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Thread: Speed vs. Sectional Density

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    Member Bighorse's Avatar
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    Default Speed vs. Sectional Density

    I'm the new owner of a 416 Ruger. As such I've been thinking of Why? a bit more lately. Just recently my wife killed a brown bear at 20 yrds with a 25-06 shooting 120g nosler partitions. Two shots, first was high shoulder with bone inmpact, complete pass, second heart, pass. So what I've observed is at close range it seems to me that a properly constructed bullet beeing propelled at speed with sufficient rotation imparts alot of energy very quickly into game. Not the same kind of energy transfer for frangible bullets just to clarify that bullet choice is important in this discussion. Would the 416 kill better, I can't imagine.

    So now that I've got this big bore. I'm considering what kind of energy trasnfer I'm looking at. The term sectional density seems to come up often. What does that mean? Will I get more penetration over a broader range? Will I have a higher energy transfer?

    I also want to load it up with 300g bullets, the lightest I can find and optimize this caliber for long range alpine pursuits. Has anyone loaded it with 300g Nosler Partitions and worked up balistics here?

    Thanks

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    Bighorse,

    Congrats on the new rifle! I've been interested in the 416 Ruger, so I'll be following your thread to read what folks have to say about it. I went to MidwayUSA site and they offered only the Barnes bullet in the 300 grain offering. I wanted to find the ballistic coefficient to plug it into the Berger Ballistics Program to see what the calculated bullet drop and the calculated energy levels are at a given range. I'm sure that any ballistics program has limitations when judged against it's real-world applications, but the computer programs can give you a place to start....so I'll include the link below.

    As for max distance (and I know there will be other forum members with differing opinions)... I called Barnes and Swift and asked what the impact velocity needed to be and, if I recall correctly, it was just under or at the 1800 FPS point at animal impact.

    http://www.bergerbullets.com/Ballist...ram/index.html

    Not sure I offered anything that can help you but I hope I did. Take care!

    MyTime

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    Member hodgeman's Avatar
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    Sectional Density is calculated with the following formula-- SD= (mass)/ (area).

    In bullets the bore is a fixed size so all bullets of the same caliber have the same cross sectional area, the only variable is mass. On bullets of similar construction a heavier bullet is a longer bullet.

    With a uniform amount of force, a long skinny projectile will penetrate a medium better than a bigger diameter but shorter one. Ie. a long, heavy for caliber rifle bullet will outpenetrate a musket ball or pistol bullet given equal weight and velocity.

    The SD number published is useful for comparing bullet profiles of varying calibers. As rule of thumb- a bullet of high sectional density with outpenetrate one of low sectional density.

    The really successful cartridges of years gone by all featured long, heavy bullets nearly across the board despite some pretty meager velocity numbers...that should tell you something.

    I don't get wrapped around the axle about energy numbers....you can get some impressive numbers with light bullets at high velocity but the low sectional density will limit penetration if bullet construction doesn't limit it even more.

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    Supporting Member Amigo Will's Avatar
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    I have found that fast and small leave little holes through bone where big slow bust the bone and make little bullets out of the splinters. At 20 yards I believe the bones would be much more damaged from the big/slow makeing a charge harder
    Now left only to be a turd in the forrest and the circle will be complete.Use me as I have used you

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    are you confusing "ballistic coefficient" with "sectional density" ? in mentioning "alpine" hunts I began to wonder as I am sure some would use the .416 for long shots but I would bet more would opt for a smaller caliber and maybe use a heavy for caliber weight bullet - I would expect that the "computer" calculations for a long range shot with a .416 / 300 projectile will be unimpressive by ordinary standards, and I am not saying it should not or cannot be done ... I, personally, would not have intentionally used a 25.06 on a brownie ! (JMO) but I'm glad it turned out "OK"

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    Well it's the third bruin to fall to the 25-06. Two Brownies and an Black bear all respectible boars. No giants but big bears.

    I'm not confusing the two terms. It's just when you start talking about big bores when doing my research sectional density brought up much more than when talking smaller calibers. Then you talk speed and balistic coefficient more.

    How far than would that 300 barnes travel before it dropped to that 1800 fps if it leaves the barrel at 2500fps? That would essentially dictate range. Is the Balistic coefficient better for the Nosler Partition or the Barnes X in the 300g .416 bullet? It's hard to find good BC 300g bullets for this gun.

    I wouldn't be shooting out past 300 yrds with this iron. It's beyond my skill. I bought this iron as a bear defence weapon for the river valleys until I hit the alpine. So with QD rings and iron sights I will pack 400g thumpers for the valley and want to work up 300g midrange rounds for alpine shots.

