Reply with quote #1
I am getting ready to build a 6mm rifle on a 8 twist barrel. I have read about every thing I can get my hands on about twist rate to bullet weight and what every one seems to think is ideal for some reason or another.
It's obvious that stabilization is necessary, but the term keeps coming up about "Over stabilization" for various twist/weight/ calibers.
Once a bullet reaches stabilization it appears to me that further rotational speed would just "Enhance" stabilization/accuracy unless the bullet/projectile had some inherent reason to not accept that rate of twist do to it's construction or had some mishap during flight.
To "Anyones Knowledge" has there ever been a test performed on a projectile like a "100/115" bullet through the use of a mechanical firing medium with varying twist rate barrels to decide if there is actually an advantage or not to the term of "Over Stabilization"?
Reply with quote #2
HBC has done alot of testing on this, and stated that higher stability with long range bullets is beneficial rather than detrimental.
My take on this for long range shooting, is that another turn won't hurt. But everything has it's limit. Else all barrels would simply be 6 twist, regardless.. That would certainly assure stability right?
Reply with quote #3
Thanks for the reply mike. To answer your question, I don't know. That is part of my reason for posting the question. We here this so often that we naturally conform to the current wisdom on twist rate, regardless of whether it is based on a real study or not, other than "enough twist to stabilize". Somewhere deep inside of my way of thinking this might possibly have some bearing on concepts from bygone days! I could be wrong, but I really don't know! Interesting isn't it when you view it in/at another angle/perspective. I have a strong feeling Mr. Child's is working on the presumption of this concept. Then again, I might be wrong!
Reply with quote #4
Once the bullet is stable, twisting it faster will only start bringing out inconsitencies in the bullet's construction. So any lob-sided lead deposits, air bubbles, jacket thickness, deformed ogive etc will start to wobble the bullet to the point that it can spin off course.
Like when they don't balance your tires out, you will not notice anything until you start going faster, then it will start to vibrate. As the bullet is not held in place like the wheel, it will start to stray from it's path. So it has nothing to do with stability (Sg) as related to twist rate. But more with the anomalies from the physical make-up of the bullet that show up when you spin it at a certain rate. The blow-ups you read about are the extreme example of this.
There are quite a few threads on this forum and over on benchrest.com about this, should you want more details. Henry (HBC) is the man to talk to for all the details.
Reply with quote #5
Dan Lilja has a series of articles concerning accuracy on his website. The one on barrel twist expains, along with the math, the effect of too fast a twist. Interesting reading. I think most of the articles were published in Accuracy mag.