The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Rifles Medium Bore Rifles Poll - Trajectory goes Up, Down, or possibly both for a Higher Velocity?Go | New | Find | Notify | Tools | Reply | |
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| One of Us |
So! My next question is............. Why do two different powders, producing the same velocity, give different points of impact, as well as different group sizes? | |||
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pressure curves, recoil characteristics of the barrel, harmonics, and when i have a rifle so finiky that it shoots big differences, it get sold, along with the secret sauce opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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What jeffeosso said +1! I have been trying to tell people that for years. Most can't grasp it. God Bless, Louis | |||
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Higher all counts. Any object traveling at a higher speed resist gravity longer. | |||
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and here's some simple PROOF situation 1 - 70gr load, barnes 450 TSX and 450 solids .. something like 5" apart at 50 -- tsx hitting higher than solids... situation 2 72 gr with tsx, and 69gr with solids bullets now impacting some point of aim at 50 slowed the lower solids, and they came UP .. speed up the higher softs, and they came DOWN... and this happens each and EVERY time http://forums.accuratereloadin...871059621#7871059621 lift, drag, and sunspots have nothing to do with it, within a 10-15% spread of velocities.. angle of release from the muzzle, arch of bullet flight, and IF IT IS THE SECOND time the bullet crosses the line of sight. if its within 25 yards, it will be under the sight plane .... opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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Not only does velocity matter to POI, but, you're right HC, velocity changes the harmonics of the barrel. Many times while shooting Audette's tests some higher velocity rounds impact lower on the target than some of the lower velocity rounds. This is due to where the barrel harmonics have made the muzzle point at the time of the bullet exit. It's explained very well here: http://www.varmintal.com/alite.htm#Ladder So in answer to your poll, I think that generally higher velocity rounds impact higher as compared with those of lower velocity.....but not all the time. Sorry jeffeosso, I just read your link and your last post on the thread you referenced. In my experience going slow does not raise POI and speeding up does not lower POI Here is a 500 yard Audette's with a .300 WM and the 168 gr A-Max  You'll see two accuracy nodes. The higher velocity node printed higher. I began to shoot an Audette's yesterday with my .264 WM and the 130 gr Accubond. The higher velocity node of accuracy printed about the same location as some of the lower velocity shots (none of which indicated a node of accuracy). My gun broke before I could fire the last 5 shells which would be of higher velocity/powder charge. I'll have to report back with findings but I'd bet those last 5 shots POI would be higher. | |||
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| <Andrew cempa> |
R; I agree-using the Audette method harmonic nodes show some up and down cycling, but the node always climbs, the trend is never overall downwards (in my expereince). As I am sure you know, the charge weight that is between both the up and down node window is normally the most accurate. Example- 5 round cluster in a tight knot with a charge spread of +/-.2 grains (.4 grain total, let's say) will likely always be a good performing load at every distance and takes advantage of the variation of the powder measure tolerance.... Best | ||
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I chose "May do either" as a changing in velocity would have a change in barrel harmonics. The bullet may exit during a peak (node) and thus the bullet may go higher, lower, left, right, or remain the same at the moment the bullet leaves the barrel. Sonar59 | |||
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You're right. There's so much movement going on it's amazing that anyone can get a rifle to shoot accurately. Have you ever seen a super-slow motion video of a rifle or shotgun during firing? Unreal!! Check out some barrel harmonic movies on Varmint Al's site: http://www.varmintal.com/amode.htm | |||
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NRA Life Member since 1976 philny1@zoominternet.net 877 485-6270 Visa/MC accepted , plus 3% We have to save the Earth, only planet with beer!! "Peace is that brief glorious moment in history when everybody stands around reloading". Thomas Jefferson | |||
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I'm not sure there are real answers to these questions...theoretically there should be but many things happen contrary to theory when firearms are involved..... My own experience with a much slower round (the M-92 in .25-20) is as follows: I converted three of them from shooting the standard 86 grain flat nose to the 60 grain HP or flat nose..... The 86 grain load travels about 1600 FPS and the 60 grain load travels about 2200 FPS....quite a dofference for sure!! In all circumstances I had to install a new front sight considerably higher than the original to re-zero the rifle! My guess is that when one is dealing with velocities over 2,600 FPS he is not going to be so lucky as to be able to predict the changes. /////////////////////////////////////////////////////////////////////////// "Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery." Winston Churchill | |||
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 All else constant, an increase in mv will cause a higher impact on target. If not the laws of physics are wrong. Handloaders experience changes in point of impact that don't make sense like a faster load hitting lower on target. This is related to barrel harmonics, sight height and other variables that I'm not sure are well understood by most of us (not me). Whenever I think I've discovered something that deifies scientific understanding it turns out that I'm wrong, not science.  ---------------------------------------------------------------------------------------------------- If the 270 won't do it the .338 will, if the 338 won't I can't afford the hunt! | |||
