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August 15, 2012, 11:19 AM | #26 |
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dacaur, go back and read my post again. I think you misread or misunderstood it.
What I said was that with both bullet types being perfect and zero spread in BC, muzzle velocity and atmospheric conditions (nothing in the air changes for all shots fired; it's all constant), both types will shoot with the same accuracy. But the FB bullet's group will be lower on the target than the BT one 'cause it drops more due to its lower BC. |
August 15, 2012, 04:30 PM | #27 |
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This seems to make sense to me, but I'm no engineer. Just seems "logical".
See "First"... http://www.appliedballisticsllc.com/...lletDesign.htm |
August 15, 2012, 08:39 PM | #28 | |
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Quote:
So even with both bullet types being perfect and zero spread in BC, muzzle velocity and with real world atmospheric conditions (as opposed to theoretical) Yes the FB bullet will be lower on the target at 1000 yards, but it will also have much bigger groups, every time, because everthing that has affected the BT bullet on the way to the target, has affected the FB bullet MORE (excluding gravity, of course) |
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August 15, 2012, 08:54 PM | #29 |
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Given equal BC and launch speed of flat base and boat tail bullets there is no advantage in the boat tail bullet's trajectory until after it has dropped below sonic speed.
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August 16, 2012, 09:32 AM | #30 |
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wncchester, what boattailed bullets stay accurate after they've gone subsonic? I'm not aware of any, nor any flat based ones, either.
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August 16, 2012, 03:15 PM | #31 |
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Bart, I wasn't addressing pure accuracy, only the slightly flatter trajectory at the longer ranges after the bullets drop below sonic speeds. But some people translate their inability to properly correct for drop as 'better accuracy' with boattails.
Me, I'm a practical southeastern hunter and I've never detected any predictable differences in accuracy directly due to the form of the base but then I'm really not a long range shooter anyway. I've only been doing this stuff since '65 so I still have a lot to learn! |
August 16, 2012, 03:48 PM | #32 |
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This has been interesting reading. I didn't know the answer, so I hoped that ya'll would come up with one. What I have read over the years, and what I have come to believe (right or wrong) is that a flat base or a boat tail, if constructed equally well, will shoot equally well. However, it seems that a flat base bullet that has a perfect (or nearly perfect base) is easier to produce than a boat tailed bullet with a perfectly tapered base. Because of that, it's more likely that a flat based bullet will leave the muzzle 'squarely', whereas a boat tailed bullet with a less perfect base (or boat tail) will be slightly more inclined to leave the muzzle less than squarely due to unequal gas pressure acting on the imperfect boat tail as the gas and bullet escape the muzzle.
More than likely, today's bullet production quality allows for more perfectly shaped boat tails than in previous years and previous decades, so maybe this is no longer an issue. If so, they should shoot equally well in properly crowned barrels. |
August 16, 2012, 05:00 PM | #33 |
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wncchester, as far as I know, all bullets, regardless of their shape at the back end, change direction somewhat when they go from supersonic to subsonic. That's why Lake City ammo plant quit using Sierra 168's in their 7.62 NATO match ammo; they went subsonic around 800 to 900 yards and accuracy was deplorable at 1000. Sierra's 175 HPBT replaced the 168 and its longer boattail keeps them supersonic through 1000 easily. That's also why the US Army changed to a 173-gr. FMJBT bullet in the 1920's for the .30-06 long range machine gun use; the 150 spitzers in standard ammo too often went subsonic before reaching 1000 and their accuracy wasn't what Uncle Sam wanted.
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August 19, 2012, 06:56 PM | #34 |
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The bullet is only one component of a cartridge and like everything else, if the rifle doesn't like it then accuracy is out the door. I have a Remington 300 win mag that simply does not like ANY boat tail bullet. You have to experiment with all components with each gun to find the best load.
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August 20, 2012, 08:09 AM | #35 | |
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Quote:
On the other hand, there's several companies making centerfire match ammo that shoots great in decent rifles when properly tested by competant people. Lake City Army Ammo Plant's been doing that for decades with their 7.62 NATO match ammo. And Federal's Gold Medal Match stuff been the commercial industry standard for just as long. |
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August 20, 2012, 09:06 AM | #36 |
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So im kind of confused. Bart I hear and agree with everything you are saying but as one person commented before, they thought given the BT and FB at a far range the FB would hold less of a grouping. Besides the obvious drop, would wind resistance not affect the FB because of the streamline capabilities. Even if there is no wind, would there not be resistance in the air on matter how minimal. For instance, an object cutting through water, depending on the streamline capabilities would slow it down but could it slightly change direction? I am unsure but is there not always resistance... besides gravity of course.
Sorry if this is completely wrong, its been a long time since physics in college, im just trying to brainstorm if the poster could in someway be correct. Also could this be tested if you found a way to take a 1000yrd shot indoors, say the largest airport hanger. Would that not eliminate wind? |
August 21, 2012, 06:39 AM | #37 | |
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themaliciousone, bullets in flight won't change direction (other than what gravity and spin drift from gyroscopic precession causes) unless some external force makes them do so. Both flat base and boattail bullets that are perfectly balanced will repeat their trajectories exactly for every shot when muzzle velocity and atmospheric conditions are constant for each. One bullet types group will be at a different location than the other, but both would be the same size. All's well until they slow down and start traveling at the speed of sound. That's when an external force causes problems because all bullets are not perfectly balanced.
Saved some time ago from some web site: Quote:
Start shooting on the range half an hour before sunrise; it's often dead calm then and the air's so still and stable you can see bullet holes in the black at 1000 yards with a decent spotting scope. Last edited by Bart B.; August 21, 2012 at 11:01 AM. |
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August 21, 2012, 08:59 PM | #38 | |
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BTW, the largest hanger in the world is something under 400 yards, and even if one were built 1000 yards long, its going to have windows, which means its going to have temperature variations along the flight path..... |
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August 22, 2012, 06:44 AM | #39 |
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Dacaur, you're right. The air moves around. I like to watch it when its speed is well under 1 mph so I can make adjustments and correct for it. That's the speed range when it's easiest to see the small, subtle changes. Sometimes its hard to decide if its movement changed enough to make a 1/8 minute change on the sights when the air's barely moving.
Unfortunately, one can only see the wind moving in one range band at a time. So one has to decide if they want to see the wind's movement near the target, somewhere between target and you or near you. But it's the wind nearest you that has the greatest effect. It's impossible to observe the wind at all distances at the same time between muzzle and target. And it's harder to see it on cool days compared to warm ones. Last edited by Bart B.; August 22, 2012 at 08:13 AM. |
August 22, 2012, 09:29 PM | #40 |
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I'm not saying you have to see and adjust for it at every part along the flight path, that of course just isnt possible. I'm just saying that its there, and it IS going to affect your bullets flight, and since its not constant like gravity, its going to affect each shot differently, regardless of if its a BT or a FB bullet. Obviously due to its lower B.C., its going to affect the FB bullet more. (A bunch of little random pushes from random directions), which means the FB groups are going to open up faster than the BT groups as range increases. Thats what this whole thread is about....
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