Smoothing out the action?

:hoot:

Are we trying to pinpoint, and fix, a non-existent problem?

My Vulcan shoots like a laser. I’m not aware of any appreciable number of reports of other Vulcan owners having accuracy problems. Considering that 99.5% of accuracy problems are the shooter, and not the gun, where are we headed here?

Granted, the original poster may indeed have a mechanical problem, but has anyone else experienced this with any degree of certainty that a probe is involved?

Hoot:

:hoot:

Mine has shown no such problems.

Hoot:

Yes, the image is at a slight angle and doesn’t show the entire pellet skirt, but I did intentionally photograph at an angle showing the entire interior flat of the pellet. The pellet probe mark is indeed off center, not an illusion.

I didn’t select a special pellet, it was simply the first Air Arms pellet in the magazine. Thin, soft skirts for sure on the AA, but they group nicely.

:hoot:

The amazing thing, to me at least, is how accurate pellets remain, given that they are spinning tens of thousands of times along their axis in the brief travel time they have in their trajectory. Even the most minute of flaws, indentations, bent skirts, or gouges will have an effect magnified many times over, due to the gyroscopic action of this rapid spin rate. In one super slo-mo video, I watched a pellet actually fly in circles around it’s forward trajectory…a “corkscrew” flight, from barrel to target. I didn’t think that was even possible until I watched it happen.

Hoot:

The alignment of the pellet in the barrel would best be accomplished by the pellet skirt. Too thin of a skirt may partially collapse and not serve this purpose. The probe can’t fill the skirt area as that is where the high pressure air begins to push the pellet. Perhaps the place the probe contacts should be an indented cone shape to facilitate centering the probe. Then too if the probe were bent off center or doesn’t have adequate centering movement maybe it could throw off the gyroscopic stabilization.

guykuo,
Try not fully seating the pellet, take a picture of the probe mark, then lightly work the probe back and forth possibly putting additional marks on the pellet. Then another picture please, to show if there is any variation ❓
Other brands such as Baracudas may have a thicker skirt and show a different result.
We don’t have an accuracy problem with JSBs so maybe we’re only concerned with prevention of an occasional flyer that only messes with our one-holer groups at 100 yards.

As I see it, the pellet and pellet probe being eccentric to the barrel could position the pellet pointed off axis i the chambered barrel. With the pellet probe using off center, how on earth is it getting the pellet’s axis aligned with the barrel? If it is off axis the gyro action won’t be in precise alignment with the aerodynamic envelope —> spiral more (as Hoot expounded).

More on thread topic, the off center push and deviated pellet would be a bit harder to push into position.
The occasional, harder to seat event does happen with my Vulcan. I’m pretty certain it’s not the gun’s own parts suddenly being difficult to push forward. It’s a pellet that is entering the barrel in a not quite orientation and being harder to push forward. That or the pellet is misshapen.

If it were practical, we would precisely align the pellet probe, pellet center, magazine opening and barrel to all be on the same axis. It’s clearly not and I’m pondering what is practical to do.
This is probably why single shot adapters have the potential for higher accuracy — you can better control the pellet alignment during seating.

:hoot:

Rotation of the pellet depends on the “rate of twist” of rifling in the barrel. The weight and length of the projectile all determine the necessary twist rate for accuracy.

Too little twist and the projectile is unstable, tumbles, keyholes, does all manner of things bad for accuracy. Recall the smooth bore muskets, whose projectiles would undulate up and down, and even sideways, in their trajectory in flight. Rifling the barrel stabilized the projectile in flight, but the rate of rifling, per inch of barrel, had to be carefully calculated.

Too much twist and the pellet begins to manifest some strange ballistic characteristics. No projectile is perfectly round, or perfectly balanced, and at extremely high rotation rates the projectile can even take a circular trajectory towards it’s target…which is to say the projectile path is not straight, but will travel in a path that resembles a “coil” in shape, think of a slinky stretched from point A to point B, with the projectile traveling a path identical to the coils in the Slinky,

Rifling creates a stabilizing, or gyroscopic effect. However, if the projectile is out of round, has a nick, bend, microscopic protrusion, or other defect, the laws of physics demand the gyroscopic rotation accommodate the effect of the anomaly in it’s rotation, and this results in strange, almost non-ballistic effects on the projectile’s path.

Some of the new .30 caliber pcp’s have experienced a “corkscrew” trajectory…which creates seemingly unexplained impacts on accuracy. One place seldom explored is whether the rate of rifling is suitable for the projectile length, weight, and shape. Hence…some pellets are more accurate in a specific pcp, than another pellet of a different configuration.

These are my thoughts on the matter. Right, wrong, whatever, physics always plays a critical part with accuracy/consistency in travel through space/time.

Hoot: