drag, twist, and transonic flight.

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Kenny Wasserburger
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Re: drag, twist, and transonic flight.

Post by Kenny Wasserburger » Fri Apr 23, 2021 7:32 pm

TGC,

Nope this is a PP bullet top ring is the top of the patch, the bottom is where the case mouth was on the bullet I believe.

You can just barely see it on this recovered bullet that didn’t hit steel. I believe it’s gets stretched upon impact and is more pronounced.



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mdeland
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Re: drag, twist, and transonic flight.

Post by mdeland » Fri Apr 23, 2021 8:53 pm

I guess I have never actually thought of the bullet nose tracking with the trajectory but had it in my imagination as traveling pretty much parallel to the line of muzzle exit and when curving back to earth remaining more or less parallel to exit path. I think I got the idea from watching a foot ball pass that seems to float more or less level as it spirals and drops to a receiver.
I played defensive half back in high school football and had to break up a lot of passes I could not intercept. Boy that was fun in my junior and senior year! Finally made first string for two seasons after riding the bench since the 7th grade! :lol:

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Re: drag, twist, and transonic flight.

Post by Aviator » Fri Apr 23, 2021 9:22 pm

bruce m wrote:
Fri Apr 23, 2021 6:57 pm
mdeland wrote:
Fri Apr 23, 2021 6:32 pm
Interesting how the nose tracks with the trajectory path rather than staying parallel with the initial path.
mike,
you make the point of the original post.
in fact this bullet has a stability of well over the accepted optimum of 1.5 at 2.75, yet still obviously traces.
it will of course be a little nose high to the trajectory curve.
when zeroed at 1760 yds it will have a drop of about 25.6 moa from 1700 yds to 1800 yds.
given that 1 degree is 60 minutes, this is less than 1/2 a degree.
that is for a straight line, while the trajectory curve is more parabolic so would in fact be a little steeper at point of impact.
bruce.
Not quite sure I follow you.
While the come-up in sight setting from 1700 yards to 1800 yards is about 26 minutes of angle, this is not the angle of the bullet trajectory. It looks to me as though the bullet will be dropping roughly 38 feet between 1700 and 1800 yards, which correlates to an angle of about 7.2 degrees.

bruce m
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Re: drag, twist, and transonic flight.

Post by bruce m » Fri Apr 23, 2021 10:29 pm

yes i might be wrong and have done the incorrect calculation.
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Don McDowell
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Re: drag, twist, and transonic flight.

Post by Don McDowell » Sat Apr 24, 2021 6:39 am

15 or 20 years ago Mike Venturino took some bpcr's to a military base somewhere, and they used the radar to track bullets fired from a number of different rifles out to long distance. He wrote the article up in either Guns and Ammo, or Rifle magazine, don't remember which now. The findings they got from that study was pretty interesting and relavant to this discussion.
One thing I keep thinking back to when the comparison to airplane flight etc that always seems to get glossed over is turbulence from wind sheers, thermals etc. that same stuff will affect a bullet as well.
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Re: drag, twist, and transonic flight.

Post by desert deuce » Sat Apr 24, 2021 11:59 am

Wind Shears...........from my observations are most likely the paradox of determining the effects of conditions on bullet deflection. They most likely dramatically affect bullet flight to the target that are the unseen in conditions.

EXAMPLE: 1,000 yard line Raton Nationals. Shooting next to Dan Theodore. We both fire at our respective targets and have center hits. Reload and neither Dan or I nor our spotters discern any change in conditions. We fire again and Dan's shot and my shot hit far short of the target by about the same distance. We actually discuss this and agree to fire the next shot without sight adjustment and both shots are center hits. We later conclude that the only plausible explanation is wind shear driving our bullets to earth.

A vortex or dust devil operating above the tops of the flags yet in the bullet path can also play hob with score. If you see a flag go straight up and twist that was probably the cause. Whiplash in the mirage I suspect is also an indication of this type of disturbance.

Wind Shears and Vortices may also operate between flags and the only indication of their presence is the bullet strike at the target. Phoenix in particular on nice moderate to light wind days that warm quickly can provide mysterious bullet strikes so don't assume a bad bullet or load for the miss. I believe I witnessed Cliff Gregg and Mark Schuenke get caught in a spate of these during a Creedmoor Cup at Phoenix several years ago to the detriment of their scores. The thinking here is you cannot compensate for what is unseen.
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Re: drag, twist, and transonic flight.

