitting on the SHELF a 420 gr .458 caliber Bullet has the SD of .286

I don't believe "SHELF" SD means much.

Terminal SD of expanding/trauma inflicting bullets can show us the why, and the how. But about as far as it goes......... Pun Intended.......... Get It?

 

[michael458]

Solid Terminal Penetration and Performance


And here we are AGAIN;

There are 8 Absolute Known Factors for Solid Penetration and are as follows in Order of Importance.....

#1 Meplat Percentage of Caliber
Meplats that attain 65% Meplat of Caliber are terminally stable.... Above 70% Meplat bullets remain stable, however depth of penetration begins to decrease with every step up in meplat size. 70% Meplat or larger does increase trauma to, and destruction of tissue. 70% Meplats start to get difficult to feed, even in Winchester M70s...... From 65% Meplat to 68% Meplat is OPTIMUM for Stability, destruction of tissues, and feed and function in most quality rifles……….

Another consideration with Meplat Size, is actual Physical Size needs to be considered as well. From .458 caliber up, a 65% plus meplat of caliber will actually “Self Stabilize itself
during terminal penetration in aqueous medium/tissue up to on average 90% of the total penetration. This means a 65% meplat plus solid fired in a tight smoothbore, no rifling, no engraving on the bullet is stable during terminal penetration and requires nothing more. This is a result of actual physical size. A .458 caliber 65% meplat is .2977” across. We learned that in .416 caliber, 67% meplat with 400 gr bullets required at least a 1:12 twist rate to be 100% stable for the entire depth of penetration. Even though it has the required meplat size, it still relies on a faster twist rate to fully stabilize. A .416 caliber 67% meplat is .278”as compared to a .458 caliber 67% meplat at .307”. The larger physical size providing the additional stability without further aid.

#2 Nose Profile
There are many and varied Nose Profiles of solids on the market today, from the angled Nose Profiles of CEB and North Fork, to the straight nose profile of the older North Forks and GSC, the Barnes/Hornady Profiles (like a RN cut off at the top) to many more... Not all of these are created equal, and some are better performers than others. In recent tests in comparison between the old North Fork Profiles and the Newer North Fork Profiles I was getting 20% deeper penetration with the Newer North Forks than the older, with the same bullet, just difference in Nose Profile is all.... John at North Fork agrees, and in their work there they were getting more along the lines of 25% deeper penetration. One major thing that I noticed here, the stability at the end of penetration was 100% better. In most all tests here the last 2 inches of penetration of the old style North Forks would be unstable. Now this is and was of no consequence at the very end of penetration. The depth of penetration of these older nose profile bullets was always so deep that it had long accomplished its mission before loss of stability right at the very end. This new NOSE PROFILE of North Forks remains DEAD STRAIGHT to the very last of penetration, and always found NOSE FORWARD........

#3 Construction & Material
Construction of a solid is a major part of its ability to penetrate. To deny this is foolish to say the least. Some of our solids out there, lead core, are very very weak in construction and absolutely do not have the ability to bust through heavy bone and reach their intended targets. I have seen and have in hand failures of these bullets from the field..... A shame as well, as some of these bullets are promoted as Dangerous Game Solids, and some of them flatten out like pancakes when hitting heavy dense material. Some FMJ Have steel inserts, while this solves a problem in one area, it creates problems in other areas.... Brass is harder than Copper... No surprise there, but I have busted elephant heads with both copper and brass, and never had one distort, but, these solids were of a very STRONG NOSE PROFILE as well........ So you see, combinations of different factors work together to strengthen or weaken other factors..... A good strong Nose Profile, can overcome some material deficiencies and in the case of copper solids this is extremely important.



