Bullet Stabilization

[Mike McBride]

On a few threads I have seen references to bullets that are not accurate until they get downrange and “stabilize”. It seems that; if a bullet is off target at 100 yards, it just gets further off the farther it goes.

I am sure we have all seen slow motion video of arrows launching from bows, but this is not the same system and while those arrows wiggle like a pole dancers the trajectory of the arrow is still a smooth arc. They do not turn and then get back on course, though sometimes they do seem to penetrate deeper from 25 yards than 15. I have no evidence to back that up other than how hard I grunt to pull the arrow.

So, is there any evidence that a bullet is more stable or accurate 400 yards downrange than it is at the muzzle? If my rifle groups 2 MOA at 100 yards, should I expect it to group 1 MOA at 1000?

 

[clmayfield]

Re: Bullet Stabilization

I haven't seen a rifle that will group tighter at longer distances, but I think it is all relative. Some bullets seem to hold accuracy better over range.

I am sure there are anecdotes of tighter groups at longer range than shorter range. On average, though, I don't think there are many cases where accuracy improves at distance.

The only explanation of how this might happen is the helical travel of the bullet might introduce more dispersion at close range where that relative dispersion in insignificant at long ranges.

Accuracy is relative. A 50 BMG is notoriously inaccurate at short range, and yet maintains that accuracy so that it might get outshot by a 308 at 100 yards, but shine at 1,000. All it has to do is start at .75 MOA at 100 yards and go to 1 MOA at a thousand.

 

[aloreman]

Re: Bullet Stabilization

open up your reloading manuals and read the boring pages

 

[gimpy]

Re: Bullet Stabilization

I was actually having this discussion with the chair of the Physics dept at my school, and he believes that it could stabilize with a little distance seeing that air is fluid, but I'm not sure that accuracy would improve per se.

 

[Temp9]

Re: Bullet Stabilization

The reason I've heard for angular accuracy improving at range (ie. 1MOA at 100 yards, .75MOA at 300 yards) is that the bullet's spin causes it to fly in a roughly helical motion around it's ideal path. Eventually, the bullet "goes to sleep", centering in the ideal flight path, and thus having a greater chance of impacting nearer (angularly) to the POA. I don't buy it, personally, but that's what I've heard.

 

[Mike McBride]

Re: Bullet Stabilization

Gentlemen,

Can you be a little more specific on the reading material? All my manuals are quite dated, but I did read article sections of them all (all being Speer, Hornady, and Sierra) way back when I bought them. I am sure any mention of such effect would have stuck in my mind.

Don't get me wrong. I fully understand the analogy of the big 50 where one rifle system may begin less precise than another yet retain its relatively small margin of error where the other has an ever widening angle of uncertainty. That is not what I ponder.

I have read a few remarks that suggest that the stability of the bullet improves with increased range and imply the cone of uncertainty actually may decrease. This seems counter intuitive to my mind. Of course my intuition has proven wrong on countless occasions. My aim is not dispute. I would just like something to get my brain around before it can accept the concept.

The idea of a bullet trajectory following a helix is also new to me. The center of mass would have to spin eccentrically about the path it follows. Maybe an unsymmetrical bullet or one launched with a lot of yaw? In either event it seems the helix would widen rather than tighten.

 

[clmayfield]

Re: Bullet Stabilization

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Gimpy</div><div class="ubbcode-body">I was actually having this discussion with the chair of the Physics dept at my school, and he believes that it could stabilize with a little distance seeing that air is fluid, but I'm not sure that accuracy would improve per se.</div></div>

Exactly. A bullet that is off course is not going to stabilize and then magically know where the original course is and find it again.

But sure, a bullet could stabilize itself during flight. At that point, it wouldn't get more accurate, it would just stop getting less accurate.

 

[bricktop]

Re: Bullet Stabilization

Litz's book has some discussion on this (at least my first edition does). Worth a read...

 

[Mike McBride]

Re: Bullet Stabilization

I can buy that. I wonder if this is the exception or the rule?

 

[Lowlight]

Re: Bullet Stabilization

it's you and not the bullet... the bullet is stupid, it is either stable or it is not, and that happens right out of the bore, CoryT has the details, something like 30 bullet lengths.

What happens is the shooter can shoot better by not seeing the impact versus seeing the impact and mentally screwing himself.

I have yet to see evidence of someone putting a target at 100 yards and a target at 300 yards and showing a bad group at 100 and a good group at 300... until that is demonstrated, it's the shooter.

 

[aloreman]

Re: Bullet Stabilization

Read the interior ballistics section and exterior ballistics section in your seirra manual