Post by mdeland » Sun Apr 25, 2021 1:41 pm

It's pretty obvious the bullet is orientated nose down at quite an angle when it struck steel (assuming the target is vertical and not angled). This was a surprise to me. I had though it would have still impacted target more or less level point on.
My competitive experience has only been to midrange distance (600 yards) and I never noticed oblong bullet holes through the target indicting angular bullet orientation.

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Re: drag, twist, and transonic flight.

Post by bruce m » Tue Apr 27, 2021 1:47 am

desert deuce wrote:
Sat Apr 24, 2021 11:59 am
Wind Shears...........from my observations are most likely the paradox of determining the effects of conditions on bullet deflection. They most likely dramatically affect bullet flight to the target that are the unseen in conditions.

EXAMPLE: 1,000 yard line Raton Nationals. Shooting next to Dan Theodore. We both fire at our respective targets and have center hits. Reload and neither Dan or I nor our spotters discern any change in conditions. We fire again and Dan's shot and my shot hit far short of the target by about the same distance. We actually discuss this and agree to fire the next shot without sight adjustment and both shots are center hits. We later conclude that the only plausible explanation is wind shear driving our bullets to earth.

A vortex or dust devil operating above the tops of the flags yet in the bullet path can also play hob with score. If you see a flag go straight up and twist that was probably the cause. Whiplash in the mirage I suspect is also an indication of this type of disturbance.

Wind Shears and Vortices may also operate between flags and the only indication of their presence is the bullet strike at the target. Phoenix in particular on nice moderate to light wind days that warm quickly can provide mysterious bullet strikes so don't assume a bad bullet or load for the miss. I believe I witnessed Cliff Gregg and Mark Schuenke get caught in a spate of these during a Creedmoor Cup at Phoenix several years ago to the detriment of their scores. The thinking here is you cannot compensate for what is unseen.
zack,
we all know wind shears exist or if we don't will find out one day.
understanding what happens in that process might help minimize problems caused.
possibly some of us have different definitions of what a wind shear.
mine is when a bullet goes through a change of wind direction of a sudden nature.
a bullet in flight in a consistent condition is stable because all the forces acting on it come into balance, and the bullet ceases to go through precession and nutation, settling into the yaw of repose, nose a little high and to the right for a rh twist.
when the pressure of the wind increases or decreases the balance of wind pressure, gravity etc changes.
with this the yaw of repose changes.
in extreme cases the bullet can go back into precession and nutation prior to becoming stable again.
while all this is going on, the bullet is steering itself throught the air like a canoe in water.
it tries to go where it is pointing, and the more it points in different directions, the more it goes in different directions.
doing all you can to improve stability will minimize this, and that is speeding up the twist.
if you cannot eliminate it altogether, you still might get a hit on the target where a less stable bullet will go over the top or god only knows where else.
bruce.
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Distant Thunder
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Re: drag, twist, and transonic flight.

Post by Distant Thunder » Tue Apr 27, 2021 6:40 am

"...doing all you can to improve stability will minimize this, and that is speeding up the twist."

Or you could just shoot a bullet that is short enough to be WELL stabilized in the twist rate you have! Just a thought. :D

Also, the nose design plays a part in the stability for a given twist rate and choosing a good design will help. Choose wisely! A good nose design can in and of itself deal with wind shear better than a poor one.

With many .45 caliber rifles with 1-16 twist rates that can do well with longer bullets with long pointy noses many shooters with a 1-18 twist mistakenly think they can shoot the same bullets in their rifles with the same results and they can NOT.

You can rebarrel to a faster twist, buy a new rifle with a faster twist or buy one of those rifles with an adjustable twist barrel that you can set to the best twist for the conditions you have that day. I prefer to tailor my bullets to my rifle's twist rate and chamber configuration then spend the time shooting to learn how that combination reacts in various conditions and adjust accordingly. Custom molds while not cheap are still less expensive than custom rifles and the wait times are less.

Either method can work.
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desert deuce
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Re: drag, twist, and transonic flight.

Post by desert deuce » Tue Apr 27, 2021 8:40 am

A barrel with an adjustable twist rate? buy one of those rifles with an adjustable twist barrel, and where would one find such or do you mean a gain twist barrel?