#4 Nose Projection
Nose Projection above the top bands was the last factor discovered. There may be more factors, but currently they remain undiscovered at this point in time.... We found that nose projection above the top of the bands of current CNC monolithic bullets is very important to depth of penetration. Some bullets designed to work through lever actin riflers require a SHORT NOSE PROJECTION in front of the bands so that they can be loaded deep enough to work through the actions of these guns... Nose Projection of these same bullets for bolt guns, single shots, and double rifles are longer, from .600 to .700 in front of the top band. The LONGER NOSE PROJECTION solids will penetrate on average 25% deeper than the shorter nose projection. Now, these bullets already have all the other required factors for stability, nose profile, construction and radius, so it is ONLY DEPTH Of penetration that is effected with properly designed bullets. The reason this occurs is “bubble drag”, the shorter nose projection means a longer base, the bubble created during terminal penetration in any aqueous medium/tissue collapses on the rear base of the bullet causing drag, and therefore less depth of penetration. The Longer Nose projection/shorter bullet base, the bubble is projected beyond the base of the bullet, therefore no drag is created, allowing for deeper penetration.


#5 Radius Edge of Meplat
We found that the radius edge of the meplat made a difference, small, but a difference none the less. A nicely radius edge penetrates about 5% deeper, and has more stability at the end than a sharp edged radius.... No more to go into here, thats it.......


All the Above Factors Deal with Bullet Design........

#6 Velocity
Velocity is a factor, but it also goes hand in hand with Nose Profile and Construction/Material. If we assume that the Meplat is optimum, the nose projection is optimum, and the bullet has a nice radius then velocity becomes a factor in combination with nose profile and construction/materials. Different Nose Profiles react differently with velocity. Some nose profiles at very low velocity cannot maintain stability, but this would be in the extreme, and other factors may come into play with some of this. In essence with some Nose Profiles, added velocity will equate to added depth of penetration, and of course trauma and destruction of tissue. Some nose profiles react better than others, but if properly designed, then all will get some gain from added velocity, UNTIL you reach the point that you get distortion of the meplat by TOO MUCH VELOCITY. Once you begin to distort that meplat, then all sorts of strange things begin to occur. One is depth of penetration will decrease, stability will decrease as well....... Normally you will only get this at extreme velocities at 2700-2800 fps or more, which in our big bore rifles is somewhat extreme.......... Lead core bullets will be effected in a serious manner at extreme velocities, followed by copper, and then brass........ Nose Profile and Construction & Material are very important for Factor #6.........



#7 Barrel Twist Rate
Barrel twist rate really only becomes a factor when Factor #1 is DEFICIENT....... If the meplat of caliber is undersized, less than 65%, then faster twist rates WILL INCREASE the depth of penetration by increasing the stability of terminal penetration. A 65% Meplat of Caliber can stabilize in slower twist rates of 1:18, or even slower...... I have seen 65% Meplat of Caliber stabilize with ZERO TWIST....... I have seen 50% Meplat of Caliber stability increase with faster twist rates, and have documentation to prove it, several times...... If you are using a properly designed Solid, then twist rate becomes less important, and more important if you are not using a proper designed solid. Fast Twist Rates can also increase stability of even RN Solids of decent design, hardly anything can increase stability of a more pointy RN FMJ.......


#8 Sectional Density
Sectional Density will ONLY BE A FACTOR with two bullets that are exactly the same in every other Factor or aspect. Factors #1 and #2 far outweigh Sectional Density in the terminal performance of Solids. We can take a properly designed 458 caliber 325 gr Solid and far out penetrate in depth and stability a poorly designed 550 gr 458 caliber bullet....... My son recently shot a medium sized elephant at 10 yards, perfectly executed side brain shot, with a 350 gr .474 caliber properly designed solid at 2200 fps. This bullet exited the head on the far side and still may be going for all I know. A 350 gr .474 caliber bullet has a sectional density of .223, and I personally would choose this little 350 gr bullet over the Woodleigh 500 gr RN FMJ at .4725 (ones I have here) any and every day for any mission............



These are undeniable facts, and can be proven over and over and over again in all test work, and these factors have been exercised in the field and have proven themselves in the field, many many times over...... These are the 8 Known Factors of Terminal Penetration of Solid Bullets.................