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    At one time, sectional density was useful as a predictor of penetration. All bullets were made of a lead core with copper/gilding metal/mild steel jackets and s.d. numbers were helpful in comparing various calibers with one another when selecting or designing new bullets. If you are using cup and core bullets these numbers are still helpful, but with the changes to bullets in the past 25 years or so this is a less helpful predictor IME. That is to say that a monolithic expanding bullet (i.e. Barnes X, TSX or the like) behaves very differently than a bonded lead core bullet or a plain cup & core bullet all of similar weight and caliber. Composition and construction can overcome or devalue any s.d number that a particular bullet may have. For example every 150 grain .308 caliber bullet has a sectional density of .226 whether it is a NBT, NPT, Speer RN or TSX. Fired at identical velocities into the same test medium you're going to get substantially different penetration results from each bullet. Sectional density is a very poor predictor in this case and is generally unhelpful in predicting terminal performance with most bullets. It still has uses, but IMO there is too much emphasis placed upon s.d. Using my example of 150 grain bullets, I've witnessed poor results with NBTs from a 30/06 on whitetails and I'd use the TSX in a 30/06 for moose without concern. YMMV.
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    Quote Originally Posted by Bighorse View Post
    How far than would that 300 barnes travel before it dropped to that 1800 fps if it leaves the barrel at 2500fps? That would essentially dictate range. Is the Balistic coefficient better for the Nosler Partition or the Barnes X in the 300g .416 bullet? It's hard to find good BC 300g bullets for this gun. .
    Also important is your target species... while a 300gr TSX might have a low SD it is still a physically long bullet and should penetrate very well. As 1 Cor pointed out- with mono construction out of copper (less density than lead) the SD number isn't the only indicator- physical lenght is a stand in for that to a point. Comparing SD for a Nosler Pt and a TSX won't be useful since they vary in construction so much. An Etip and a TSX would be a valid compairson though.

    But even then a shorter cup and core 300gr bullet might have enough penetration for your intended species- even with crappy SD and reduced velocity at extended ranges a .416 should shoot clean through all but the biggest of critters since its designed for the largest game on earth.

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    As long as you are talking 300 yards, more or less, I think it pretty much a mute point - For the most part when you advance beyond 8mm the bullet makers design them with tough hides and larger bones in mind, even the Sierra spitzer boattails which have a long reputation of being "upsettable" at faster than say '06 velocities are tougher, per Sierra technical staff, than the lesser bores and I dare say that the rest will be in unison on that - I doubt you'll find a varmint or even mule deer bullet in .416 and I totally agree with the previous mention about camparing Barnes with a Partition, they're designed to act very differently in their terminal performance (even though the descriptions may suggest otherwise) A "good" comprimise may prove more of a challenge in that larger bore - As for "plotting" your intended bullet's path on paper, get a Nosler #6 manual as it has all sorts of charts and data "what if's" just don't rely on it tooo much, actual trial will often prove the paper data wrong - that .416 bore has always intrigued me ....

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    That information is helpful. So if I read you right, SD is a value that compares bullets of similar construction and at one point was a standard measure to gauge said bullets. Now with differing projectile construction you can gain sufficient terminal peformance from bullets with lower SD and excellent design characteristics. So now were seeing stuff that relates to BC and pentration speed values.

    I wonder how much mystique is tied up in the SD perception of yesterday? As I alluded to in the start, a short range shot from a fast and well constructed bullet is very potent.

    Hodgeman, I think the 300g TSX is right up my alley for this application. If properly loaded I should have a great round for a multitude of hunting and defence situations. I'm gonna try the Nosler Partitions too though, a personal favorite if I can find them in the 300. I think I saw some on cheeper than dirt or Gander mountain once.

    I wonder if my Lil-gun powder, I use for my 41 magnum would be a potential poweder choice for this application? That may burn too fast for shorter barrel or shotgun applications. Honest question.

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    The only 300gr .416 I'm aware of is the Barnes TSX. I think a handful of folks still make a 325 or 350 but the more common weight in this bore is 400 grains, a few companies also make some heavier as well. The bulk of the .416 business is Cape Buffalo and Elephant and even big bears aren't nearly that thick.

    I think there's nothing in AK not suited for the .416/300gr TSX.

    Some sources on the web (use due caution) claim a starting velocity of 2700fps with the 300gr out of the 20" barrel. You should stay above 1800fps to well beyond 300, maybe just to 400yds. I'd take Barnes 1800fps figure with a grain of salt... it might open at 1800 and then again it might not, but at any rate you'll have a very useful cartridge to 300yds.

    Don't know much about Lil Gun but I'd be uninclined to experiement when you're using this much powder....I'd find a recipe and stick with it . You might want to check with Murphy as I believe he's done a fair bit of experimentation with cartridges very similar to the .416 Ruger (if not the actual cartridge). I'd expect Barnes to publish load data shortly as this cartridge gets more popular.

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    Quote Originally Posted by Bighorse View Post
    That information is helpful. So if I read you right, SD is a value that compares bullets of similar construction and at one point was a standard measure to gauge said bullets. Now with differing projectile construction you can gain sufficient terminal peformance from bullets with lower SD and excellent design characteristics. So now were seeing stuff that relates to BC and pentration speed values.
    Sectional density is a numerical expression derived from mass and caliber. For example, all 400 grain .416 caliber bullets have the same s.d. (.330) regardless of their shape, construction or composition. Its purpose was to predict penetration, and you are correct in so far as bullet construction can provide for more penetration even with significantly less mass.

