HP expansion/balistics question(s)

Discussion in 'Ammunition & Reloading' started by BeyondTheBox, Oct 3, 2012.

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  1. BeyondTheBox

    BeyondTheBox New Member

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    So I've got a 9mm two shot derringer I use as a backup carry piece. I've been told that, due to the short barrel length, there wouldn't be enough velocity to cause an HP to expand from such a handgun.

    My main concern, when considering defensive firearms, is safety. Not for myself, but, rather, for those around and in possible danger of an over-penetrating round. So I've started carrying lower calibers, but I do see the possibility of a need, in a unique occasion, in which some hopped up druggie might require a more persuasive nudge, thus the backup.

    My question is, if the velocity from my derringer is so much less, should I even bother worrying about over-penetration? Or how can I test this myself without paying a crazy price for balistic gel? Not sure what it costs, but guessing it's up there.

    Also, isn't the point of an HP to reduce chance of over-penetration? Is what causes the round to open the resistence received from its coursing through the air or the contact with its target? If it's the air, then wouldn't it be reasonable to assume that the impact with a body too could create that necessary resistence, allowing it to open and still serve its purpose, regardless of barrel length and/or velocity? If not then I understand.

    I'll fully admit it, I'm very inexperienced and unknowledgable when it comes to balistics and all this, hence my being here. How I'e come to my theory above is simply through a novices attempt at logical thinking. Hahaha

    Speak some knowledge at me; take me to school fellas!!!

    Thanks inadvance!
     
  2. JTJ

    JTJ Well-Known Member Supporter

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    1 gallon water jugs in a tight line (touching) will give you an approximation of expansion and penetration. A 1 gallon water jug is about 5" across. 2 jugs is roughly equivalent to 5" of penetration. 4 jugs = 10". Hang a couple of layers of cloth in front of the 1st jug.
    http://www.theboxotruth.com/
     

  3. BeyondTheBox

    BeyondTheBox New Member

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    Ahhh, to simulate a clothed attacker. Good advice/thought. Thanks man. Can I assume milk jugs refilled will do?
     
  4. CHLChris

    CHLChris New Member

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    Milk jugs is exactly what he meant. Another way would be to borrow someone's chronograph, if possible. Then check velocity against what the box says it should be out of a normal barrel. A LOT less and you'd probably be able to bet on lack of penetration.

    I would skip all of that, myself. Just get a HP that has a polymer insert to aid with appropriate penetration before it expands, if it expands at all. I'm talking about Hornady Critical Defense/Duty or their Zombie Max (exactly the same thing, but green tip.
     
  5. BeyondTheBox

    BeyondTheBox New Member

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    Great ideas, I love it.

    One reason I bought this little thing was because I knew it would fire any round that fit in the barrel. With no ramp or magazine there's no feeding to worry about! Figured it would eliminate any possibility of pickiness with ammo, didn't figure on it having an issue with actually expanding. Hahaha

    Thanks a million for the tips and tricks guys. Solid and very helpful info here!
     
  6. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

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    I believer Speer makes a special load for short barrels. I know they do in .40.
     
  7. SSGN_Doc

    SSGN_Doc Well-Known Member

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    And just to help answer you questiona bout the mechanism of action that causes HP bullets to expand:

    It is largely a function of hydraulics. Liquids don't compress so whe a HP bullet gets into flesh the water in the tissue cells gets into the cavity of the bullet and pushes outward on the core and jacket and cause it to bend and tear and in some case to fragment. Bullets are designed for caliber load by material selection and jacket tickness in areas to help ensure expansion will happen is a certain velocity range so that bullets retain weight and don't fragment like they would if they went too fast. If the bullets are drivven to slow they may not generate the hydraulic force needed to get reliable expansion. This is also why bullets are often tested with denim in front of testing media as well, because if the hollow point is clogged on it's way into the body there my not be enough fluid and hydraulic force to get the bullet to expand reliably either.
     
  8. BeyondTheBox

    BeyondTheBox New Member

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    Awesome explanation doc. Thanks for that.
     
  9. BeyondTheBox

    BeyondTheBox New Member

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    Okay, good tip man, I'll look into that some more, thanks.
     
  10. BeyondTheBox

    BeyondTheBox New Member

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    So doing this jug test, I assume I'd stand the standard 10ft from target when firing. Should I place something solid behind to catch in case it goes straight through, or just a second jug good enough?
     
  11. SSGN_Doc

    SSGN_Doc Well-Known Member

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    What rounds are you testing? If it is a pretty penatrative round I would do lots of jugs and I have used phone books duct taped together as good back stops. Two or three large city phone book thicknesses will stop most handgun rounds.
     
  12. BeyondTheBox

    BeyondTheBox New Member

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    Exactly what I was thinking, I get 'em weekly around here. Thanks for confirm.
     
  13. SSGN_Doc

    SSGN_Doc Well-Known Member

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    OK I read the original post. Yeah, I'd wo with 4 milk jugs. If some of the bullet energy does not get used in expansion you may actually get more penetration. 9mm can penetrate pretty well.
     
