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300 gr SMKs consistancy dropping out of Supersonic velocity...

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  #8  
Unread 06-29-2008, 05:35 PM
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I'm with Kirby , 2 miles is a long poke for a shoulder fired weapon of any caliber. Not saying that it can't be one , I'm sure that their are things that are certainly considered "other worldly" that happen everyday.

I'm not sure if its the bullets problem that is causeing the crazy accuracy drop off. I have heard for guys thats oppinion and word meen alot to me say that their are shoots where the 220 and 240 Sierra Match King fired out of a 308 and 300 winchester shoot to 2000yds , I'd call total BS on that one but these boys swear it happens.
I have also personaly seen some big black powder rounds like the 45-120 and 50-120 shoot out to 1600 yds and those bullets are starting out WAY slower and have half the BC that the SMK does. I think that its realy just an mystery with some guns. I also have a 9mm upper for my AR here that will group in the 6" range at 200yds (with a higher power scope) both with supersonic and sub sonic rounds , I figured that it would pattern in yds rather than group at all.

BUT , I do find it strange that he is shooting the same bullets out of guns built very well I assume and he is having no troubles.
Maybe he is shooting them out of a 30 cal barrel in turn streaching the bullet way out making it more spear like than before , maybe with a BC of 1.9 !!:p
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  •   #9  
    Unread 06-30-2008, 12:57 AM
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    I'm no expert on this, but having talked with LOTS of guys who shoot the .308 SMK's, they generally admit to a big drop off in accuracy in that transonic range as well.

    I cannot imagine that it doesn't happen, else everyone with a decent rifle would be able to shoot great loads at 2K from their .308's!!

    Bill
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      #10  
    Unread 06-30-2008, 01:06 AM
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    Tyler,

    The idea is a decent one but you would need to use a very fast twist rate to duplicate what would ACTUALLY happen with the larger magnums at long range.

    The reason, if you shoot a 300 gr SMK in a 1-10 twist at 3000 fps you will generate a certain RPM level.

    If you drop the muzzle velocity to 1300 fps in the same 1-10 twist, the bullets RPMs will be extremely low compared to the larger magnums.

    Even at long range, while the RPM rates have dropped some compared to the muzzle RPM levels, the decrease is very marginal.

    If you could get a fast twist barrel to match the RPM levels of the larger magnums, the test could have some usefullness.

    It would be a cleaver idea to test things out through.
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      #11  
    Unread 06-30-2008, 01:11 AM
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    I have witnessed blackpowder rifles do amazing things at long range but this is for a very specific reason, the bullets they use perform very well at long range and generally, they are relatively short and stubby with flat base designs. Also, very rarely are they fired at velocities much over super sonic velocity.

    Short fat bullets have been proven to hold accuracy and consistancy much better through the trans sonic phase much better then long, sharp ogive, boattail match bullets.

    A VLD type bullet that is fired just under super sonic velocity is extremely efficent and accurate over very long ranges but I have yet to see a test where these bullets accuracy drop out of super sonic velocity and remain accurate for 1000 yards past this point in velocity.
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    Kirby Allen(50)

    Allen Precision Shooting
    Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

    Farther, Faster and Flatter then ever before.

    Web Page: www.apsrifles.com

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      #12  
    Unread 06-30-2008, 01:35 AM
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    ok kirby

    if a .338 bullet wont hold accuracy and consistancy through the trans sonic phase will a .375 bullet or a .410?
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      #13  
    Unread 06-30-2008, 01:40 AM
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    Not the 300 SMK but the 250 Scenar at 2000 meter. The Remaining velocity is around 705 fps at 2K.

    Amazing trajectory calculations - Sniper's Hide Forums
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      #14  
    Unread 06-30-2008, 08:47 AM
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    Ah, I wasn't thinking it through enough. Don't know of any other way to test it than the real thing.
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