Understanding bullet stability value
- Thread starter Wis65x55
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jimbires
Handloader
- Aug 16, 2011
- 3,151
- 1,855
I'm not sure I understand all there is to this . under stabilized can cause a bullet to tumble . slightly under stabilized will allow the bullet tip to yaw (wobble ) . grossly over stabilized can cause a bullet to come apart . slightly over stabilized can help a bullet transition into transonic better . over stabilized will cause more spin drift . it's a balancing act . I would rather be a little over stabilized , than under stabilized . bullet length , velocity , altitude , all come into play here .
here's a couple links on this .
https://bergerbullets.com/the-state-of- ... stability/
https://bisonballistics.com/articles/bullet-stability
here's a couple links on this .
https://bergerbullets.com/the-state-of- ... stability/
https://bisonballistics.com/articles/bullet-stability
mjcmichigan
Handloader
- Dec 26, 2016
- 2,342
- 218
What Jim said.
You get group sizes that are a function of bullet stability plus the harmonics of your load in your rifle, plus stability in muzzle velocity.
Stability is one factor of several you need to think about if you are not happy with the size of your group.
For instance.. my 22-250 REM, 1:14 twist
Stabilizes 40 grain bullets like no tomorrow.
Can get bug eyed clover leafs. If I got up to 50gns, most my loads are 1”, if I go to 55 gns
The groups open up more..
That said, I have friends on the forum their 1:14 twist 22-250 stabilizes a 50 gn fine.
So the stability calculator is theoretical.
Just like a lot of cup and core bullets like a ‘0.02” jump, and mono’s and bonded bullets like Jump greater that 0.05”.
Another guideline after a long answer.
Sent from my iPhone using Tapatalk
You get group sizes that are a function of bullet stability plus the harmonics of your load in your rifle, plus stability in muzzle velocity.
Stability is one factor of several you need to think about if you are not happy with the size of your group.
For instance.. my 22-250 REM, 1:14 twist
Stabilizes 40 grain bullets like no tomorrow.
Can get bug eyed clover leafs. If I got up to 50gns, most my loads are 1”, if I go to 55 gns
The groups open up more..
That said, I have friends on the forum their 1:14 twist 22-250 stabilizes a 50 gn fine.
So the stability calculator is theoretical.
Just like a lot of cup and core bullets like a ‘0.02” jump, and mono’s and bonded bullets like Jump greater that 0.05”.
Another guideline after a long answer.
Sent from my iPhone using Tapatalk
- Thread starter
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mjcmichigan
Handloader
- Dec 26, 2016
- 2,342
- 218
Really the two articles Jim put links out there are excellent for helping understand it.
Seems like you’d like a hard and fast rule, that exact point of instability
Is a function of many things…not easily translated into a couple numbers for a bullet stability calculator. I think my 22-250 example with a 1:14 twist and 50 grain bullets was typical. Said it was marginal, some guys are getting it to work in their guns, didn’t in mine… I had 750 50gn NBT so I wanted to make it work… well, my 223 rem is 1:9 and it stabilizes the 50m’s fine.
Basically if it’s close to marginal ie on the Berger stability calculator.. I move on to a better bullet choice… vs spend a lot of effort to make something trying to stay on a razor thin edge of stability.
Sent from my iPhone using Tapatalk
Seems like you’d like a hard and fast rule, that exact point of instability
Is a function of many things…not easily translated into a couple numbers for a bullet stability calculator. I think my 22-250 example with a 1:14 twist and 50 grain bullets was typical. Said it was marginal, some guys are getting it to work in their guns, didn’t in mine… I had 750 50gn NBT so I wanted to make it work… well, my 223 rem is 1:9 and it stabilizes the 50m’s fine.
Basically if it’s close to marginal ie on the Berger stability calculator.. I move on to a better bullet choice… vs spend a lot of effort to make something trying to stay on a razor thin edge of stability.
Sent from my iPhone using Tapatalk
jimbires
Handloader
- Aug 16, 2011
- 3,151
- 1,855
I agree with what Mark said in the post above this one , I'm not sure there is a perfect number . the stability number will change due to weather conditions , elevation , etc . you need to have enough to keep your combo out of trouble in varying conditions . I would not want something that's at the 1.5 , it could go bonkers to easy .
hunting conditions , I think a little faster twist barrel would kill better too . more bullet rpm's
I ran my 338 Lapua through the Berger stability calculator . found at this link .
https://bergerbullets.com/twist-rate-calculator/
if you want to see how my combo works out here's my info , you can fill in the blanks and play around changing velocity , temp , and elevation . I've shot this out to 2375 yards . I had good bullet impact marks on the target , making me think the bullets are stabile at this distance . when I rebarrel this , I think I'll put a 9 twist on .
Berger 300 gr Elite Hunter ( choosing this fills in caliber , weight , length , BC )
velocity 2939 FPS
10 twist bbl .
elevation where we shoot about 1840 ft
you'll see at 0*F I'm at the 1.59
if I get my 2939 velocity , which I doubt I can . cold will lower my velocity , and I'll be not stabilized .
at 90*F I'm at 1.90
a couple guys I shoot with are buying components they can find , not what they are normally using . last weekend when we went out to paint the targets , the 2000 yard target had a couple impacts that were key holes , the bullet hit the target sideways . it left marks that were a perfect profile of the bullet . I wish I had my camera .
hunting conditions , I think a little faster twist barrel would kill better too . more bullet rpm's
I ran my 338 Lapua through the Berger stability calculator . found at this link .
https://bergerbullets.com/twist-rate-calculator/
if you want to see how my combo works out here's my info , you can fill in the blanks and play around changing velocity , temp , and elevation . I've shot this out to 2375 yards . I had good bullet impact marks on the target , making me think the bullets are stabile at this distance . when I rebarrel this , I think I'll put a 9 twist on .
Berger 300 gr Elite Hunter ( choosing this fills in caliber , weight , length , BC )
velocity 2939 FPS
10 twist bbl .
elevation where we shoot about 1840 ft
you'll see at 0*F I'm at the 1.59
if I get my 2939 velocity , which I doubt I can . cold will lower my velocity , and I'll be not stabilized .
at 90*F I'm at 1.90
a couple guys I shoot with are buying components they can find , not what they are normally using . last weekend when we went out to paint the targets , the 2000 yard target had a couple impacts that were key holes , the bullet hit the target sideways . it left marks that were a perfect profile of the bullet . I wish I had my camera .
