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  1. #11
    Join Date
    Dec 2007
    Location
    Illinois (the good part)
    Posts
    16
    Quote Originally Posted by CB3 View Post
    Comparing loads between manufacturers based on velocity is more meaningful when the test barrel length is specified. Be careful of apples to oranges comparisons. Shorter barrels will deliver lower velocities and may affect terminal performance depending on bullet design.

    The standard pistol test barrel length used to be 5” and many ammunition manufacturers quote velocity based on 5”.

    However, with the proliferation of concealed carry shrinking common barrel lengths to around 4” (-20%), manufacturers have had to tweak bullets for bullet performance at lower velocities.

    A full size gun, like a Glock 34 or a 1911 has 5+” barrel.

    The compacts like the G19 have 4.5” barrels.

    However, the subcompacts like the G43 and the Shield have barrels just over 3”. A 3.3” barrel is about 40% shorter than a 5.2” barrel. The bullet does not have the same acceleration time in a shorter barrel.

    When you choose ammunition for a sub-compact, terminal performance based on 5” ammunition tests may be meaningless.

    Of note, the ATG test video Gabe linked to above used a 3.1” barreled S&W Shield and got stellar results. Unfortunately, they did not chrono that load. However, the Black Hills load is able to get the bullet up to good performance velocity even from a short barrel. Everything BH loads is top shelf stuff.

    I carry the Barnes ammo because I can get it easily. It performs as well as the BH. Certain other loaders also have excellent load development and quality control, which is necessary for the TAC-XP as it takes a very different set of parameters to load well.
    The test firearm in the LG test is listed as a S&W M&P 9C for all loads which I believe has a 3.5" barrel.

  2. #12
    Join Date
    Oct 2005
    Location
    Utah
    Posts
    1,010

    Default Another terminal performance issue

    As Gabe pointed out, having the most devastating terminal bullet performance is part of the total package for effective shooting.

    A jacketed lead bullet that mushrooms becomes basically a larger cylinder, assuming it mushrooms evenly and retains its weight, which is not always the case.

    Bullets rotate as they fly. Enlarging the face of a bullet as it rotates, even using that rotation to help it mushroom, adds to its effectiveness over a non-expanding bullet, but it is still basically just a cylinder pushing a shockwave ahead of it.

    However, the larger that bullet expansion without slowing the bullet down and decreasing penetration, the better, AND if that larger diameter at high rotational speed is cutting through tissue as well as plowing through it, you will have more terminal effect. In other words, the propeller-like petals of the expanded copper Barnes TAC-XP Bullets can inflict more damage than a spinning mushroom.

    Here is the formula to calculate the spin rate as the bullet leaves the barrel: (MV x 720)/twist rate = RPM

    Muzzle Velocity in feet per second x 720 divided by the denominator of the twist rate in inches = Revolutions per Minute (RPM)

    So, a bullet exiting a barrel at 1,000 FPS, x 720 = 720,000 divided by 10 (for 1 twist in 10” barrel, common for many 9mm) = 72,000 RPM. Dividing that Minute by 60 gives you 1,200 rotations per second. (Or just multiply by 60 instead of 720 in the base formula for revolutions in seconds instead of minutes.)

    Obviously, as the bullet encounters resistance, the spin rate decreases very rapidly. In truth, a mushroom shaped expanded bullet as it slows just pushes through its wound channel less effectively. The Barnes bullet, however, continues to slice and dice while spinning, even as it is slowing. This bullet design gives maximum terminal effect through the whole wound channel. High speed gel block photography actually shows the Barnes “propeller” slicing with longer cuts as it slows. Really quite amazing. As well, the spinning/cutting action allows for deeper, straighter “stabilized” penetration with what is actually a light bullet that penetrates like heavier ones.

    Lighter bullets usually produce less recoil = faster shot-shot recovery.

    These are nuances that in sum make for a better bullet, IMO.
    "... men and women of your armed forces America having signed a blank check to the protection of the American people and to the defense of our constitution, a check payable with their very lives, your military stands ready and confident to defend this country, this experiment in democracy.” Secretary of Defense James Mattis, 9/11/17

  3. #13
    Join Date
    May 2016
    Posts
    602
    CB,
    Thanks again for sharing your engineering
    insider info.

    John
    "Play stupid games, win stupid prizes" Alan Temby

  4. #14
    Join Date
    Jan 2012
    Location
    NW Washington
    Posts
    2,922
    Quote Originally Posted by CB3 View Post

    Lighter bullets usually produce less recoil = faster shot-shot recovery.
    Yes. Carrying that line of thought a little farther, I personally like hotter loads in the full size guns, G17/34 etc because they're still relatively easy to shoot fast, but will give up some bullet weight and velocity in the small guns (G43, Shield, Kahr, etc) to regain some of that ability to shoot fast with precision.

    For example, a 124gr +P+ load in a G34 is about as easy for me to shoot as a standard 115gr load in a pocket gun. Either one can still use the same ammo in a pinch of course, but I don't mind using a different load to get the most out of a specific gun.

  5. #15
    Join Date
    Nov 2016
    Location
    Under the Black Flag
    Posts
    175
    Speer Gold dots.

    No fancy bells and whistles, but a good bonded HP round.

    I have been to many autopsies and have seen projectiles do many odd things, but 99% of the Gold Dots I have seen open, don't over penetrate the target with a good COM hit and open while retaining their mass. This is with 9mm, .45 acp and 5.56.

    Other brands do odd things. I have NOT seen any of the solid copper projectiles, so I have no horse in that race, but I have heard lots of good things about them from hunting buddies.

    When I intend to shoot four legged or two legged critters I carry a good bonded HP/ST round. They just work.


    My two pennies onto the pile, take it for what it is worth to you....

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