    Quote Originally Posted by Bighorse View Post
    I wonder how much mystique is tied up in the SD perception of yesterday?
    IMO, too much.

    Quote Originally Posted by Bighorse View Post
    Hodgeman, I think the 300g TSX is right up my alley for this application. If properly loaded I should have a great round for a multitude of hunting and defence situations. I'm gonna try the Nosler Partitions too though, a personal favorite if I can find them in the 300. I think I saw some on cheeper than dirt or Gander mountain once.

    I wonder if my Lil-gun powder, I use for my 41 magnum would be a potential poweder choice for this application? That may burn too fast for shorter barrel or shotgun applications. Honest question.
    NPTs only come in 400 grains for the .416. Speer makes a 350 grain Mag-Tip that may be more what you're looking for and Barnes has released a 350 grain Tipped Triple Shock that should have a b.c. over .400.

    I cannot imagine that Lil-Gun is suitable for your .416 Ruger using jacketed bullets. I recommend against trying it. Though I've never loaded for the Ruger I've loaded the .416 RM for years and have had excellent success with IMR 4064 and RL 15; they would undoubtedly be a good place to start in your .416 Ruger.
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    I agree that LilGun is not the powder for that 416 at all - That Barnes TTSX in 416 might be just the ticket for that "comprimise" bullet as anytime you can past .400 in BC you are in what "some" would call long range territory (not THAT long range territory)

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    Quote Originally Posted by hodgeman View Post
    Sectional Density is calculated with the following formula-- SD= (mass)/ (area).

    In bullets the bore is a fixed size so all bullets of the same caliber have the same cross sectional area, the only variable is mass. On bullets of similar construction a heavier bullet is a longer bullet.

    With a uniform amount of force, a long skinny projectile will penetrate a medium better than a bigger diameter but shorter one. Ie. a long, heavy for caliber rifle bullet will outpenetrate a musket ball or pistol bullet given equal weight and velocity.

    The SD number published is useful for comparing bullet profiles of varying calibers. As rule of thumb- a bullet of high sectional density with outpenetrate one of low sectional density.

    The really successful cartridges of years gone by all featured long, heavy bullets nearly across the board despite some pretty meager velocity numbers...that should tell you something.

    I don't get wrapped around the axle about energy numbers....you can get some impressive numbers with light bullets at high velocity but the low sectional density will limit penetration if bullet construction doesn't limit it even more.
    Actually its the weight in pounds divided by the square of the diameter SD=w/d*d 400 grain .416 bullet

    400/7000 (grains in a pound) = .05714286 .416*.416=.173056 .05714286/.173056=.33019866 SD=330


    But spot on with everything else.

    And I'd say energy transfer has nothing to do with wounding and it is wounding that causes blood to leak out.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Quote Originally Posted by Bighorse View Post
    I wonder if my Lil-gun powder, I use for my 41 magnum would be a potential poweder choice for this application? That may burn too fast for shorter barrel or shotgun applications. Honest question.
    Absolutely not. Get some H4895.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Certainly bullet shape and construction as well as velocity being factors in penetration. All those things being equal....SD will determine the penetration based on laws of physics. For this reason; Any .416 diameter bullet with higher SD will also be heavier than a lower SD of same composition and shape.....Momentum is Mass * Velocity.....Momentum determines penetration....considering same composition, construction and shape. Don't get confused here, folks. This is why SD was linked to penetration....back when all bullets were the same shape and material.

    Now we can argue that any bullet of a certain design, composition and construction may out penetrate another and that might be fun.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Thanks Murphy. I think the 350 g tipped tsx worth a look. I appreciate your imput as I work up this gun as my main solo backcountry weapon.
    While I use a 25-06 often, I realize that in defensive situations a more powerful round will be more optimal. Even goats could use a bit more medicine when I want them down now.

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    BigHorse if you have the leg bones a good seeing test would be to shoot the bone with each gun. My experance has shown the little fast will pin hole the bone and big/slow will break it in half
    Now left only to be a turd in the forrest and the circle will be complete.Use me as I have used you

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    I would bet that 350 grains of .416 anything would be something to be reckoned with - That's not your "everyday" hole size !

    I am being "haunted" by the urges to do a .416 WSM ... can't shake it - As soon as $$ allows it gonna happen

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    Maybe BRWNR will jump in this thread. I think he has a .416 Rem. that he uses on his guided hunts and that 350 grain Barnes X may be what he is shooting. If it is then he will have some practical field experience to share. I do know one guy that has been shooting a wildcat .416 for over 20 years and uses 350 grain Barnes X bullets. I think it is about all he uses for his moose and bear hunts. He considers it the "Hammer of Thor". Like others have indicated, sectional density is an indicator of possible penetration, if all things are equal. For sure the old Nosler Partition started to change our thinking on that many years ago. The Barnes X and a few other bullets because of their construction have allowed the use of lighter bullets in many calibers. I pretty much use a middle of the road bullet weight for a caliber. 180 grains for the 30-06, 250's in the .338, etc. If I had a.416 I would start with the 350 grain Barnes X and hope it shot well.

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