Perfect stability factor

[MOOSE39465]

Good evening everyone. After spending tons of money on bullets, and only coming up with marginal accuracy i'm constantly scratching my head as to why a certain bullet shoots better then others. I understand barrel harmonics along with proper bullet stability, and many other things determines accuracy. My question is what is the perfect stability factor for a given bullet? I read that an SG of 1.5 or greater is acceptable for proper bullet stability, but there's got to be a sweet spot above an SG of 1.5 that is optimum. Whats your thoughts?

 

[elkaholic]

Good evening everyone. After spending tons of money on bullets, and only coming up with marginal accuracy i'm constantly scratching my head as to why a certain bullet shoots better then others. I understand barrel harmonics along with proper bullet stability, and many other things determines accuracy. My question is what is the perfect stability factor for a given bullet? I read that an SG of 1.5 or greater is acceptable for proper bullet stability, but there's got to be a sweet spot above an SG of 1.5 that is optimum. Whats your thoughts?

It depends greatly on distance! The farther you shoot, the more you need higher stability. Marginal stability will often shoot equally well at 100 yards but certainly not at 1000 or more.

 

[MOOSE39465]

It depends greatly on distance! The farther you shoot, the more you need higher stability. Marginal stability will often shoot equally well at 100 yards but certainly not at 1000 or more.

Good point. Lets say optimum accuracy to 1000 yards. my longest shots are 850.

 

[elkaholic]

Good point. Lets say optimum accuracy to 1000 yards. my longest shots are 850.

There are many reasons other than stability as to why one bullet is more accurate than another. most have to do with concentricity, uniformity, design, and even barrel preference. I would look for something that would provide good accuracy (stability) at the maximum range you will be shooting. You could use a number as a guideline to get started (say 1.70) but only testing will give you the final answer. Also, some bullets expand better with higher stability, so you need to figure that in as well. i.e. target could be a little different than hunting.
Lots of variables to consider!

 

[Buck Fever]

I was talking to a guy who would use a tool that I forget the name of to spin up bullets and detect if their center of gravity was off of the bullet centerline. You would think with a consistent lead core and jackets with very consistent wall thickness that the differences would be minor but this sorting was enough to see results on target.

So the answer is that everything is why certain bullets shoot better than others.

Stability is a part of it but doesn't seem to do much after you make sure your bullets are well stabilized. I would be much more concerned about the bullet consistently engaging the rifling straight on.

 

[MOOSE39465]

There are many reasons other than stability as to why one bullet is more accurate than another. most have to do with concentricity, uniformity, design, and even barrel preference. I would look for something that would provide good accuracy (stability) at the maximum range you will be shooting. You could use a number as a guideline to get started (say 1.70) but only testing will give you the final answer. Also, some bullets expand better with higher stability, so you need to figure that in as well. i.e. target could be a little different than hunting.
Lots of variables to consider!

Thanks for your input. Unfortunately my time is limited so you know how that goes. My online research is filling that gap right now haha

 

[MOOSE39465]

I was talking to a guy who would use a tool that I forget the name of to spin up bullets and detect if their center of gravity was off of the bullet centerline. You would think with a consistent lead core and jackets with very consistent wall thickness that the differences would be minor but this sorting was enough to see results on target.

So the answer is that everything is why certain bullets shoot better than others.

Stability is a part of it but doesn't seem to do much after you make sure your bullets are well stabilized. I would be much more concerned about the bullet consistently engaging the rifling straight on.

You would think a well built rifle, proper component selections, and proper reloading practices would be enough to obtain sub moa accuracy all of the time, but that's not always the case. I have a few factory rifles that will out shoot my customs. You just never know.

 

[elkaholic]

You would think a well built rifle, proper component selections, and proper reloading practices would be enough to obtain sub moa accuracy all of the time, but that's not always the case. I have a few factory rifles that will out shoot my customs. You just never know.

Kind of like women. You can treat one exactly like another and get a totally different result.
From a womans perspective, I suppose you could say the same about men,

 

[MOOSE39465]

Kind of like women. You can treat one exactly like another and get a totally different result.
From a womans perspective, I suppose you could say the same about men,

Lol. Your right about that 100. %

 

[Mikecr]

Bullets don't get more stable than fully stable (Sg1.5).
This, even while relative Sg goes up significantly, very quickly, downrange.

