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SD Ammo, SD, and what it means and why

This is a discussion on SD Ammo, SD, and what it means and why within the Defensive Ammunition & Ballistics forums, part of the Defensive Carry Discussions category; "This is where less weight actually becomes more beneficial. It requires less energy to expand. Simple physics." That law of physics could use some explanation. ...

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  1. #46
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    "This is where less weight actually becomes more beneficial. It requires less energy to expand. Simple physics."


    That law of physics could use some explanation.

    The various features that promote bullet expansion will behave the same way whether the bullet is at the light end of the weight range for a given cartridge or the heavy end. Weight in and of itself isn't what retards bullet expansion but rather materials and construction of the projectile along with insufficient velocity.

    With nearly all of today's mostly watered down loadings, the .38 Special snub isn't exactly going to set the woods on fire velocity-wise no matter how light the bullet is. Buffalo Bore, and a very few other selections, or else the handload, extract the highest performance from the .38 Special. With the snub, I particularly want to insure penetration. The 158 grain semi-wadcutter offers that and chops a dandy hole while doing it. Works great on critters and varmints.

    For myself, I'm not using any sort of piddly lightweight bullets in a .38 Special. If I wanted to shoot lightweight bullets I'd select the more feeble .380.

    Same for 9mm. I prefer bullets from the heavier end of the range of weights available.

    Don't have a .40 but would use 180 grain bullets in it if I had one to carry. I confess to mostly carrying 230 jacketed round nose in the .45 ACP and always have.
    Charter Member of the DC .41 LC Society

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  2. #47
    Member Array Eaglebeak's Avatar
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    Wow - I came back to this thread to thank bmcgilvray for clearing up my terrible bit of misinformed ignorance that I mistakenly purveyed about the weapon used by "Son of Sam" in a very poor example only related to get a point across about high velocity and over-penetration often being a bad thing in close-quarter defensive handgun use. But it looks like glockman10mm's original words of very true wisdom (regardless of what some may think) has started a great debate over light weight bullets at high velocity being equal to (or better than) heavier bullets at lower velocity because muzzle energy between the two can be relatively equal.

    First I must apologize to everyone over my "bovine exhaust" of thinking the .44 Special actually used by Son of Sam was a .44 Mag - my bad - duh. I was using the much higher velocity and muzzle energy of the .44mag to explain where higher velocity of the same relative caliber and bullet weight can quickly pass through a human without time for the bullet to expand properly and not expending nearly as much of its muzzle energy on the victim as a slower moving .45ACP that would most likely stop inside the victim and actually apply more energy (shock-power) to the body than the small amount that was expended on the body by the much higher velocity bullet that quickly exited and still retained the greatest part of its original energy. Embarrassed am I since a .44 Special is just a tad under the .45ACP in all aspects. After more research (from humiliation), I found that Son of Sam was using standard FMJ ball ammo and not hollow-points as I was also under "bovine exhaust" misinformation.

    However, sometimes good information can arise from a pile of bad stinky misinformation because the basic premise I was trying to relate about over-penetration is still valid. Since SoS' .44 Special round isn't far enough away in ballastics parameters, bullet weight, bullet CSD, bullet SD, and velocity from a .45ACP round to make any appreciable difference (for sake of argument), the stated opinion of all the medical professionals involved is also a truth. The general consensus of opinion to explain why the death rate of SoS's victims was a bit less than 50% (when all were shot multiple times at point-blank range of only a few feet) was that most of the bullets passed completely through the body without expending much of their muzzle energy as lethal "shock-force" (or blunt trauma); therefore, the "lucky" victims were fortunate that the holes punched through them didn't hit any major arteries, heart, or brain that allowed them to eventually recover from their wounds. If SoS had been using rapidly expanding ammunition (soft-nose or hollow-points) it was agreed the death rate of his victims would have been much higher because they would have stopped most of the bullets fired and absorbed enough blunt-force trauma (adding to the physical shock of the wound itself) to kill most of them on the spot.

    One never knows if a bullet will hit home in a totally unobstructed area of soft tissue and over-penetrate to a quick exit or if it might encounter heavy clothing, belt buckle, neck mediallion or a Zippo to fragment and/or under-penetrate; thus my personal reasoning for having a self-defensive magazine loaded with alternating (heavy-weight) ball and hollow-point ammunition for a "left-jab/right-cross" combination punch - if one don't work, maybe the other will.

