barrel twist rate

[nagarifle]

this makes an interesting read and some good link on the subject

http://www.1728.com/energy.htm

http://kwk.us/twist.html

http://www.stickledown.co.uk/

[brihacharan]

Great info pal. Am much wiser now
Cheers
Brihacharan

[nagarifle]

you must be quick reader

[Motorpsycho]

Am a little confused ,


""when the density of the bullet is less than that of lead or the density of the resisting medium is greater than that of air, the spin should be increased as the square root of the ratio of the densities.""


Since Angular acceleration is inversely proportional to mass. Will A heavier grain bullet will need more twists and muzzle velocity then a lighter grain projectile to have the same spin. Or am I confusing it with inertia

[hvj1]

Am a little confused ,


""when the density of the bullet is less than that of lead or the density of the resisting medium is greater than that of air, the spin should be increased as the square root of the ratio of the densities.""


Since Angular acceleration is inversely proportional to mass. Will A heavier grain bullet will need more twists and muzzle velocity then a lighter grain projectile to have the same spin. Or am I confusing it with inertia

Dear Motorpsycho,

Soon you will get to know Nagarifle,

Beware of brother Nagarifle.
Its his wont, to lay little traps like these,
gigling away with nasty glee,
He tip toes, behind a bushy tree
there he waits with ears alive
Fools like me pretending to be wise
Open our mouths and fall with a crash
Out jumps Naga, howling with joy.
Another idiot is trapped Ahoy!

[MoA]

In principle heavier bullets need faster twists. Velocity in theory is good, but ideal velocity is dependent on application. Long range shooting, BR et al has everyone pushing thierbullets close to or a little over 3000 fps. However a recent 300 M ISSF record was set shooting at an average velocity of aroun 2600 fps.

Ultimately the targets dont lie.. you need to work a 'load' that works in your particular rifle. It is somewhat more complicated than just twist rates and bullet wieghts. Barrel harmonics have a part to play as well, which is why Tuners are becoming very popular right about now.

[nagarifle]

hvj1 your are outdoing yourselfe.

[Motorpsycho]

@ MoA ,

Thanks for the reply ,I guess it's still a black art! I'll have to do a bit of reading to understand it better.

@hvji

The road to knowledge is long and "Twisted"
Once in a while I'll get busted
May fall in his trap and get a little rap
I'll get called a fool ,
For the art of the gun ,it's all cool

[TwoRivers]

To boil it down, the longer the bullet (for caliber), the faster the required twist. Greenhill's Formula is quite simple: 150 times the diameter squared, divided by the length of the bullet, equals the required twist rate. Velocity plays a minor role, and is disregarded.