Tuning SPIRALING PELLETS

[Xbowsniper]

Nation, 

First, you need to take in account a couple of things.

Fist, you say it "spirals". Which way does it do this? Clockwise, or counterclockwise? This makes a BIG difference. 

Almost all airgun barrels, regardless of what caliber or brand, is a right hand twist. Meaning, as the pellet moves from the shooter to the target, it is spinning clockwise. If the spiral is that is causing this action is clockwise, it is usually one of these issues.

It is either poor quality pellets, damaged barrel, including poor crown, clipping of the moderator or LDC, fouled barrel that needs extensive cleaning, or a combination of any of the above.

If the pellet spins clockwise, but the spiral is counterclockwise, the opposite direction of the spin of the pellet, it is almost a given that the pellet is being pushed at a velocity that it doesn't like. Just because it does it at a low and high velocity, doesn't mean that it will happen at all velocities. It also is usually due to a poor tune as far as harmonics are concerned. I've seen many times where a well tuned barrel is shooting lights out, then a moderator is installed, and its all over the place. And vice versa.

In order to diagnose the problem, to need to remove the barrel from the gun. Now you can use bore cleaners of your choice, being that there's no o rings or seals to damage.

Reinstall the barrel. Shoot at the highest velocity that you shoot. Lower the velocity by 10 FPS until the spiral goes away. Just because it spirals at a low velocity and a high velocity, doesn't mean that it will spiral at all velocities in between.

I had a guy at my home range that had the same thing happen. He reduced the velocity by 10 FPS, until it went away. I'll post the video below of what the pellet was doing when it was spiraling counterclockwise, while the spin of the pellet was clockwise. The video below is a prime example of an improper velocity/harmonics issue.

https://youtu.be/C7c9Noa4v4g





Tom Holland 

Field Target Tech 

Fieldtargettech.com 

 

[nervoustrig]

Tom, thanks for sharing that. I haven’t run into CCW spiraling but it’s good to know where to turn my attention when it happens.

 

[trlrman]

you guys are more seasoned on this than I but....pic 3 & 6 look like damage to the head and skirt ?

 

[nervoustrig]

In the next to the last picture, right where the pellet skirt is resting against the fabric, there appears to be material missing from the skirt. That looks really concerning.

Then to a lesser extent, in the first 2 or 3 pictures, I’m not real excited about the little fins extruded behind the head where it met the rifling. Those can behave as little rudders. However it’s hard to imagine a scenario where those would have been suddenly introduced today. That’s usually more of a product of the rifling geometry and the pellet’s alloy and fit. So for example, if you recently switched to a new tin of pellets from a different manufacturing batch, that could be a reason. Otherwise I would just recommend confirming that this artifact is reasonably consistent all around the pellet’s perimeter, meaning you see the same little fin behind the spot where each land engraved the head. If not, they can help set up a spiral.

 

[Xbowsniper]

Nation 

If you look at the pellet pictures above, the statements by nervoustrig are correct. This tells me that the pellet head diameter might be too large, to have this type of deformation. Also, by looking at the sides of the pellet, they kinda look a little bit rough to me. I'd like to see a picture of the pellet not from the side, but from the rear. I'd also like to see a picture of the dome of the pellet. This would give a more rounded picture of what's going on with the pellet.

Tom Holland 

Field Target Tech 

Fieldtargettech.com 

 

[2D1C]

This last one hasn't been loaded. right out of a tin

 

[trlrman]

Maybe probe pushing in at a angle ? (Bad seating ) ?

 

[Xbowsniper]

2D1C,

I would maybe try a different batch of pellets. To me, those heads have too many imperfections in them. What weight and brand pellets are these?

This is the reason H&N discontinued the Sniper Mediums along with some others. The heads were not coming out smooth, and had tiny imperfections in them, and their performance, or lack thereof, proved that. Couple that with a possibility too tight of a pellet/barrel relationship, along with too fast/slow of a velocity, and that could be your problem. It might be as simple as trying a different tin/lot of the same pellet.



Tom Holland 

Field Target Tech 

Fieldtargettech.com 

 

[2D1C]

Thank you Tom, I will do that it was a newly cleaned and lubed tin. It would be expensive if that's it! @trlrman I did get a 1/4 on the probe.

 

[Jlacouturec]

check the shroud/suppressor baffles, maybe on that double load it clipped some baffles, test it without shrouds!

 

[2D1C]

Been there done that. I am going to try different pellets and put my 600mm barrel off my Crown and see what happens there

 

[Enkey]

If you exchange the barrels, you will rule out that this is the problem

 

[nervoustrig]

...it was a newly cleaned and lubed tin.

From the same manufacturing lot as the pellets you had been using just prior?

Otherwise the new tin might be fat heads. That would explain the fins extruding / smearing where it meets the rifling.

 

[2D1C]

I don't remember if I changed tins or not. I am going to try different ammo and a barrel swap. This should be interesting!

 

[Xbowsniper]

Enkey is right. Leave the barrel, change ammo. If still spiraling, adjust to lower velocity. Change one thing at a time, or you'll never find the problem. Pellets first,change velocity....If that doesn't work, then change barrels. Were these always spiraling out of this barrel, or did it start happening after they were flying good?

 

[2D1C]

I am narrowing it down some. I took the 600mm of the crown and mounted it. It shot GREAT! with 2 different pellets and two different slugs. So now it is either the TP, ammo or the barrel.

 

[bandg]

Certainly interesting. Ammo? Seems unlikely if you shot the same pellets after the double load and it started exactly at that point. Something (lead fragment?) jammed at the TP or TP/barrel junction? Probe or barrel damage? Wayward gremlin took up temporary residence?

 

[2D1C]

I couldn't get out to 100 with the 600mm but @ 60 it was great. The range opened so I put the 700mm back on and it still spirals. I will go to the range Sunday and see for sure how the 600mm does.

 

[Xbowsniper]

2D1C,

Did these pellets always spiral, or did they fly good once, but not now? If they did fly good, but not now, swapping barrels isn't going to find the problem. Leave the problem barrel on, systematically check everything that can be checked. Clean the barrel.......again. if the patch doesn't come out spotless, keep doing it until it is. Use a nylon or soft brass brush if you must. If it was spiraling all along, no matter what the velocity, maybe it's a potty barrel. Happens. If it was shooting well, and all of a sudden it spirals, there HAS to be a reason. As stated above, maybe a transfer port/thimble/alignment issue. Maybe a chunk of lead from the double load is stuck or lodged in there, as was suggested above. Has to be a reason for it, and it can be corrected!!!

Tom Holland 

Field Target Tech 

Fieldtargettech.com 

 

[2D1C]

Well gents I tried different ammo, velocities, I scrubbed the barrel with a brass brush then patches until white. Tom It was fine until the double load. I didn't run bore paste as I don't have any. That said I took the 600mm out, running 895-910 . WOW!! I expect these guns to shoot MOA in the decent conditions. But that day? I had two 5 shot groups at sub .75 So I am not pursing this any longer and will ship the liner to Augie if he wants it or one of you if not.

I really appreciate all of you sharing your knowledge with me and others.



Regards,

Dennis