Will Someone Please Enligten Me?

[cgeorgemo]

http://i3.photobucket.com/albums/y94/cgeorgemo/100_1026.jpg
You will need more twist than 1-14" to stabilize 70gr .224 even at HIGH velocity they tumble...

[stangfish]

Some of them are actually spinning in excess of 250,000 rpm.
Best regards,
Grit


Wow. That is staggering. As an example using a 1:12 twist @ 3000fps. 1 x 3000 x 60. So at the muzzle we have 3000 revolutions per second x 60 seconds. 180,000 rpms. I would have never have believed it until you brought it up.

[thomae]

Bigedp51: Very interesting article. What is the source?

[82boy]

You will need more twist than 1-14" to stabilize 70gr .224 even at HIGH velocity they tumble...

I had a conversation with Randy (RG) Robinette, on gyroscopic stability, twist rates and speed. He told me that bullet speed, will not change bullet RPM enough to gain gyroscopic stability. In laymens terms if you have a 1 in 10 twist 308 shooting a 180 gr bullet at 2850 fps and a 1 in 10 twist 300 win mag shooting the same 180 gr bullet at 3000 fps the rpm change will not be signifinate enought to gain gyroscopic stability. He said even at 1000 fps difference speed wise it is not to change the gyroscopic stability number .01 point. So agin to put it in laymens terms you will not get a 70gr bullet to stabilize in a 1 in 14 twist bullet no matter how fast you spin it, or how fast you push it.

[stangfish]

You will need more twist than 1-14" to stabilize 70gr .224 even at HIGH velocity they tumble...

I had a conversation with Randy (RG) Robinette, on gyroscopic stability, twist rates and speed. He told me that bullet speed, will not change bullet RPM enough to gain gyroscopic stability. In laymens terms if you have a 1 in 10 twist 308 shooting a 180 gr bullet at 2850 fps and a 1 in 10 twist 300 win mag shooting the same 180 gr bullet at 3000 fps the rpm change will not be signifinate enought to gain gyroscopic stability. He said even at 1000 fps difference speed wise it is not to change the gyroscopic stability number .01 point. So agin to put it in laymens terms you will not get a 70gr bullet to stabilize in a 1 in 14 twist bullet no matter how fast you spin it, or how fast you push it.


Well Put 82Boy

Signifinate ;D I hate it when I do that but Love it when you do!

[cgeorgemo]

I had a conversation with Randy (RG) Robinette, on gyroscopic stability, twist rates and speed. He told me that bullet speed, will not change bullet RPM enough to gain gyroscopic stability. In laymens terms if you have a 1 in 10 twist 308 shooting a 180 gr bullet at 2850 fps and a 1 in 10 twist 300 win mag shooting the same 180 gr bullet at 3000 fps the rpm change will not be signifinate enought to gain gyroscopic stability. He said even at 1000 fps difference speed wise it is not to change the gyroscopic stability number .01 point. So agin to put it in laymens terms you will not get a 70gr bullet to stabilize in a 1 in 14 twist bullet no matter how fast you spin it, or how fast you push it.

And yet the 69gr bullets made that nice little 4 shot group with the one flyer way off to the right.
And I did push it. Hard bolt release and even a couple popped primers on those. I cracked my bolt head as well sometime in that session.
http://i3.photobucket.com/albums/y94/cgeorgemo/Bolthead.jpg
Not just the blown out ejector hole but there are cracks around the base of the bolt head where it joins the shaft.

[allan1066]

Here's a great bit of video animation by Brian Litz showing how a bullet settles down after 1-200 yds. Keep and eye on the time and distance travelled.


http://www.youtube.com/watch?v=4pF8W5liSRc&list=UUXHEynBz997rvrIy5cUNFzQ&feature=player_detailpage

[SMK Shoe]

Are you kidding me. Just because some one built some animation trying to prove a bullet is smart and will stabilize the same way each time and become more accurate farther down range. All it would take is a bullet "settling down" a degree or two off then it will "settle down" on a whole different tangent. I am no expert, but have been a artilleryman for 22 years and have never seen a round get more accurate at a farther distance

