Quoted:


Weight added can change the spacing or position of nodal points along the barrel which are crudely defined as fulcrum points at which waves begin and end as they vibrate along the barrels length.  That can cause a light barrel that normally has a certain muzzle orientation in its harmonic vibration pattern when the bullet leaves the muzzle crown, to assume another orientation- this will cause impact shift.  



In my opinion weight is the lesser impacting variable of the two largest variables since barrels are typically not extremely thin.  



The larger concern is eccentricity of the blast baffle aperture and/or other elements of the parts composing the suppressor bore.  Eccentricity causes gas to negatively impact stability of the bullet in much the same way as a bad muzzle crown can.  In eccentric suppressor to barrel bore relationship, the bullet is being pushed with some vector force 90 degrees to the bore axis and simultaneously its stability is being reduced.  That can cause groups to open and point of impact to shift as well as long range projectile drop to increase because increased parasitic drag from less stable projectile flight causes projectile velocity to decrease prematurely.  



Some suppressor mounting systems cannot help but cause shift to some extent.  Many QD mounting systems have course threads or bayonet mounting that leaves the suppressor hanging off the mount with some degree of eccentric relationship.  Other baffle systems may be shear cut in such a way as to impose an oval shape to the bore- in other words they cause a perfectly concentric bore to behave like a eccentric bore on account of gas flow centering at a point off axis of the center of the suppressor bore.

Quoted:
Weight added can change the spacing or position of nodal points along the barrel which are crudely defined as fulcrum points at which waves begin and end as they vibrate/ocillate along the barrels length.  That can cause a light barrel that normally has a certain muzzle orientation in its harmonic vibration pattern when the bullet leaves the muzzle crown, to assume another orientation- this will cause impact shift.  

In my opinion weight is the lesser impacting variable of the two largest variables since barrels are typically not extremely thin.  

The larger concern is eccentricity of the blast baffle aperture and/or other elements of the parts composing the suppressor bore.  Eccentricity causes gas to negatively impact stability of the bullet in much the same way as a bad muzzle crown can.  In eccentric suppressor to barrel bore relationship, the bullet is being pushed with some vector force 90 degrees to the bore axis and simultaneously its stability is being reduced.  That can cause groups to open and point of impact to shift as well as long range projectile drop to increase because increased parasitic drag from less stable projectile flight causes projectile velocity to decrease prematurely.  

Some suppressor mounting systems cannot help but cause shift to some extent.  Many QD mounting systems have course threads or bayonet mounting that leaves the suppressor hanging off the mount with some degree of eccentric relationship.  Other baffle systems may be shear cut in such a way as to impose an oval shape to the bore- in other words they cause a perfectly concentric bore to behave like a eccentric bore on account of gas flow centering at a point off axis of the center of the suppressor bore.

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so whats with that?