N/A Barrel harmonics or ideal pellet speed.

[Berserkeley Mike]

I like to try to understand why things are the way they are, like, why do I miss so much? I can understand that if a barrel points in slightly different directions as it harmonically wobbles about, then I'll miss a little less if I can time the pellet to leave around when the barrel is changing direction. The barrel will point for a longer time in the same direction while it decellerates, stops and accelerates again, whereas mid-swing the barrel is changing direction rapidly. And I kinda understand that timing both the pellet exit and the harmonics in general depends a lot on pellet speed (and thus weight and power setting).

But how about pellet stability and spiraling?

Ted's Holdover has a video where he shoots the same gun at 1100 vs. 800 fps, and sees spiraling at the higher speed:

There is another where he sees spiraling when the barrel is dirty:

I thought of these when I shot some otherwise accurate pellets out of an otherwise accurate barrel, and watched them spiral a foot or more at 50m (I think in my case they were going too slowly).
Maybe speed and dirty barrels are related, maybe not.
But anyway, is that harmonics with the barrel? Or something about the pellet and its airspeed, independent of the barrel?

- Mike

 

[JimD]

The pellet going unstable and spiraling is not the harmonics of the gun, it is the spin rate of the pellet which is closely related to the pellet speed but not exactly the same thing. The twist rate of the barrel plus the velocity of the shot determines the spin rate. Spin it too fast, especially if it is windy, and the pellet may not be stable. In light wind, low to even mid 900 fps may shoot great. But when it gets windy, the pellet may become unstable. I tune to stay under 900 fps most of the time because I want the pellet to stay stable even when the wind is blowing. My target for my current "new gun" is 875. My most recent string averaged 880 fps so it may stay there - needs a bit more testing.