The highest overturning moment(which Sg overcomes) is muzzle release. And if your bullet is released with an Sg of 1.5, that number will climb from there onward. Marginal stability (1.3) can hurt you in that a bullet may take a bit longer to recover from ugly muzzle release. Longer being maybe 10yds, but that's enough to affect long range results.
Unstable (<1.0) will immediately tumble.

Another factor is dynamic stability. This cannot be calculated nor predicted. It has to be tested for, and normally comes into play at the next biggest stability challenge (transonic region).

It's important to understand what twist requirements mean to stability. Notice they're stated in displacement per turn, like 8":1T. That displacement is relative to a standard air density, and actual distance per turn downrange.
So as atmospheric conditions change, so does your stability.
If you want full stability, you will account for this.

 

[dfanonymous]

The stability factor being talked about is really a transonic issue. If you read that on bergers website or through Bryan litz's books, it's said that the 1.5 stability factor is to make sure the bullet is stable using in reference to specific type of bullets maintaining stability from transonic to subsonic. If you don't shoot in that range, ie; 1000y or less, this level of stability in unwarranted. As long as you have a marginal stability, and are supersonic, you will be fine out to 1000y.

As to why your having issues, I have no idea. It could be you, your technique, bad dope, bad rifle, bad scope, bad loads.
But unlikely a stability issue.

 

[Buck Fever]

You would think a well built rifle, proper component selections, and proper reloading practices would be enough to obtain sub moa accuracy all of the time, but that's not always the case. I have a few factory rifles that will out shoot my customs. You just never know.

Well, things that get missed often are cutting the chamber neck to fit the brass or cutting the brass to fit the chamber neck, cutting the throat to match the bullet and COAL. Most people just go with the chamber they get which has a neck sized to swallow any brass you find, brass from box ammo or bought for price and a throat designed to avoid overpressure.

It's surprising that any guns are accurate with a situation like that.

 

[MOOSE39465]

Bullets don't get more stable than fully stable (Sg1.5).
This, even while relative Sg goes up significantly, very quickly, downrange.

The highest overturning moment(which Sg overcomes) is muzzle release. And if your bullet is released with an Sg of 1.5, that number will climb from there onward. Marginal stability (1.3) can hurt you in that a bullet may take a bit longer to recover from ugly muzzle release. Longer being maybe 10yds, but that's enough to affect long range results.
Unstable (<1.0) will immediately tumble.

Another factor is dynamic stability. This cannot be calculated nor predicted. It has to be tested for, and normally comes into play at the next biggest stability challenge (transonic region).

It's important to understand what twist requirements mean to stability. Notice they're stated in displacement per turn, like 8":1T. That displacement is relative to a standard air density, and actual distance per turn downrange.
So as atmospheric conditions change, so does your stability.
If you want full stability, you will account for this.

Great read thanks for your input. After playing with the Berger twist calculator the last couple of weeks I now understand better how conditions will change, and bullets at 50 degrees will have an certain SD compared to 100 degrees. Which is why I was asking for a optimum stability factor that would cover all conditions. When you live in Mississippi you never know what the conditions are gonna be hour to hour haha

 

[MOOSE39465]

The stability factor being talked about is really a transonic issue. If you read that on bergers website or through Bryan litz's books, it's said that the 1.5 stability factor is to make sure the bullet is stable using in reference to specific type of bullets maintaining stability from transonic to subsonic. If you don't shoot in that range, ie; 1000y or less, this level of stability in unwarranted. As long as you have a marginal stability, and are supersonic, you will be fine out to 1000y.

As to why your having issues, I have no idea. It could be you, your technique, bad dope, bad rifle, bad scope, bad loads.
But unlikely a stability issue.

Thanks for the input. Not really having issues, but I am trying out different bullets. One bullet i'm getting sub moa and the other bullets I get worse result. All bullets gets the same chance various powders, primers, seat depths etc...