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Thread: penetration velocity

  1. #1

    Default penetration velocity

    I was recently looking at someone's ballistics test online, and noticed that among identical bullets, the slower ones penetrated deeper! (like 2100 vs. 2400 fps). And I've heard that the old-school african hunters viewed 2200 fps as ideal penetration velocity. Also, Garrett Cartridges claims that deepest penetration (at least in .458) occurs between 1300-1600 fps (and they're talking about NON-expanding bullets).
    What do you all make of it? And by the way, I'd be interested if anyone has any such numbers in relation to 9.3mm

  2. #2

    Default

    Sure lines up with what I've seen on game and in test media. I've shot a lot of game with cast bullets from handguns and rifles in those velocity ranges, and bullets are darned hard to recover short of searching the terrain with a metal detector. Higher velocities and especially bullet deformation sure disrupt a lot more tissue over a shorter span, but also seem to cut down on penetration.

    I don't have anything specific to 9.3, but have shot a fair bit with the RCBS 35 cal 200gn FN and an assortment of 200gn jacketed softpoints from the same guns at the same velocities. I've recovered a lot of the jacketed ones, but none of the cast.

  3. #3
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    The majority of hard cast bullets used in firearms to take big game are very similar to using solid bullets. They don't expand and therefore do not slow down as quickly. But on the other hand there are bullets like the Barnes X or Swift A-Frame that only expand to a certain diameter but will still completely penetrate an animal. These bullets like the Barnes and Swift's can be driven to very fast velocities and still penetrate completely. I have recovered both hard cast bullets and bullets like the Barnes X and Swift A-Frames within animals. Shoot a Moose with a hard cast bullet with a Texas heart shot and you will recover that bullet within the animal. Shoot a moose through the lungs with a hard cast bullet and you will more than likely not recover that bullet. Use a Barnes X bullet or a Swift A-Frame in the same fashion and you will not recover it on the lung shot but you will on the Texas heart shot.


    Joyce Hornady loved getting calls from hunters stating that his bullets failed on big game after being recovered from within an animal. He used to ask the person calling at what point in the animals death did the bullet fail.

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    Alleninalaska is correct about A-Frame, and Barnes bullets such as the Triple Shock, and X. One can also add the Fail Safe, North-fork bullets to this group plus others I have not mentioned.

    Slower velocity helps with penetration because higher velocity makes the bullet expand sooner. However, controlled-expansion bullets such as those mentioned above are designed to expand and still penetrate. This is achieved by controlling the degree of expansion in relation to bullet speed. Even when driven extremely fast, these bullets still penetrate as designed. They just shed the perimeter of the area that has expanded, but the rest of the bullet keeps moving forward. For example, the Triple Shock, or the FS bullets may shed some of the petals, but the cylinder-shape body plows through. Also, the petals create additional wound channels if they separate from the bullet.

    The A-Frame, if driven too fast, may shed some lead from the "mushroom's" perimeter, but even so it's designed to retain around 80%+ of it's weight. Like the others mentioned, most of the bullet plows through.

    A Partition is softer than the ones mentioned above, but it still is a controlled-expansion bullet. It just sheds more weight than the others. If driven very fast it may shed most of the lead in front, but the base plows through. While the A-Frame and the other bullets above may retain from 80 to 90%+ of their weight when driven fast, the Partition may retain around 60%.

    The Partition Gold is designed to retain much more weight than the Partition, and so the Partition designed for use in Lazzeroni rifles.
    ----
    Other than that, lets say that you have two 250-grain partition bullets for your rifle, one loaded to produce a safe but slower velocity, and the other to produce a still safe but faster velocity. In this case the slower one has the potential to penetrate deeper. But in cases where you may have to take a longer shot on game, the faster bullet will still hit the mark at a slower speed. See...bullet manufacturers have already done all the homework for you.

  5. #5
    Moderator Paul H's Avatar
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    Bullet construction has the biggest effect on penetration, and over which velocities a bullet penetrates the deepest. Barrel twist has also been found to have an effect on penetration.

    With a conventional cup/core lead/copper bullet they do tend to penetrate deepest around 2000-2400 fps, and much past 2700-2800 fps they tend to really come apart. With a bonded core bullet, or a mono-metal hollowpoint aka Barnes X, the bullets penetrate deeper at higher velocities.

    With cast bullets, they start to get damaged at higher velocities, ie around 2000 fps, so give up some penetration.

    If you look at the new mono-metal flat faced solids, some of them get incredible penetration at 2500 fps.

    Penetration isn't everyting in terminal balistics, and giving up wound diameter for penetration can be a bad tradeoff. Also some deep penetration rounds seem more impressive than they are when you ignore wound dia.

    For 9.3mm, I'd say if you went with a barnes triple shock in 250 gr, you'll get penetration on par if not better than a cup core 286 gr, and a large dia wound.

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    Default Penetration vs Velocity...

