Have any of you seen "magic" like this?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by kraky2, Jan 1, 2009.

  1. kraky2

    kraky2 Well-Known Member

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    In a recent read of one of the gun magazines a writer was talking about his 25 caliber rifle and how it magically shoots flatter than it should. I think it was a 25-06 with a 100 grain tsx.
    He said he had it zero'd 2" high at 100 yds and at 300 it was still up 1" high and at 400 was down like 6". Someone ran a bc calculation and said the bullet seemed to be achieving a .800.

    I'm not calling this a fib but was wondering if some of you long range guys can explain what's happening here or if you have a couple of matching stories with your rifles. Can some sort of scope cant or wierd barrel fitting phenomenon be at work? BTW the load he describes is really accurate so there is good bullet stabilization there.
     
  2. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    Trajectories like this are possible if the scope is mounted high above the barrel. Running some rough calculations suggests that the trajectory you described would be possible with a scope that's mounted about 3.5" above the bore. For less dense air (less dense than standard sea level conditions) the height wouldn't have to be so much, maybe 2.0" for 80 degrees at 5000 ft elevation.
    There is not as much 'magic' in shooting as commonly believed, although occasionally we come up against some real stumpers!
    -Bryan
     

  3. Coyboy

    Coyboy Well-Known Member

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    I agree with Bryan, and then that fellow that just shot the trajectories in the field goes home to his puter and adjust the bc to match the drops. The whole time he leaves scope height at the defalt setting of 1.5".
     
  4. Broz

    Broz Well-Known Member

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    This is funny. I JUST got home from the range. One of the guns we tested was my Accumark 30-378. Since I have two I am setting this 30-378 up to be a point blank carry rifle. The new load is with 168 gr TSX's at between 3550 and 3590. Haven't averaged them yet. The scope is a XVIII 4.5 x 14 x 50 mounted 1.9" above the bore. Sighted in at 2 1/2" high at 100, it was dead on at 300, and only 2 1/2" low at 400. But it drops bigtime from there,, it was 19" low at 500. So I have what I wanted, a carry rifle that you shoot dead on to 400.

    Jeff
     
  5. Coyboy

    Coyboy Well-Known Member

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    Jeff, somwhere in that trajectory path your bullet is going to be at least 6-7 inches above your line of sight. I would shoot at 175,200,and225 just to see exactly what it is.
     
  6. Broz

    Broz Well-Known Member

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    Coyboy,
    I just ran it through my PC Ballistic program. But I always check in the field to be sure. It is pretty much spot on to 500 with a drop at 500 being 19.3". My actual group was under 3" and center of group was 19" low. You are right though, it does show a rise of 3.7" @ 175 yards. I went right from 100 to 300 so this is probably right. I will confirm next trip. Still if it will shoot with less than a 4" poi 400 I will be happy.

    Thanks for pointing it out.


    Jeff
     
  7. Michael Eichele

    Michael Eichele Well-Known Member

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    I have experianced this myself. I had one load I tested and after I settled on it I zeroed it at 300 yards and took it to 600 yards for some longer range testing. I used my 3rd bar on my NPR2 reticle for 6 MOA of drop. I just wanted to get on my target backer so I could determine how much to bring it up knowing my group would be much lower than the bulls eye. After driving down to the target I saw the group in the very center of the target. I had just bought a new NF scope and was dertermined that the wrong size reticle was installed in my scope. After checking the scope for demensional accuracy I became a believer. My BC was off the chart. Something like over 1.000 for a 178 AMAX. Sometimes the sum of the parts balance out perfect and we see the impossible. It doesnt happen often but happens sometimes. Most of the time it is some other mathematical error. Sometime youre lucky. When the stars align, good things happen.

    Jerry Teo has also seen similar results in a couple of his rifles.
     
  8. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    Michael,
    Are you saying that you believe the 178 Amax bullets can actually fly with a BC of over 1.000, or that some combination of variables presents the illusion that it's happening?
    -Bryan
     
  9. Michael Eichele

    Michael Eichele Well-Known Member

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    I dont know why it happened. I just know it happened. Has it happened for me in every rifle? No. In fact it only did it for me in one rifle and it was a given load to boot. Call me crazy. The bullets were only dropping 6 MOA at 600 yards and should have been dropping 7.85 MOA. In case youre wondering, yes, I know how to calculate proper ballistics. This is the only time I have ever experianced this. The next closest thing was the 190 SMK in my rig yielding a .563 BC and the 155 AMAX which was giving me a .474 BC (0.014) over published, which is only slightly above published. Most other bullets I have used offer less than published.

    Now I am not going to sit here and tell you that it couldnt be other variables to offer an illusion of a ultra high BC but I certainly could never figure out what those variables could be. It was what is was.

    All atmosperic data was collected and calculated minus humidity, zero was spot on at 300 yards. No my sight height was not misscalculated.

    In short yes I believe a given bullet in perfect harmony with all of the factors that go into internal and exterior ballistics and their relationship with eachother can in some circumstances give way to BC's that are off the chart.