As you see Sectional Density is LAST.

Sectional Density of a 550 gr .458 caliber bullet is ..374

Sectional Density of a 325 gr .458 caliber bullet is .221

There are 7 other factors in Terminal Performance of Solids that supersede Sectional Density.

 

[uplander01]

Michael458, that's a volume of information right at your fingertips, if there was a mic-drop emoji, now is the time.

I agree, the science of ballistics is far more advanced and known than it once was.

 

[JG26Irish_2]

I'm waiting for Desert Dog to weigh in on this one..."somewhat knowledgeable," that's pretty rich. I can't think of any other YouTuber who has a broader AND deeper understanding of all things hunting, fishing, and guns who has more integrity in his videos than the Desert Dog. He and I have even disagreed on a non-related subject, but you have to respect his knowledge.

I have seen many of the DD's hunting video and I also agree that he is knowledgeable on hunting subjects. I know nothing of his technical ability or scientific background. The fact remains, that all other variables being equal, then Sectional Density (SD) is important because the bullet with the higher SD will carry its velocity longer and penetrate deeper for the SAME level of expansion. But.....

The variables are never all equal and even when you use two of the same design bullets, then the one with the higher SD will weigh more and will likely have a lower muzzle velocity then the lighter one with the lower SD. Obviously, velocity is another important variable for penetration. Then think of this, penetration is only important until the bullet penetrates all the way thru the animal. After that, it no longer matters. I think the best way to look at it is that SD is only one of the important variables when choosing a hunting bullet and as long as you choose a good bullet and place it well, then you will be a successful hunter. I too, like heavy for caliber in most of my big game bullets. 180g for a 308 has given me one shot kills, every time. Not most of the time. Every time. I like bonded bullets but also use Barnes monos a lot and both work very well. Yes, for the same bullet weight, the mono will penetrate more. Why? First it tends to expand less in total to about 2x diameter but also because it will have a higher SD than the same weight lead core bullet. Snap.

This enables a hunter to go one weight class lighter with a mono and still get the same or similar penetration. That is usually good. But, there are other issues with the monos. Example: If you drive them too fast or shoot an animal up close with them at magnum velocities, they sometimes shed all or some of there petals and that can be a problem. Another issue with monos it that if you shoot them into animals at too slow a velocity, they will fail to expand and that can lead to a slower kill. It will kill if you placed it well but you may be in for a tracking job. I like to limit my effective range to the distance where the impact velocity drops to 2000fps. This is very important with monos but is important with any expanding bullet. You just have more room for error with the lead core type.

In summary - SD matters. It is just not the only factor in a very complex equation. My advice is to choose a quality bullet, such as bonded core, monolithic, partition, etc, choose an accurate load, choose slightly heavy for caliber and limit impact velocity to 2000fps minimum. And also limit your effective range to groups that are half the size of the kill zone for your chosen quarry. Do that because, in the hunting fields, too many things combine to affect your hunting accuracy. Memorize your ballistic chart so you can place that bullet well every time and you will be successful.

Last word is that myself, my son and two other hunters just got back from a Texas Nilgai hunt. Nilgai are famous for being tough as nails. Three of us killed Nilgai that dropped in their tracks. DRT. All three of us used 338wm rifles. Two of those used 225g Barnes TTSX and one used Nosler 225g AccuBond. The fourth hunter used Barnes TTSX 200g in a 300wm rifle. His Nilgai ran about 150y and had to be finished. To be clear, the other Nilgai each got a finishing shot but they never regained their feet after the first impact. All four of us bagged our prey and were successful, not due to our bullet's SD or even its construction. We all hit the kill zone with a bullet that was big enough and fast enough to penetrate to the vitals and do its job. The rest was details.

 

[Wyatt Smith]

One thing about sectional density is that it changes after expansion. Really the only thing it tell us for certain is how heavy the bullet is per caliber.

