Pellet Twirling problem
Hello guys,
I’ve noticed that the pellet is twirling through my scope.
I’m using jsb 18.1 grains at 890ft/s.
I tried to slow down the muzzle velocity but nothing changed.
Any suggestion please?
Wish you all a merry Christmas
All Replies
Yes. Take it to your dealer and show him!
Hoot:
I screwed the cocking rod completely tight. I just tried to cock and it worked. I hope i didn’t do any harm… Thank you gukyo for your help 🙂
Anyway this gun is amazingly easy to tune and repair…
So you rotated the cocking rod guide completely off. Hopefully you screwed it back on to about the same position. Otherwise, you will have changed the fore/aft positioning of the cocking mechanism. Too forward (longer) and the gun will give great resistance against latching the cocking knob in the open position. