Reply To: Why does the POI change with a Moderator on?

Forums Field Target Field Target Talk Why does the POI change with a Moderator on? Reply To: Why does the POI change with a Moderator on?



“fe7565”SDellinger, yes barrel harmonics plays a part too. But (if I understand it correctly) that’s not the same as the pellet traveling over (or exiting from) uneven surfaces like a crown…but more a result of the vibrations/resonance created by the air and pellet traveling through and leaving the barrel..

Anything you attach to the barrel, will affect the harmonics.  Browning’s BOSS muzzle brake, as an example, was adjustable to take advantage of this property.  One would make it a bit longer or shorter to dampen the harmonics so that the bullet would exit when the muzzle was either at the top or bottom of the vibration, thus increasing it’s precision.   Sights, still, have to be adjusted accordingly after the group size is minimized.

The only time a moderator would not affect the point of impact (due to barrel harmonics) is if it were a shroud that was part of the breach and the barrel makes no contact what-so-ever with the shroud.  The inherent problem with such a design would be that the baffles would have to have a large enough hole so that you don’t get baffle strikes.  That would make the thing a bit louder. 

There is the slight change in velocity that one may encounter with the moderator as well, but for reasonable ranges, the velocity variations may be greater than any increase or decrease in the average.