 

[Killingtime]

Solid Terminal Penetration and Performance


And here we are AGAIN;

There are 8 Absolute Known Factors for Solid Penetration and are as follows in Order of Importance.....

#1 Meplat Percentage of Caliber
Meplats that attain 65% Meplat of Caliber are terminally stable.... Above 70% Meplat bullets remain stable, however depth of penetration begins to decrease with every step up in meplat size. 70% Meplat or larger does increase trauma to, and destruction of tissue. 70% Meplats start to get difficult to feed, even in Winchester M70s...... From 65% Meplat to 68% Meplat is OPTIMUM for Stability, destruction of tissues, and feed and function in most quality rifles……….

Another consideration with Meplat Size, is actual Physical Size needs to be considered as well. From .458 caliber up, a 65% plus meplat of caliber will actually “Self Stabilize itself
during terminal penetration in aqueous medium/tissue up to on average 90% of the total penetration. This means a 65% meplat plus solid fired in a tight smoothbore, no rifling, no engraving on the bullet is stable during terminal penetration and requires nothing more. This is a result of actual physical size. A .458 caliber 65% meplat is .2977” across. We learned that in .416 caliber, 67% meplat with 400 gr bullets required at least a 1:12 twist rate to be 100% stable for the entire depth of penetration. Even though it has the required meplat size, it still relies on a faster twist rate to fully stabilize. A .416 caliber 67% meplat is .278”as compared to a .458 caliber 67% meplat at .307”. The larger physical size providing the additional stability without further aid.

#2 Nose Profile
There are many and varied Nose Profiles of solids on the market today, from the angled Nose Profiles of CEB and North Fork, to the straight nose profile of the older North Forks and GSC, the Barnes/Hornady Profiles (like a RN cut off at the top) to many more... Not all of these are created equal, and some are better performers than others. In recent tests in comparison between the old North Fork Profiles and the Newer North Fork Profiles I was getting 20% deeper penetration with the Newer North Forks than the older, with the same bullet, just difference in Nose Profile is all.... John at North Fork agrees, and in their work there they were getting more along the lines of 25% deeper penetration. One major thing that I noticed here, the stability at the end of penetration was 100% better. In most all tests here the last 2 inches of penetration of the old style North Forks would be unstable. Now this is and was of no consequence at the very end of penetration. The depth of penetration of these older nose profile bullets was always so deep that it had long accomplished its mission before loss of stability right at the very end. This new NOSE PROFILE of North Forks remains DEAD STRAIGHT to the very last of penetration, and always found NOSE FORWARD........

#3 Construction & Material
Construction of a solid is a major part of its ability to penetrate. To deny this is foolish to say the least. Some of our solids out there, lead core, are very very weak in construction and absolutely do not have the ability to bust through heavy bone and reach their intended targets. I have seen and have in hand failures of these bullets from the field..... A shame as well, as some of these bullets are promoted as Dangerous Game Solids, and some of them flatten out like pancakes when hitting heavy dense material. Some FMJ Have steel inserts, while this solves a problem in one area, it creates problems in other areas.... Brass is harder than Copper... No surprise there, but I have busted elephant heads with both copper and brass, and never had one distort, but, these solids were of a very STRONG NOSE PROFILE as well........ So you see, combinations of different factors work together to strengthen or weaken other factors..... A good strong Nose Profile, can overcome some material deficiencies and in the case of copper solids this is extremely important.