    Regarding the discussion or debate of "light bullet at high velocity" versus "heavy bullet at lower velocity" - well, opinions are like something everyone else has, so here's my humble a$$h...... er, opinion for what it's worth. Even though I'm getting far away from a defensive close-range handgun, the comparison that I've personally witnessed in the same aspects of this debate with combat rifles still applies. People and scientists can argue the myriad of physics principles involved from now on and devote countless hours of shooting gel blocks to formulate opinions; but (like many of my old warrior peers still walking around), I base my humble theories on what I've seen and experienced in reality - not the textbook or computer model. Many years ago during a very dark time in the earth's anus, I was able to gain first hand experience in the effectiveness of a small caliber, very high velocity, lightweight bullet versus a larger caliber, lower velocity, heavier bullet while hunting two-legged "big game" (while also being stalked and hunted by my quarry) - hey, it's cool - no hunting licence required, open season all the time, and no bag limit. The only common ground that both hunting parties shared was the use of FMJ non-expanding bullets (so more possible disagreement becomes fertile on differences between the myriad of expanding bullet types of the same weight and caliber - geeeezzzze - no win situation)......

    My jungle-hunting party was shooting high-velocity .22's with extremely light bullets while the big game we hunted was shooting much lower velocity .30 calibers with almost three times the bullet weight back at us just to keep the hunt interesting and exciting for all parties concerned. Even though both types of weapons were very close in their respective muzzle energy, we were easily able to compare the damage each weapon inflicted on the respective game animal and the very different abilities that each respective round had in maintaining accuracy when travelling through brush, vines, thick grass, and other game animals. For the sake of ballastics comparison between the two very diverse rounds:
    M-16: .223 caliber (5.56 x 45mm) / Bullet Weight = 55 grains / Muzzle Velocity = 3250 fps / Muzzle Energy = 1289 ft/lbs
    AK-47: .30 caliber (7.62 x 39mm) / Bullet Weight = 124 grains / Muzzle Velocity = 2350 fps / Muzzle Energy = 1495 ft/lbs

    Try to imagine the thrill of the hunt (in dense jungle with an average reasonable visibility range of 2 or 3 meters) when you suddenly spot (or are spotted) by more game animals than you have rounds in your magazine - whoopee!! let the fun begin. Adding to the excitement of the hunting experience is the fact that most of your high-velocity shots with popcorn-weight bullets are being deflected way off target by the slightest encounter with a leaf or bug that may lie beween you and your quarry (obscured behind said dense jungle growth) while your rapid aiming/sighting ability on numerous members of the flock is frequently challenged by having to wipe pieces of a hunting companion from your eyes while listening to those pesky little "jungle bugs" making a loud snapping sound as they (hopefully) whizz by your head because those nasty little bugs are much heavier, travelling a lot slower, and have a very uncomfortable tendency to stay on target through the scenic flora they travel in your direction. After a fast and furious hunting experience, those still able to stand can't help but inspect what's left of game animals on both sides that will never stand again and note the extremely different charastics of damage inflicted by each particular round. While this "field method" of assessing the effectiveness of combined physics applications isn't nearly as scientific as the printout of a computer model or examination of a gel block, it's still a fairly reliable "real world" indicator.

    Funny how I suddenly feel a bit of relief - I guess they're right about getting bad memories out of hiding is good for the soul. Back to the debate of high-velocity popcorn versus low-velocity rocks, I can't tell you how many times I've risked "friendly fire" (because of the distinctly different sounds they generate) by slinging a freakin' ineffective, undependable POS-16 and continuing the hunt with a retrieved '47 before wrapping it around a tree at the end of the hunt. I know I risk more blasphemy charges for bad-mouthing both the M-16 and the .223 round than I'd get from raking a Harley Davidson, but they are both an ineffective and undependable piece of crap in all but the most perfect of situations. The 16 is sweet and deadly accurate when kept perfectly clean, and the high-velocity .223 popcorn bullet is very effective when it can travel completely unobstructed across a 300 meter span of sand, prairie or pack ice to whack a pop-up target, penguin, prairie dog, or bipedal camel tick; but I'd rather have a sharp stick or hand full of rocks than either of the two in obstructed areas or adverse conditions.

    Folks will just have to find it in their hearts to forgive a crusty old curmudgeon who pretty much ignores info-videos by "professional experts", YouTube demos, computer-generated ballistics data, gel-block tests, and exaggerated sales hype because I've personally assessed the major differences in damage inflicted on two-legged game (and effectiveness through obstructed areas) by lightweight/small caliber/high-velocity projectiles compared to the overall superiority of heavier/larger caliber/lower-velocity projectiles.

    PS, one could leave a beloved 16 laying in the middle of a jungle trail and find it still laying there a week later - albiet kicked aside the trail to get it out of the way. In spite of having easy access to tons of captured ammo, our game animals knew what was best and would only consider retrieving a 16 if they needed a jack handle or for occasional use as a "game call".