I suspect a shooters perception of the conditions that affect the flight of the bullet are influenced by their shooting experience at the ranges they shoot on. Some ranges are arranged so that the flags in particular are helpful. One range I shoot on from 1,000 yards the visual line of sight is considerably over the tops of the flags. Ranges like Phoenix and Raton can be full of surprises. Byers is it's own ball of wax. The situation at Phoenix is that you can experience both down and up drafts on the same relay which are particularly hard on scores when they are from 12;00 O'Clock, mostly because they are unseen. I think about these as waves at the sea shore, up at one point and down at another as they travel along the surfaces of the range much as waves move along the shore. Sometimes below the flags.

It does seem that increasing twist rate, shortening bullet length, adjusting the nose shape, adjusting the weight distribution can reduce the effects the conditions apply to the bullet in flight. Chip Mate for instance shot a 450 grain bullet in his 45-90 at Phoenix this last March quite successfully. I am not talking about the difference between an X and a miss, more the difference between a miss and a 6 or maybe even a 7 at 1,000 yards is, in my opinion, worthy of pursuit. Today that appears to be, for a .45-90, a 16 twist, bullet less than 1.5" long, 16 or harder alloy and a well nourished money style nose to start with.

Thermals whether combined with up or down drafts or not are another matter altogether. I won't mention false mirage.
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desert deuce
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Re: drag, twist, and transonic flight.

Post by desert deuce » Tue Apr 27, 2021 8:42 am

Forgot to mention a grease groove bullet, I am not a source for the use of paper patched bullets for long range.
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Re: drag, twist, and transonic flight.

Post by mdeland » Tue Apr 27, 2021 12:13 pm

I was thinking the ole Postell was a pretty good nose design after all with the addition of mini grooves in leu of standard ones. I have that mold but still mostly use the PJ 510 Creedmoor and I also like the Schmitzer bullet for clang and bang. The irony is that pointy bullet gave me the best scores I have had in midrange competition and at the 600 yard line.

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Re: drag, twist, and transonic flight.

Post by Distant Thunder » Tue Apr 27, 2021 12:43 pm

I did not mean a gain twist barrel, but rather something akin to the oceanfront property I've heard of being for sale in Arizona. Or something on the order of the perfect bullet that so many search for.

With either or both of those two a shooter would not have to put in the range time and learn how a given bullet of a certain length from a certain ROT reacts to the various conditions. They could just shoot through almost anything and never stray too far from the center.

While I have from time to time talked about the superiority of the paper patch bullet and I may have even steered some in that direction I remain strongly convinced that there are some shooters, who I will not name, that should stay as far away from paper patching as possible. Just stay in your lane.
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Re: drag, twist, and transonic flight.

Post by SFogler » Wed Apr 28, 2021 5:54 pm

I watched the YouTube video on Powderburner's page three post. Very interesting and then I watched the same guy on Smarter Everyday go for a supersonic ride in an F-16. Having been there, the guy is right - nothing happens - no shudder, shakes, twitches; you see the Mach indicator going to 1.1 Mach but no vibrations etc. But what is interesting is the altimeter goes nuts as the static pressure on the holes in the side of the pitot tube changes with the shock wave travel from subsonic to supersonic to subsonic again as they speed up then slow down. I don't know if that would have any effect on the bullet in the conditions we shoot them.

If you fast forward to 11:00 and watch till 15:30 you will see the altimeter beside the Mach indicator go nuts while the Mach indicator smoothly goes from .99 to 1.1 and back down again. He also gives an good explanation using a model pitot tube that looks surprisingly like a big bullet to describe the static pressure effects. I'm no physics major - I just pulled on the stick and the houses got smaller - pushed on the stick and they got bigger. And I shoot my loads till the holes get closer. But it's good to find out what the man behind behind the curtain is up to.

https://www.youtube.com/watch?v=p1PgNbgWSyY

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Re: drag, twist, and transonic flight.

Post by mdeland » Thu Apr 29, 2021 6:00 pm

Remember how the x-1 Yager broke the sound barrier in was buffeted almost out of control just before going through Mach.
The shaping of wings, tail and fuselage is what makes it possible in high speed aircraft which by the way is not spinning at 100K rpms.
Our square based level sided bullets have no such design advantage to stabilize them only the nose shape, center of gravity,center or pressure and rotational spin.

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