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

Discussion in 'General Discussion' started by Fiftydriver, Jun 26, 2008.

  1. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Simple question:

    For those that have tested the 300 gr SMK in any 338 caliber chambering, how many have proven that this bullet will remain consistantly accurate through the transonic section of bullet flight?

    In addition to that, how many have seen this consistancy remain in the 1/2 moa range well beyond the drop below super sonic velocity?

    Your actual experience and experience wanted.

    Thanks for your time and information, very curious to hear the results you have gotten. Once I get some information, I will disclose the reason why I ask this question.
     
  2. michael A.

    michael A. Well-Known Member

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    BTT

    looks like you are just going to have to tell us what is up your sleeve gun)
     

  3. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    ok, fair enough. There was an article in the last issue of Varmint Hunter Magazine by Gordy Gritters. Its about his 2 mile shooting.

    In the article he talks about his new 33 cal magnum, basically the same as a 338 Lapua Improved, nearly identical to my 338 AX. He lists he is getting the 300 gr SMK to 3000 fps which in a proper barrel length would seem to be a pretty mild load so no problem there from me.

    My problem comes when he started talking about the groups he and another shooting companion were getting at 3600 yards. His claim is that he put 16 shots into an 18" group at that range, thats 1/2 moa accuracy.

    That alone would be a serious accomplishment but what I have a problem with is that in all the testing I have done with the 300 gr SMK, in rounds such as the 338 RUM, 338 Edge, 338 Lapua, 338-378 Wby, 338 Allen Xpress, 338 Kahn and my big 338 Allen Magnum, in every case, every single case I have tested these rounds to see where the consistancy of the bullet drops off.

    In every case, it happens within 100 yards of where Exbal predicts these bullets will drop out of super sonic velocity at my elevation. IN EVERY CASE. I have tested this with 1-7, 1-9, 1-10, 1-11.25 and 1-12 twist barrels and it seems to make no difference what the RPM level of the bullet is, when it drops below super sonic velocity, the consistancy of the 300 gr SMK is simply gone.

    I am not saying the accuracy degrades, it flat out is gone. With my 338 AX or the 338 Kahn loaded to the exact same or slightly higher velocity with the same bullet in the same twist rate barrel, they will drop out of super sonic velocity aroung 2450 yards at my elevation. We have tested this extensively. At 2300 yards, these chamberings in good conditions will easily shoot under 1 moa, generally under 3/4 moa and at times less then 1/2 moa.

    At 2600 yards, there simply is no accuracy and it is even difficult to see bullet impacts. If you do see them, it is not uncommon to see them land in 20-30 FEET groups.

    With my 338 AM, the 300 gr SMK can be loaded to a level where it stays super sonic out to around 2800 yards. Again, I have tested the consistancy of this chambering with this bullet. AT 2700 yards, consistancy is great, hits and impacts are accurate and predictable to place from drop charts.

    Set a target out at 2900 yards, same results as before, if you can see the bullet impacts they are wildly spread with no real consistancy at all.

    I can jump up to the +.9 BC wildcat prototype 265 gr AT RBBT and load it to 3540 fps and accuracy will remain out to just over 3000 yards, the farthest I have tested so far. Exbal predicts that this bullet will drop below super sonic velocity at around 3150-3200 yards and I am confident this bullet would have the same fate as the SMK as it drops out of super sonic velocity.

    So, I simply had to call Gordy out on this one, e-mailed him and asked what magic he was using to get these bullets to hold 1/2 moa for 1000 yards AFTER they have dropped below super sonic velocity?

    I have not heard back from him yet. I suspect the response will come in one of two forms from my dealings with him in the past and what I have heard from others about the man.

    1. He will not respond which in my mind will tell me there is a bit of stretching the trueth going on here.

    2. He will personally attack me, my experience levels and the rifles I build.

    I fully expect it to be the latter of the two.

    He has posted several articles over the last few issues of VH magazine which have really raised some questions from not only me but many other truely experienced long range shooters. The best gunsmiths in the world can not spit in the face of ballistic laws or physics but it seems Gordy believes he can.

    Basically from his writings, as long as you have enough moa adjustment to put the x on the spot, you can accurately put bullets on that spot with great accuracy. I know it to be a fact that is not true and many on this board do as well.

    I figured it was just time to call him out on his comments and hopefully get a respectful reply from him debating the topic as my e-mail to him was very respectful.

    Anyway, that is my reasoning for the question. If any of you have seen this same magic with the 300 gr SMK remaining fully stabilized after dropping out of super sonic velocity I would be very interested to hear about it. I understand there are always anomolies where strange things occur, but keeping this bullet accurate to 1/2 moa for not 3, not 5, not 10 but for 16 shots at 3600 yards, that is something I would have to see first hand to believe.

    Not on video either.

    he also made claims that they hit 3-4 prairie dogs at this type of range but none were recovered for proof. Convienent. If you can out 16 shots into 1/2 moa at that range and you were hunting dogs for the entire weekend, not getting a picture of a killed P. Dog would be nothing but a failure in my opinion. But again, in my opinion, we are dealing in a relm of ferry's and pixie dust!!!
     
  4. Eaglet

    Eaglet Well-Known Member

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    I'm all ears on this one!
     
  5. J E Custom

    J E Custom Well-Known Member

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    Kirby

    Now I have to buy the magazine and read this one!!!!

    I'm from Texas and we have elevated bull s#!ting to an art form,
    but this one is a little tall for me. It sounds like claims of gas mileage
    (allways higher than anyone else can possibly get by 3 or 4 miles per gallon).

    Or maybe he just has a bad range finder.

    If he does reply please share it with us.

    Waiting
    J E CUSTOM
     
  6. davewilson

    davewilson Well-Known Member

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    his rangefinder is probably reading in feet, not yards. i'll bet in the winter, when a cold snap rolls into his neck of the woods, it's 5 degrees colder at his house than anyone else. and yes, in the summer, it's always 5 degrees warmer!
     
  7. Tyler Kemp

    Tyler Kemp SPONSOR

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    Does anyone have a small 338 caliber cartridge? Something like a 338-223? You could load the 300 SMK to maybe 1300 fps and see how it shoots at 100 and 200 yards. Should simulate the transonic buffering or whatever it's called with the bigger 338's at extended range.
     
  8. James Jones

    James Jones Well-Known Member

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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
     
  9. bwaites

    bwaites Well-Known Member

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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
     
  10. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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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.
     
  11. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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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.
     
  12. michael A.

    michael A. Well-Known Member

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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?
     
  13. Desert Fox

    Desert Fox Well-Known Member

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  14. Tyler Kemp

    Tyler Kemp SPONSOR

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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.