    BB, Allen, Ray and Paul,

    You guys have it covered. I would say I agree with all this. Only to add nothing is 100% predictable when hunting, and we can never be sure of what will happen to a bullet but this is certainly a very good general synopsis for penetration vs velocity. It's always a compromise when selecting a bullet. I think matching bullet construction to velocity is the best approach.

    Is a 260 grain cast bullet at 1800 fps from my Marlin model 93, 38-55 enough gun for brown bear?

    Thanks guys,
    Murphy
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  7. #7

    Default 38.55

    From 44 mag range or a little over I would think it would be good.
    Now for you - what would be the outside range for 44Mag?
    Mike :-)
    Mike
    www.alaskaatvclub.org
    There is a faster way off the mountain, might hurt a little though.

  8. #8

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    In regards to bullet penetration versus velocity, a USDA Forest Service study on bullet performance demonstrates that a lower velocity will equate to deeper penetration and increases retained bullet weight to a point. It isnt uniformly true, and I am sure more can be done on the subject, but it is still a facinating read.


    http://www.fs.fed.us/pnw/pubs/gtr152.pdf

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    Quote Originally Posted by Murphy View Post

    Is a 260 grain cast bullet at 1800 fps from my Marlin model 93, 38-55 enough gun for brown bear?

    Thanks guys,
    Murphy

    Murphy I would not hesitate too use it at 1800 FPS and under 75 yards. My little 375 Winchester would probably only launch that same bullet at about 2,000 FPS and I would use it in a heart beat if it was what I had in my hand at the time.

  10. #10
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    Smile

    Quote Originally Posted by Mike Echo View Post
    From 44 mag range or a little over I would think it would be good.
    Now for you - what would be the outside range for 44Mag?
    Mike :-)
    Mike,

    With a good revolver in 44 Mag I'm only good to about 75 yds for dependable hits. I could stretch that in good light but with irons and my eyes, that's about it. With the Lyman #66 aperature sight on the Marlin 93, I could probably hit out to about 150 but thats stretching the 38-55.

    The range at which I can consistantly shoot 6" groups under all conditions, that's my range for a hunting handgun. Under ideal conditions, I'm still a pretty good shot. I almost never shoot to the limit of my equipment, I have a big reserve in there for safety.

    Good shootin'.

    Murphy
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  11. #11

    Default and.....

    Who is going to uncover the mysteries of the relationship between bullet velocity when it exits the animal and the amount of energy transfer to the animal....
    Work-energy theorem anyone??????

  12. #12
    New member George's Avatar
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    Default energy

    AK Steve, Another way to think about this....my brain is tired right now but you bring up a food-for-thought topic or question... % of or amount of a bullet's total energy used up on air, soil, brush, tree trunks, etc..... after it has passed through an animal? Related topic- hydrostatic shock (compression wave) tissue destruction surrounding the bullet as it passes through tissue... a real thing, proportional to velocity and related to bullet size and shape (or changing shape).

  13. #13

    Default old dynamics text

    Ahhhh, I think this is pretty much straight forward work energy thereom. The work down on an object is equal to the net change in kinetic energy. I believe the rigorous proof is via Newton's Second Law.
    Have we just discovered a major flaw in the body of knowledge related to the so called "knock-down power" of a cartridge.
    This might be worth a new thread....

  14. #14

    Default Velocity vs Penetration

    The accepted rule assuming all things being equal, a slower projectile will normally have greater penetration than a higher velocity simply because at higher velocities the bullet generally expands causing more resistance which limits penetration, again a monolithic solid is a different story since there will be no expansion however there is a point where nothing is gained from more FPS

  15. #15

    Default Penetration vs. Velocity

    From my library of scanned stuff I submit this graph:



    Only thing I have to add is that penetration and expansion are mutually exclusive. You can't really optimize both - there are always trade offs.

    Me, I like 2,700 to 2,800 fps MV tops for all my Big Game applications.

    MM

  16. #16
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    Default

    Excellent thread! There are a few comments I would like to add. As basics: Penetaration is a product of Sectional Density and Velocity. Tissue damage is a product of Velocity and Meplat Area (expanded or not expanded)!
    However, in bullet above .50 caliber, there is a compromise. If a very large diameter bullet has a meplat about 75%, the hunter will get more than adequate penetration and tissue damage! An outatanding example of this was the famous Paradox guns use in Africa and India. A .730"-730 gr hard cast heat treated bullet, with a velocity between 1200'/" and 1400'/" is a devastating load! Penetration is deep even in tough tissue and large bones! The recoil of the 1200'/" (which happens to be the velocity of the Cordite Paradox 12 bore) makes the gun more controlable than the 1400'/".......and gives up only a few inches penetration. It is most important that the hard cast bullet is not brittle! Leave out the tin and use a lead/antimony mix! This type of load is perfect for shots 100 yards, and under, in heavy brush and against dangerous game in close! y really is simple.....if this type of load work in Africa/India on some rather dangerous game, it will still work today! Regards, James

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