  3. #48
    Senior Member Array SFury's Avatar
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    A bullet of X weight in M caliber requires a certain amount of energy to achieve expansion.

    I should have mentioned this last night, but look at the barrel in your gun. You'll notice some grooves. Those rifling grooves add spin, and spin adds energy to the projectile assuming it's an optimal twist rate. The longer the barrel the more that twist rate matters.

    People need to not make blind statements. That's all I'm saying here. Not all heavy loads are equal. They will not all expand from all guns equally. It's just as important to choose a round that can expand effectively from the firearm(s) you are using. Expansion equates to more reliable stopping power.

    Choosing the correct ammunition means understanding what it was designed for. On that we should all agree. Look at the different things that can be done for the same weight rounds from the same company. Different rounds for different jobs are commonplace.

    The articles I've read, the shows I've watched, that have compared various rounds through various handguns to see what effective loads work best in a given gun show that in some calibers, and in some guns, lighter is better. Snubbies in the .357 mag have been mentioned in various articles I've read as to being equally effective, if not more so, using the heaviest .38 +P loads over the lightest .357 loads. Here is the first article I could find online this morning. It agrees with everything being said here that in most cases heavier is better. Just, not in all cases. There are only two absolutes in life. Death and taxes.

    It's up to those who buy their own firearms to make the best informed choice they can make. With tiny pocket guns being more prevalent, buying the right ammo doesn't mean the older blanket statements are correct as often as they used to be.

  4. #49
    VIP Member Array glockman10mm's Avatar
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    "and spin ads energy to the projectile"

    Well, what's left to say after that?
    Hoganbeg likes this.
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  5. #50
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    Just your tagline, Gman.

    Just your tagline.

    There are no dangerous weapons; there are only dangerous men.--RAH

    ...man fights with his mind; the weapons are incidental.--Jeff Cooper


    There is a reason they try and make small bullets act like big bullets--Glockmann10mm

  6. #51
    VIP Member Array 10thmtn's Avatar
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    Eaglebeak - Thanks for your service, and your insight. While I have a 5.56 Mini 14, I much prefer the heavier .30-30 out of my old-tech Marlin 336 lever gun, for all the reasons you gave. I had an M16 in the Army, and was never impressed by it - all the AR lovers can now start wailing and gnashing their teeth, but it is what it is.

    SFury - Rifling does NOT add energy to a bullet. It actually causes friction, which causes a bullet to slow down. This is the reason the latest tank cannons (120 mm) are smooth bores. The shells are stabilized by fins, and the tanks use fancy ballistic computers to help ensure hits. The smooth bore guns give the maximum velocity to the sabot armor-piercing rounds, which use simple momentum to punch through armor. (look up "APFSDS" if you want to know more)

    As a general comment - if you are worried about expansion, you do need to check into the performance of your chosen JHP through your barrel length. Barrel length affects velocity, and JHPs are designed to work within a certain velocity "window." Too fast, and the JHP may over-expand and fragment, resulting in shallow penetration (this was an issue with some light JHPs fired through the longer barrel of 9mm sub-guns). Too slow, and they might not expand properly, or at all.

    However, I'd rather take a heavier bullet that might not expand, but that still penetrates deeply, to a lighter one that may not penetrate deeply enough, especially after hitting an intermediate barrier (barriers are not a concern for me off duty; but it is a concern on duty). Off duty, I have no issue with using 124 gr 9mm, but on duty, I'm in the process of switching to 147 gr.
    The more good folks carry guns, the fewer shots the crazies can get off.
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  7. #52
    VIP Member Array glockman10mm's Avatar
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    10thmtn, thanks for that info. I'm still recovering.
    Ignorance is a long way from stupid, but left unchecked, can get there real fast.

  8. #53
    OD*
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    I'm still a believer in John "Pondoro" Taylor's Knock Out (TKO) Scale for measuring the power of calibers.
    "The pistol, learn it well, carry it always ..." ~ Jeff Cooper

    "Terrorists: They hated you yesterday, they hate you today, and they will hate you tomorrow. End the cycle of hatred, don’t give them a tomorrow."

  9. #54
    OD*
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    Gman, John Linebaugh has some good reading on heavyweights
    Linebaugh's Custom Sixguns - Heavyweight Bullets

    ETA: Some older penetration tests that were conducted at a Linebaugh Seminar.
    http://www.handloads.com/misc/lineba...tion.tests.asp
    "The pistol, learn it well, carry it always ..." ~ Jeff Cooper

    "Terrorists: They hated you yesterday, they hate you today, and they will hate you tomorrow. End the cycle of hatred, don’t give them a tomorrow."