#4 Nose Projection
Nose Projection above the top bands was the last factor discovered. There may be more factors, but currently they remain undiscovered at this point in time.... We found that nose projection above the top of the bands of current CNC monolithic bullets is very important to depth of penetration. Some bullets designed to work through lever actin riflers require a SHORT NOSE PROJECTION in front of the bands so that they can be loaded deep enough to work through the actions of these guns... Nose Projection of these same bullets for bolt guns, single shots, and double rifles are longer, from .600 to .700 in front of the top band. The LONGER NOSE PROJECTION solids will penetrate on average 25% deeper than the shorter nose projection. Now, these bullets already have all the other required factors for stability, nose profile, construction and radius, so it is ONLY DEPTH Of penetration that is effected with properly designed bullets. The reason this occurs is “bubble drag”, the shorter nose projection means a longer base, the bubble created during terminal penetration in any aqueous medium/tissue collapses on the rear base of the bullet causing drag, and therefore less depth of penetration. The Longer Nose projection/shorter bullet base, the bubble is projected beyond the base of the bullet, therefore no drag is created, allowing for deeper penetration.


#5 Radius Edge of Meplat
We found that the radius edge of the meplat made a difference, small, but a difference none the less. A nicely radius edge penetrates about 5% deeper, and has more stability at the end than a sharp edged radius.... No more to go into here, thats it.......


All the Above Factors Deal with Bullet Design........

#6 Velocity
Velocity is a factor, but it also goes hand in hand with Nose Profile and Construction/Material. If we assume that the Meplat is optimum, the nose projection is optimum, and the bullet has a nice radius then velocity becomes a factor in combination with nose profile and construction/materials. Different Nose Profiles react differently with velocity. Some nose profiles at very low velocity cannot maintain stability, but this would be in the extreme, and other factors may come into play with some of this. In essence with some Nose Profiles, added velocity will equate to added depth of penetration, and of course trauma and destruction of tissue. Some nose profiles react better than others, but if properly designed, then all will get some gain from added velocity, UNTIL you reach the point that you get distortion of the meplat by TOO MUCH VELOCITY. Once you begin to distort that meplat, then all sorts of strange things begin to occur. One is depth of penetration will decrease, stability will decrease as well....... Normally you will only get this at extreme velocities at 2700-2800 fps or more, which in our big bore rifles is somewhat extreme.......... Lead core bullets will be effected in a serious manner at extreme velocities, followed by copper, and then brass........ Nose Profile and Construction & Material are very important for Factor #6.........



#7 Barrel Twist Rate
Barrel twist rate really only becomes a factor when Factor #1 is DEFICIENT....... If the meplat of caliber is undersized, less than 65%, then faster twist rates WILL INCREASE the depth of penetration by increasing the stability of terminal penetration. A 65% Meplat of Caliber can stabilize in slower twist rates of 1:18, or even slower...... I have seen 65% Meplat of Caliber stabilize with ZERO TWIST....... I have seen 50% Meplat of Caliber stability increase with faster twist rates, and have documentation to prove it, several times...... If you are using a properly designed Solid, then twist rate becomes less important, and more important if you are not using a proper designed solid. Fast Twist Rates can also increase stability of even RN Solids of decent design, hardly anything can increase stability of a more pointy RN FMJ.......


#8 Sectional Density
Sectional Density will ONLY BE A FACTOR with two bullets that are exactly the same in every other Factor or aspect. Factors #1 and #2 far outweigh Sectional Density in the terminal performance of Solids. We can take a properly designed 458 caliber 325 gr Solid and far out penetrate in depth and stability a poorly designed 550 gr 458 caliber bullet....... My son recently shot a medium sized elephant at 10 yards, perfectly executed side brain shot, with a 350 gr .474 caliber properly designed solid at 2200 fps. This bullet exited the head on the far side and still may be going for all I know. A 350 gr .474 caliber bullet has a sectional density of .223, and I personally would choose this little 350 gr bullet over the Woodleigh 500 gr RN FMJ at .4725 (ones I have here) any and every day for any mission............



These are undeniable facts, and can be proven over and over and over again in all test work, and these factors have been exercised in the field and have proven themselves in the field, many many times over...... These are the 8 Known Factors of Terminal Penetration of Solid Bullets.................

As you see Sectional Density is LAST.

View attachment 748092View attachment 748093View attachment 748094

Sectional Density of a 550 gr .458 caliber bullet is ..374

Sectional Density of a 325 gr .458 caliber bullet is .221

There are 7 other factors in Terminal Performance of Solids that supersede Sectional Density.

