sabotloader

Big Z

I do not think velocity has anything to do with RPM's that is set in the bore and decays as the bullet travels.... however, velocity will the get the bullet a greater distance before the RPM's decay to instability

I think!

Semisane

Wake up Sabotloader. You're lagging behind the class. Revolutions per distance is set in the bore. Reveloutions per minute is a function of both twist and velocity.

Let's slow everything down. If you shoot a bullet out of a 1:36 twist bore at a velocity of three feet per second, the bullet would travel three feet in a second and revolve once during that second (i.e. 60 RPMs). Now shoot that bullet out of the same bore at 6 feet per second the bullet would travel six feet in a second and revolve twice during that second (120 RPMs). It's still rotating one time for every thirty-six inches traveled, but it's traveling twice as far in one second, so higher velocity means higher RPMs - but still one revolution per 36 inches traveled.

sabotloader

Semi

I thinking....

I did think... i really tried

I'll read this again tomorrow... I am baby sitting my 2 1/2 year old grand daughter all by myself - I am not thinking well when it comes to high math...

Semisane

OK Grandpa. We don't want to distract you from the important stuff.

My youngest granddaughter is seven and her sister is twelve. Delightful ages also, but I wish I could start them over at two again. The twelve year old starred in Samantha's First Turkey (LINK: http://huntingnet.com/forum/black-po...st-turkey.html) What fun they are.

sabotloader

Semi

OK it is new day, the diaper is changed she is dressed and playing in the living room, later we are headed to 'Frog Pond' play area in the mall...

but! I think i have it now... RPM does increase with velocity over a given distance and ROT 'rate of turn in a distance' is set by the twist of the bore - am I getting warm???

UncleNorby

Semi

The way I look at it, the only thing making a bullet spin is the influence of the rifling. Once outside the bore, that influence is eliminated and spin can only diminish. Once started spinning, the bullet does not "want" to spin faster or even keep spinning at all. The RPM and rotation per inch decrease as the bullet travels downrange.

Semisane

And that's why a bullet can be accurate as heck out to a certain distance and then loose accuracy beyond that distance. The closer a bullet is to the necessary rate of twist for stabilization when it's launched, the shorter the distance at which it looses stability and accuracy.

lemoyne

Mike you really can only separate them to a certain extent. I used 160gr of cartridge grade pyrodex in the gun I won every thing with, it had a 40 inch barrel and the velocity was part of what gave me an edge.
I give you the example of my 2400fps load with the Lehigh 200gr 40 caliber bullet shooting 1/2 to 3/4 inch groups when I am shooting good. The length of the bullet and the twist of the barrel and the whip of the barrel control accuracy as long as the velocity allows all to match up. Take the cartridge guns that shoot 4400 FPS and put all the bullets in one hole as an example if speed caused inaccuracy that could not work.
Also the speed of rotation has been checked with marked bullets and high speed cameras the speed of rotation slows very little after the bullet leaves the barrel, and as for it speeding up after it leaves the barrel thats a fairy tale.

Old/New

What is the RPm of the younger granddaughter when she is on her sit & spin?

Does an object in motion tend to stay in motion unless acted on by another force? Just askin'!

Semisane

I can tell you one thing Old/New, if you give the younger one a ten minute nap and a brownie when she wakes you can double her velocity. .