  10. #55
    VIP Member Array glockman10mm's Avatar
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    Quote Originally Posted by OD* View Post
    Gman, John Linebaugh has some good reading on heavyweights
    Linebaugh's Custom Sixguns - Heavyweight Bullets
    Thanks for that. I am familiar with Johns work, and credit his R&D in the field in large part as my turning to the use of heavier bullets.
    Ignorance is a long way from stupid, but left unchecked, can get there real fast.

  11. #56
    VIP Member Array 10thmtn's Avatar
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    Quote Originally Posted by shockwave View Post
    F = m * a

    Basic physics teaches that force equals mass times acceleration. Same as e = mc2. The variables can be set to equal desired outcomes.

    A faster lighter bullet will carry the same force as a slower, heavier one.

    I don't pay much attention to this argument. For me, it's all about measured, proven expansion. The Corbon DPX round consistently produces the perfect, star-shaped ragged petal projectile I look for in a SD cartridge.

    The relevant physics are really:

    momentum = mass x velocity; and, kinetic energy = 1/2 mass x velocity (squared)

    E=MC^2 is Einstein's Theory of Relativity. It explains how you can power a naval vessel for years with a few pounds of radioactive material, but has little to do with ballistics.

    Also - Lots of comments about "energy transfer" and the like. Most of the commentary from medical professionals (that I've read) who deal with gunshot wounds indicates that, with respect to handgun wound tracks, there is virtually no difference between JHPs and FMJ...nor between the various calibers used. I'm not at all convinced that JHPs have some greatly enhanced "stopping power" versus FMJ. Some benefit, yes - due to their slightly larger diameter, but not as much as many seem to suppose. The greatest benefit, IMHO, is in limiting the risk of over-penetration.

    I'll defer to those who hunt with service caliber handguns (gman), if they know different than me - I just know what I've read from the medical folks who deal with this daily in the ER.
    The more good folks carry guns, the fewer shots the crazies can get off.
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  12. #57
    Senior Member Array AZ Hawk's Avatar
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    Quote Originally Posted by glockman10mm View Post
    "and spin ads energy to the projectile"

    Well, what's left to say after that?
    I was thinking exactly the same thing.
    Move. Shoot. Survive. ― The "Unofficial" Suarez International Doctrine

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  13. #58
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    Quote Originally Posted by RKM View Post
    I've mentioned before in the other thread that I too like heavier bullets rather than light bullets. However, I carry 185gr DPX, and that's my only exception :) Though, velocity I think is also an important factor. It's clear when you take a 150gr .30 caliber bullet at 2700fps against a 230gr .45 caliber bullet at 850fps. We all know which one wins. Of course, this comparison is a bit much, but it shows that velocity means much more.

    Comparing a 230gr .45 caliber bullet at 850fps vs. a 185gr .45 caliber bullet at 1000fps, I can see the advantages of a heavier bullet. Though, I don't believe energy rating in handgun calibers matter as much as they do in rifle calibers, but usually a lighter/faster moving projectile creates more energy on target in the same caliber. Again, I don't think this really matters in handgun calibers.

    But anyway, we need to remember to rely on the infamous shot placement. It's important to have a good caliber, but it's easy to get caught up miniscule differences in ballistics results that matter very little in real life when shot placement is what matters most.

    That's my "far from expert" opinion. And that's all it is.
    Very reasonable. Here's another way to look at it.

    Consider two rounds loaded with identical 158 gr projectiles, but with different powder loads, so that one has a muzzle velocity of 1500 fps and the other 1000 fps. I think we would all agree that a 158gr bullet at 1500 fps is more powerful than the same 158gr bullet at 1000 fps. Now, keeping velocity constant, consider the effect of slight reductions in bullet weight of the faster bullet. That reduces the advantage of the faster bullet, but if the reduction is slight, the faster but smaller bullet is still more powerful. If you continue reducing the weight of the faster bullet, still keeping velocity constant, at some point you will reach a weight at which you are indifferent between the two rounds. This discussion really is about where that point of indifference is. It's probably different for different targets, and probably also for different shooters. But I don't think anyone can rationally show that there isn't a point at which the effectiveness of the two bullets is equivalent for a given application.

  14. #59
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    So a mosquito leg thrown at 900,000 feet-per-second is optimal.
    Charter Member of the DC .41 LC Society

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    Theodore Roosevelt, The Wilderness Hunter, 1893

  15. #60
    Senior Member Array AZ Hawk's Avatar
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    Quote Originally Posted by bmcgilvray View Post
    So a mosquito leg thrown at 900,000 feet-per-second is optimal.
    Haha!
    Move. Shoot. Survive. ― The "Unofficial" Suarez International Doctrine

    “The real man smiles in trouble, gathers strength from distress and grows brave by reflection.” ― Thomas Paine

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