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Hornady Superformance? GMX?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/25/2010 at 14:49
TexasPhotog View Drop Down
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Anyone shot the Hornady GMX bullet?  How'd it do? 

Also, can anyone explain to me how Hornady can do this: "Superformance ammunition is 100 to 200 fps FASTER than any conventional ammunition on the market today, and achieves this performance in EVERY gun, WITHOUT increases in felt recoil, muzzle blast, temperature sensitivity, fouling or loss of accuracy."

Their stats of 3200 fps for a 130 gr .270 round are impressive, if true:

http://www.hornady.com/store/270-Win-130-gr-SST-Superformance/
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/26/2010 at 07:44
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AA's MagPro powder has been listed as pushing a 130g .270 Win. at 3239 fps for several years now.  The change in velocity for the .270 is less than 5%.  Most people won't be able to tell a 5% increase in felt recoil.  Not sure about some of the other claims.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/26/2010 at 08:13
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Hornady's explanation is that they're using new powder blends that provide a more efficient burn rate and pressure curve.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/26/2010 at 09:16
TexasPhotog View Drop Down
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3200 fps (if true) is pretty zippy though for factory ammo for factory ammo.  Most other factory ammo's are listed at 2950/3000 and I'd bet most of them don't really make that.

Anyone used the GMX bullet on game?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/26/2010 at 18:14
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Not the gmx bullet, but I have a big fan of Hornady bullets.  As long as you use bullets designed for the game you intend to hunt, I doubt you'll have any problems.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/28/2010 at 18:44
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I’ll try to answer these questions. To get the most velocity you have to match the burn rate of the powder to the weight of the bullet and the length of the barrel.  So fast powders spike to maximum pressure but dissipates while the bullet is still in the barrel.  Slower powders burns at a lower pressure longer and can push the bullet the entire length of the barrel and the velocities increase in comparison.  Use too slow of powder and it will not be entirely used and the excess powder will continue to burn after the bullet is out of the barrel, which results in a big flash that we have all seen from time to time. It looks cool but doesn’t add anything to the velocity, but it does add to the recoil.  That muzzle flash also pushes the air farther away from the barrel creating a momentary void in the air and as the air returns back to the ambient atmospheric pressure it adds to the duration of the recoil.  A good visual example is a nuclear bomb blast.  The detonation pushes the air out causing the void.  As the air returns it picks up all the dust and debris as it heads back to the point of origin.  All that pressure has to go somewhere and the path of least resistant is up because the higher the altitude the less atmospheric pressure.  So it produces a big ass column of dust and debris, then spread out at the top because very little atmospheric pressure and forms a symbol of power; the mushroom. Smile  OK a little too much information.  I suspect that Hornady used a baseline of 14 to 16 inches of pressurized bullet travel (duration of powder consumption), then the residual pressure would be pretty close to ambient pressure in a 22 to 24 inch barrel.  More speed and not a noticeable difference in recoil are achieved.  Temperature sensitivity is an issue in itself.   Any deviation in the formulation or processing of energetic material can cause temperature sensitivity even with the most stable ingredients.  Some are more susceptible than others for instance ball powders have been blamed over the years to be temperature sensitive and the reason is there is more burn surface per weight.  In already short burn duration the pressure jumps if more heat is added.  Any slight changes can affect ball powders more than extruded powders.  The trade off is the ball powders have more predictability and burn consistency than the extruded powders.  That is why you see more consistent velocities from one shot to another with ball powders compared to extruded.  Plus you can load more rounds per pound and it throws or measure more consistently, which is a cost savings.  There wouldn’t be any more fouling if the propellant is completely consumed than any other powders. To hit a proper burn rate they may have used a blend of different lengths of extruded powder where the one is cut long the next is cut short for instance.  Mixture would be pretty consistent because the same materials same extruding machine same process.  All in an effort to get the correct burn surface/burn rate for a specific cartridge.  At least that is the way I would do it.  If you hit a consistent burn rate in concert with the consistency of other components it would be inherently more accurate.  Yes they are right in their advertisements “it is rocket science”.  I was in it for 35 years before I was Obamaized. 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/28/2010 at 23:39
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Wow!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/29/2010 at 08:08
Dale Clifford View Drop Down
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powders don't have a burn rate in the sense of physics ie, units of wt/time -it a burning index. as long as pressure differential exists between the inside of the barrel and the outside pressure the hot gases will push the bullet, the pressure acceleration curve is flat after the first 1/3 of the barrel using either fast or slow powders. if the bullet is pushed to a higher velocity its because that powder simply has more energy in it than (chemical) than another. If you were to choose a "fast" powder that had the same molecular wt. of nitrates as a "slow" powder the bullet velocity would be the same, (although the gun might not be) some powders certainly are more efficient than others than this regard. excessive muzzle flash doesn't add to recoil -- the recoil difference is simply the wt. difference in the exit velocity of the gas mass, not the pressure differential, if a higher recoil is obtained from a flashy powder, the powder wt. was simply higher. Exit pressure can be as high as at least 4x atmos. this is what makes muzzle brakes work (breaks). extruded powder such as Varget and benchmark are pretty much more consistent than ball powders and less temperature sensitive.
An optimized powder (and thus pressure) would be were the derivative of the work curve crosses the velocity deceleration curve using pressure as a baseline in the shortest barrel possible.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/29/2010 at 08:13
Dale Clifford View Drop Down
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http://shootingsoftware.com/pressure.htm
if you want to explore this area which is one of the most interesting in the area of handloading.
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