[allan1066]

Are you kidding me. Just because some one built some animation trying to prove a bullet is smart and will stabilize the same way each time and become more accurate farther down range. All it would take is a bullet "settling down" a degree or two off then it will "settle down" on a whole different tangent. I am no expert, but have been a artilleryman for 22 years and have never seen a round get more accurate at a farther distance


I think you need to delve a little deeper and do some reading on the subject. That animation is not just produced by some kid with a computer. Brian Litz designs rockets for the US military in his spare time.

http://bulletin.accurateshooter.com/2008/08/brian-litz-marksman-rocket-scientist-ballistic-guru/
http://www.appliedballisticsllc.com/Articles.htm

[stangfish]

Are you kidding me. Just because some one built some animation trying to prove a bullet is smart and will stabilize the same way each time and become more accurate farther down range. All it would take is a bullet "settling down" a degree or two off then it will "settle down" on a whole different tangent. I am no expert, but have been a artilleryman for 22 years and have never seen a round get more accurate at a farther distance


::)

[SMK Shoe]

Quote from article
"I learned a lot about epicyclic swerve from this project. The bottom line is that epicyclic swerve cannot cause smaller angular groups at longer ranges. The reason is because it’s so small. The main reason it’s small is because the bullet is precessing (coneing) too fast for the nose to steer the bullet very far off course"

This is a quote from the article that I was told to read from previous post. In the article he states that "if you get a 1.5” group at 100 yards that increases to 3.0” at 200, etc, only 0.03” of that dispersion is due to epicyclic swerve. "

Like I said, I am no expert, but have been shooting everything from 5.56mm thru 205MM ( yes 8 inch, 213lb) projectiles and have taught thousands of soldiers how to shoot M-4's. But I can see how a bullet will settle down farther down range but can't see how it could do it the EXACT way each time to improve accuracy.

[nsaqam]

Like I said, I am no expert, but have been shooting everything from 5.56mm thru 205MM ( yes 8 inch, 213lb) projectiles


The 205mm isn't chump change but it pales in comparison to the 406mm 16" 2700lb projectiles I shot all the time when I was a FC on the USS Iowa! ;D

2700lbs 23 miles is impressive.

[Celtic Warrior]

Like I said, I am no expert, but have been shooting everything from 5.56mm thru 205MM ( yes 8 inch, 213lb) projectiles


The 205mm isn't chump change but it pales in comparison to the 406mm 16" 2700lb projectiles I shot all the time when I was a FC on the USS Iowa! ;D

2700lbs 23 miles is impressive.


But did it wobble?

[SMK Shoe]

I visited the uss north carolina and stood next to a 16". Da@@ it was big. Would not want to have to move one of those between guns. That big of a round hitting base first would still wreck someone's day. May be twice as big in diamiter but weight wise was 10 plus time heavier. Nice to meet another artilleryman ( even if it was navy) ;D ;D ;D ;D

[nsaqam]

I visited the uss north carolina and stood next to a 16". Da@@ it was big. Would not want to have to move one of those between guns. That big of a round hitting base first would still wreck someone's day. May be twice as big in diamiter but weight wise was 10 plus time heavier. Nice to meet another artilleryman ( even if it was navy) ;D ;D ;D ;D


Yeah, those poor Gunners Mates had to slide those things around on an oiled floor to get them in the projectile hoist.
The fatigue suffered by the guys on the projectile deck and around the powder hoist is the reason we couldn't keep up the two rounds per tube every minute for more than 30 to 45 minutes.
They could do one round per tube per minute pretty much indefinitely though.
At the maximum rate of fire however that would mean 48,600 (with the heavy AP projectile, 34,200 with the HE projectile) pounds of ordnance on target every minute!!!
That AP projectile was designed to penetrate 30 FEET of reinforced concrete before detonation!
Just FYI, each projectile was propelled by 660 pounds of powder in six 110 pound silk bags and was ignited by what is essentially a blank .30-06 cartridge.
That old analog FC system was a marvel of gears, cams, shafts, optics, and gyros and it was astonishingly effective.