Twist and bullet length

[Lee 9]

Calculated Bullet length for 1-28 and 1-24 twist

Twist 1-28 Twist 1-24
Diameter Bullet length in inches Diameter Bullet length in inches
.458 1.10 .458 1.3
.450 1.05 .450 1.25
.400 .85 .400 1.00

I though some of the newer people might find this interesting. If I made any errors say so.
This would be the ideal length, that does not mean other lengths won't shoot good.
I personally have found that shorter bullet while slightly over stabilized will shoot fine but if the are longer they seem to loose stability.

 

[long shot]

Calculated Bullet length for 1-28 and 1-24 twist

Twist 1-28 Twist 1-24
Diameter Bullet length in inches Diameter Bullet length in inches
.458 1.10 .458 1.3
.450 1.05 .450 1.25
.400 .85 .400 1.00

I though some of the newer people might find this interesting. If I made any errors say so.
This would be the ideal length, that does not mean other lengths won't shoot good.
I personally have found that shorter bullet while slightly over stabilized will shoot fine but if the are longer they seem to loose stability.

Do you have the weights?

 

[Lee 9]

The weight is not need for stabilization, only the length and diameter affect stabilization.

 

[GM54-120]

Velocity matters too. Pittmans long 40cals (1.27"+) for example probably wont shoot in my Super DISC just because i cant shoot them fast enough but they will shoot in a Pacnor 1-22 which can shoot them way faster. A Fury 40cal 250gr is shorter but 25gr heavier. Those should shoot in both my 45s even down to 2000fps or slightly less.

The calculators i normally use list:
Bullet length
Bullet diameter/caliber
Weight...and you should include the sabot weight
Muzzle velocity
Bullet material
1 or 2 include tip length.

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
http://www.bergerbullets.com/twist-rate-calculator/

This one is more basic but appear to be pretty reliable. http://kwk.us/twist.html

 

[long shot]

The weight is not need for stabilization, only the length and diameter affect stabilization.

I understand that. It helps with making a drop chart is what I was getting at.

 

[52Bore]

I use Whitworth's extensive small-bore rifle testing in the early 1850s' as my standard for bullets.
He tested who knows how many bore diameters and twist, some twist rates were as much as 1:1".

When I obtained a 45 1:30 Knight Elite, I used his small-bore 45 1:20 530gr to mathematically calculate the weight of the bullet mold I wanted to make.
1:20 & 530 is to 1:30 & X. Hard to share on the computer (530x20)/30=353. I did the same for length, Whitworth's is 3 bore diameters = 1.35"- So, 20/30=0.667; 1.35"x.667= 0.900" long.

I'll have to look up what the computers says..
I too would think weight is considered as I would think a lighter bullet (same length/design) would require more twist at the same velocity - never thought Greenhill's was absolute.
Interesting Thanks

 

[Dougs136Schwartz]

I thought a lighter bullet took less to stabilize but the heavier bullet once stabilized will hold velosity longer thus will also stay stabilized longer than the light bullet ? You guys are way sharper than I am on this subject I'm just asking .

 

[52Bore]

I thought a lighter bullet took less to stabilize but the heavier bullet once stabilized will hold velosity longer thus will also stay stabilized longer than the light bullet ? You guys are way sharper than I am on this subject I'm just asking .

Correct as I think you're thinking lighter as in shorter, but I didn't type my thought with both bullets being the same length - oops. ex. exact bullets from 2 different materials.
I'll see if I can edit my post.
Thanks

Yep, it let me change

 

[Lee 9]

I thought a lighter bullet took less to stabilize but the heavier bullet once stabilized will hold velosity longer thus will also stay stabilized longer than the light bullet ? You guys are way sharper than I am on this subject I'm just asking .

During the flight time of a bullet the spin which stabilizes it does not change much is my understanding. If the bullet is completely stable to start with then only defects in the bullet will affect the stability however if there is the slightest instability longer range will show it up.
To address the velocity question. Velocity does most certainly affect stability as it changes how fast the bullet spins. How ever I started this thread as a point of interest for some new people and the information is only applicable to black powder and subs used in the normal velocity range of 1600 to 2100 FPS.

 

[52Bore]

How ever I started this thread as a point of interest for some new people and the information is only applicable to black powder and subs used in the normal velocity range of 1600 to 2100 FPS.

Agree.