vibration node Q

[Jeff In TX]

Mikecr,

This is a good subject. I think Jim Ristow understands this particular subject better than most folks. I think Brent will agree. I'm going to copy your orginal post to Jim and see what he thinks. We I get an answer, I'll post it.

[Brent]

I agree. [img]images/icons/smile.gif[/img] Mike and Jim might enjoy conversing too. 888-634-8028 [img]images/icons/wink.gif[/img]

[Jeff In TX]

Mikecr,

Here's Jim Ristows response

1) The barrel moves in what I can only describe as a 3 dimensional wave. The amplitude is of course affected by profile, thickness and length.


2) It is caused by the mass of the bullet being accelerated into a twist. The rate of acceleration and twist determines the frequency.


3) Imagine a smooth bore with all rifle mass in line so there is no muzzle rise. There would be no harmonics just slight "ringing". Two entirely different issues.


4) Shorter and thicker barrels are more rigid with less muzzle movement but it is still there. In practical application the nodes (where it will shoot) are simply wider. A "Whippy" barrel is less tolerant of ES and nodes are narrower.


5) Where the barrel shoots best the muzzle is at the extremity of swing, not at the static location....this is the nugget of info that should bring it all together. You can prove this yourself by loading a long thin barrel to several nodes and shooting at the same 100 yard aim point (utra lights are perfect for this). Often lower velocity nodes will shoot up and to the side. I have seen 9 or 10 inches between groups (most only 4 to 5) which proves at least 4 or 5 minutes of muzzle swing on thinner barrels.

[img]images/icons/smile.gif[/img] Hope this helped

[MAX]

Mikecr, you may be a poor country boy but you ain't no dummy. [img]images/icons/wink.gif[/img]

Harold Vaughn's book, "Rifle Accuracy Facts", covers a number of vibration issues and modes, and may be of some help. If not specifically, perhaps in general.

The discussion above is interesting in regards to the weapons, but don't forget about bullet imbalance. It adds to the chaos. Robert McCoy had a few things to say about that.

[Mikecr]

I'm emailing Jim to see if he can expand on this for me. If his methods are sound, then it could be a real break for me.
Else it's back to the grind!