First off sir thank you for the in-depth information this is amazingly detailed. Second off that 325gr penetration is insane!!

 

[michael458]

Well this is odd............ I noticed the order of some of my photos, are out of place now? My first post this morning, the "In General" conversation, showed "Shelf Bullets" in the beginning, and later the fired and tested bullets. Now the Shelf bullets are on the bottom, the fired on top?

Then, on the Solid post, the Test 325 CEBs are on the bottom, and the one recovered from elephant on the top, in my original post, it was reverse that............ ??

Then I noticed our "Friendly Moderator" had visited each post? Did our Friendly Moderator rearrange the order of my photos? And Why? Or, just a system glitch of some sort? I had those in order to make a point.................

Odd................

 

[DaddyFlip]

All three of us used 338wm rifles. Two of those used 225g Barnes TTSX and one used Nosler 225g AccuBond. The fourth hunter used Barnes TTSX 200g in a 300wm rifle. His Nilgai ran about 150y and had to be finished. To be clear, the other Nilgai each got a finishing shot but they never regained their feet after the first impact. All four of us bagged our prey and were successful, not due to our bullet's SD or even its construction. We all hit the kill zone with a bullet that was big enough and fast enough to penetrate to the vitals and do its job. The rest was details.

Curious for clarity... does Barnes make a .308 TTSX in 200gr? It's not in their catalog. Maybe it was the LRX, which looks like a TTSX but with slightly different construction (?). I would guess an LRX and a TTSX are close in construction, but if the LRX marketing materials are to be trusted, it should "blow up" more readily than a TSX or TTSX. Not my point; my point was to say that the 200gr 300WM projectile had a higher SD than any of the 225g 338WM projectiles and they were probably traveling about the same speed +/- 100fps. And yet, who would argue that the 338WM is the more powerful option?

 

[DaddyFlip]

Here's why static SD doesn't matter. I'll point out an extreme example then folks can make up their own mind about the rest. A 100gr 243 bullet has the same sectional density as a 300gr 416 bullet. I used Hornady's bullet list to make the chart and added weight labels for some of the calibers. It's easy to see that SD increases as bullet diameter decreases at the same weight. It's less easy to understand the relevance of SD when looking at the same SD across calibers as weight increases. Enjoy!

 

[Cheesehead]

SD is just a mathematical expression of the relationship between bullet weight and diameter, nothing more, nothing less. I don't think it has much utility as a standalone value, but it is still useful for comparing similar projectiles. For example, in @michael458 's post discussing the .458 projectiles above, the 450 gr Swift A-frames out-penetrated the 400 gr A-frames. And I remember in previous post discussing the CEB solids, the 450gr solids out penetrated the 325 gr solids shown in this thread.

 

[DaddyFlip]

SD is just a mathematical expression of the relationship between bullet weight and diameter, nothing more, nothing less. I don't think it has much utility as a standalone value, but it is still useful for comparing similar projectiles. For example, in @michael458 's post discussing the .458 projectiles above, the 450 gr Swift A-frames out-penetrated the 400 gr A-frames. And I remember in previous post discussing the CEB solids, the 450gr solids out penetrated the 325 gr solids shown in this thread.

I agree, and you don't need the SD number to tell you that the heavier projectile is going to penetrate more/better than the lighter projectile in the same caliber.

 

[Miletic]

If, for example, we take the same expansive bullets sent at different speeds into the body of a wild animal, the one that was sent at a lower speed will go deeper. Of course, there is a limit to this. A higher speed spreads the projectile more, and if it is not monolithic or bonded, it takes more mass from it. We all know that a firm and hard grain will penetrate deeper. But when it comes to soft point and plastic nose projectiles speed is very important. I did some research several times and tested different projectiles at different velocities. SD participates in the construction of the projectile and thus has to do with penetrat