    I guess you have never had such an experiance?

    There is a link below from some time ago about when I originaly had this phenomenon. Jerry Teo shared similar results with similar bullets.

    http://www.longrangehunting.com/forums/f19/i-am-soooooo-confused-heeeeeeeelp-12714/
     
    Last edited: Jan 1, 2009
  10. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    Using drop to calculate BC is a risky thing. The uncertainties in group center, consistency of sight adjustments, vertical wind currents, and other less well known tangibles can cause HUGE swings in a BC that's calculated from observed drop. It can be done, but it has to be a carefully controlled and sterile test environment which most of the time it isn't.
    I'm not 'callin you out', but I personally don't believe that a projectile can magically achieve any kind of supernatural drag reduction that would cause it to fly with a much higher BC than other similarly shaped bullets. I DO believe that conditions can exist that can REDUCE the effective BC of a bullet fired from a particular barrel like marginal gyroscopic stability and excessive initial yaw rate induced by barrel whip. However, when a bullet is fired with adequate stability, and it flies with no yaw thru the atmosphere, that bullet still has to pay the energy bill it takes to make all that noise and heat. It pays with work (forceXdistance), and that energy is subtracted from the bullets kinetic energy. There's no way around it, even if we think we're seeing it.
    I have seen things that were inconsistent and gave me pause on occasion, but something usually surfaces that explains it like a misreading chronograph, or some other malfunctioning piece of instrumentation. I have no problem dismissing the measurements that defy the law of conservation of energy whether I discover the exact cause of the error or not.
    -Bryan
     
  11. Michael Eichele

    Michael Eichele Well-Known Member

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    I have no problem with that whatsoever. If you have never seen it or experianced it I wouldnt expect you to. I know you have a healthy amount of experiance in exterior ballistics. Can you tell me you have never seen anything bizzare? Not neccesarily what we are discussing here but bizzare none the less?

    My concern was when (on a windless day) I can lay in the same spot and shoot my 308 winnie (a solid .25 MOA rifle) with the same bullet at a side by side target as my 300 RUM (another solid .25 MOA rifle) target and get a G5 .318 BC with one and a G7 .495 with the other using the exact same bullet. I know what youre saying about using drops to calculate BC's (this is why I currently use the 2 chronograph method between 15 feet and 300 yards) but when I am not touching the knob and using a proven 2 MOA reticle x 3 bars and the groups are concistently falling on center, to me that is a fair degree of conclusion. Its the day to day concistency that gave me more conclusion. Like I said. It was what it was. Whether I believe in supernatural ballistics or not. For the record I do not believe in superantural ballistics, just when the sum of all parts work in perfect harmony non typical things can happen.
     
    Last edited: Jan 2, 2009
  12. Michael Eichele

    Michael Eichele Well-Known Member

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    Please understand my posts here are in no way intended to argue with you. I would love to know if I was doing some function wrong and what that was. I was never been able to figure that out then or now. Was it a mathematical error of sorts or just some bizzare results? I may never know as I no longer use that barrel.
     
  13. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    Micheal,
    I don't take your posts as argumentative at all. I know you're a knowledgeable shooter yourself and take your (and others) observations seriously. I'm here to learn just like everyone else.
    Can you tell me about the particular barrel; was is a thick heavy bull barrel or a thin sporter barrel?

    I'll tell you the one I'd really like to get to the bottom of is the phenomena where rifles group smaller in MOA at longer range than short. I've never directly observed this myself, however I did have a 7mm Rem Mag Sendero that 'seemed' to group ~0.75" at 100 yards and ~1.00" at 200, but of course the only way to know for sure if the groups actually 'converges' is to shoot thru two targets at once. There's just too much anecdotal evidence on this one to ignore it and I can't figure it out. My current hypothesis is parallax. Scopes that are properly adjusted for parallax at 200 yards will have some aiming error at 100 yards if they're not properly adjusted. I can't find anything physical to explain how a group of shots would converge in from all sides as range increases.

    There are some unexplained things that happen, but rather than conclude that something unnatural is actually happening, I choose to accept that I simply don't know enough yet to explain everything and keep an open mind in search of the answers.

    Take care,
    -Bryan
     
  14. Michael Eichele

    Michael Eichele Well-Known Member

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    Bryan,

    The barrel was a 27.25 Lilja, 12x heavy varmint contour. .333 tight neck 300 RUM.

    I know what youre saying about tighter MOA's at longer ranges. I had one load that was not only tighter MOA but smaller in inches at longer ranges. It was shooting concistent 1 MOA groups out to 600 yards and sub 0.5 MOA at 1K. In other words I was getting 6" at 600 yards and under 5" to 5" at 1K????????????????????????????????????????????????

    I had an ex military sniper instructor explain it to me once. I am running late and have to jam, but will entertain his thoughts when I get home tonite. I am not saying he is right, but he made alot of sense.