  14. armsmaster270

    armsmaster270 New Member

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    Here is the info on the Speer Gold Dot 9mm Air Marshals use Gold Dot 357Sig ammo on duty last time I checked.


    Gold Dot Short Barrel Personal Protection - 9mm Luger +P

    Part Number 23611

    Cartridge------ Bullet Wt.----Bullet Type Box Count Bullet Coefficient
    9mm Luger +P..... 124........... GDHP-SB.... 20...........0.134

    Velocity(in feet per second)...........Energy (in foot pounds)
    Muzzle....... 50 yards......100 yards..Muzzle........50 yards....100 yards
    1150........... 1039..........963..........364............297...........255

    Trajectory if sighted at 25 yards Test Barrel Length in inches 3.5 Usage
    25 yards.....50 yards......75 yards......100 yards 1
    0.0.........-0.9..............-3.9............-9.0



    Usage Key: 1 = Personal Protection | 2 = Training | 3 = Hunting
     
    Last edited: Oct 4, 2012
  15. BeyondTheBox

    BeyondTheBox New Member

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    While I like the idea of +P rounds, in general, this Cobra is made of Zamak and is not rated capable of anything more than standard pressure ammunition.

    That brings up another question. What makes a bullet +P vs standard? Is it the grain weight/count? My father shoots Federal Hydroshock in his 9mm and their 124gr just like the +P Speer listed above.

    Edit: okay I realize it has nothing to do with the grains because there's stamdard pressure 115 & 124 in 9mm. I'm very confused on it, but as long as I read the box and make sure I getvstandard pressure rounds I'll be fine.

    First I'll try those Hornady Critical Defense FTX 115gr, then my pops' Federal Hydra Shok 124gr. See if either performs better or at all and go from there.
     
    Last edited: Oct 4, 2012
  16. BeyondTheBox

    BeyondTheBox New Member

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    Actually, that brings up another question. Would the grains make a difference in the expansion?
     
  17. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

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    Perhaps. A heavier bullet is generally slower. Speed gives the fluid hydraulics the ability to peel open the bullet. Less speed, less expansion pressure.

    BUT, ammo makers have learned a bunch over the last 20 years. They design different hollow point shapes, sizes and volumes for different expected impact velocities. They use jacket scoring in differing numbers, depths and lengths to control the expansion.
     
  18. BeyondTheBox

    BeyondTheBox New Member

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    That's what I was thinking. Hmmm Okay, well I'll be trying a few different types just to see what I can determine. Hopefully I'll find that at least one expands!

    Though it'll be fun testing them all no matter the outcome. I've got all mu coworkers bringing their emptied jugs in!!! Hahaha yay!
     
  19. USEBOTHHANDS

    USEBOTHHANDS New Member

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    wear your rain gear. :D
     
  20. armsmaster270

    armsmaster270 New Member

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    +P ammo information per Wikipedia.
    Commercially available +P cartridges

    Cartridges that are commonly boosted with +P pressures are the 9 mm Luger, .45 ACP, and .38 Special, which are all cartridges that date from the dawn of the 20th century. There has been significant improvement in metallurgy and quality since the first guns in those calibers have been made, with the result that higher pressures are now safe in modern firearms. Many models will specify to the degree they can use +P ammunition; for example, many aluminum alloy framed .38 Special revolvers should not regularly be used with +P ammunition, for while the cylinder is capable of withstanding the pressures, the added force will increase wear and reduce the service life of the gun.
    SAAMI specifications for common +P cartridges are as follows:
    Cartridge Standard pressure +P pressure Notes
    9 mm Luger 35,000................ 38,500 10% increase
    .38 Special 17,000................ 18,500 9% increase
    .45 ACP 21,000................ 23,000 9.5% increase
    .38 Auto 26,500................ 36,500 38% increase to make .38 Super
    .45 Colt 14,000................ 27,500 96.4% increase, For use in certain modern revolvers and lever rifles
    The +P+ designation is not currently used by the SAAMI, but is used by some manufacturers to designate loads that exceed the +P SAAMI specification. One source lists the 9 × 19 mm +P+ loading as having a pressure of 42,000 psi, an 18% increase over the standard pressure of 35,000 psi, and the .38 Special +P+ as 22,000, a 29% increase over the standard pressure.[5]
    Small ammunition makers and reloading guides will often include special loads for specific purposes, such as the above listed .45 Colt load from Buffalo Bore Ammunition. These loads are generally designed to provide maximum performance from older cartridges, when used in newer, stronger firearms. The 14,000 psi limit for .45 Colt, for example, reflects the black powder performance of the round, and is safe even in firearms built in 1873, when the cartridge was introduced. Using modern, solid head brass in a Ruger Blackhawk revolver, a similar design originally chambered in the high pressure .44 Magnum, the pressure can be pushed far higher with no ill effects. However, since these loads, with nearly double the pressure, could destroy a firearm intended for black powder level loads, they are less commonly encountered.

    38Spl +P+ Box

    [​IMG]
     
    Last edited: Oct 4, 2012
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