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| Moderator |
Wayfayer .. Happy to meet you at a range, with rifle, loads, and chrony! opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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| new member |
[QUOTE]Originally posted by egb243: I completely understand trajectory and agree that a bullet flies in an arch to hit a 100 yard target. I also agree that a bullet dose in fact pass thru the line of sight, rises above it and then drops into the target. At least at most ranges that we shoot at. But the fact remains that bullets do develop a slight lift component during flight and they do lift slightly –very slightly but none the less they do have some lift to their flight. -- They do not fly with their point directly on axis to the line of flight but do fly with their nose pointed slightly up to the line of flight and do develop a slight lift component. Therefore a bullet in flight will not hit the ground at the same time as a dropped bullet or bowling ball or any other solid object. I completely do agree that a dropped bowling ball and a dropped bullet would result in both hitting the ground at the same time provided the bullet wasn’t shot from a rifle and flying thru the air, even if the bowling ball has the arch of the bullets flight factored into it's fall, it would hit the ground and the shot bullet would still be flying after the bowling ball hits the ground due to it's slight lift component. This is interesting and I haven't heard it discussed for a long time. The "lift" associated with projectiles that are not airfoils is "ground effect" (the bullet pushes air out of the way raising the pressure equally on all sides unless something gets in the way, like the ground, which creates a "cushion"). This same effect causes the bullet to vear left or right when going past a tree, down if going under somthing, and presumably would allow it to fly its perfect segment of a spiral if flying through a culvert bent to match the trajectory where the bullet stays in the center. 'Never heare the one about bullets flying nose high though. Sorry to babble so much and I don't mean to changs the subject of the thread. | |||
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Chrony won't tell you what effect barrelharmonics ect are having on the POI.  Know a good range BTW?? I'm sick of some of the Yahoos that shoot at Carters. ---------------------------------------------------------------------------------------------------- If the 270 won't do it the .338 will, if the 338 won't I can't afford the hunt! | |||
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Also just messing around with the ballistic calculator... If your target is closer than your rifles zero, a decrease in velocity will cause the POI on that target to go up. ---------------------------------------------------------------------------------------------------- If the 270 won't do it the .338 will, if the 338 won't I can't afford the hunt! | |||
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This is your speculation or do you have a source for this info? ---------------------------------------------------------------------------------------------------- If the 270 won't do it the .338 will, if the 338 won't I can't afford the hunt! | |||
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| Moderator |
ground effect has no relevence at any distance higher than 2X "wing" width, and ZERO at supersonic speeds.. a bullet does NOT fly with its nose lightly lighted, nor does it generate ANY lift .. if it did, bullets would arc UP the faster they went yaw -- the nose wandering, DOES happen, but its cyclic.. otherwise it would SPRAWL, and fly like a bottle rocket. IF a bullet was fired with ZERO angle and zero arch (not anything like a useful hunting gun) and a same bullet was dropped, the instant both "cleared" the barrel, they would hit the ground at the same time... since that is a rigged case.. no gun sighted in for 100 yards from anything less than a CLIFF for a shooting station... its of no relevence other than to say gravity is constant. if one drop a bb and a bowling ball, zero forward speed, they both hit the ground at NERLY the same time... as the principal of gravity and stuff hitting the same time, ALSO depends on it being in a vaccum .. the bowling ball is both less dense and has a higher "lift" due to surface area drag, which, in this case, actually provides something like lift against gravity as compared to the BB ... this ONLY worked in the case of dissimular densities, as thats the only way that the law of sqaure cubes doesn't directly apply.. a bb and a cannon ball, of the same metal, the cannon ball would hit slightly FASTER if dropping in the air, as it has less lift .. but this is REALLY picking fly specs if the denesity (and pressure and temp) is the same, when you square the volume you cube the mass ... every time all of the above has NOTHING to do with the question opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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| new member |
Wayfaring Stranger, Sorry I messed up the reply. The first 3 paragraphs of that post are not mine. As for ground effect, I read it a long time ago and as I said, haven't heard it discussed in a long time. As I remember, the slower the bullet, the more it would be effected by passing close to objects or the ground, but even high velocity bullets would be minutely effected | |||
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| Moderator |
I did some research in the 90s on WIG (wing in groundeffect) .. the russians made a HEAVY transport plane .. that used 6 jets to just provide direct UP lift (they were 70 degree down, nonadjustable) besides the score of standard engines .. and like the spruce goose, it could not fly out of ground effect .. it didn't have enough lift ... and distance DOES matter ... you can fly up a mountain in WIG, but down is an instant CRASH ... there's even some flying personal watercraft/boats that can fly 4-8' above the water ... but if you cross an 6' wave, you are now 14' (or 16 due to trowth) and the plane dives... causing pilot to jerk UP, causing plane to stall out of WIG, and SPLASH opinions vary band of bubbas and STC hunting Club Information on Ammoguide about the416AR, 458AR, 470AR, 500AR What is an AR round? Case Drawings 416-458-470AR and 500AR. 476AR, http://www.weaponsmith.com | |||
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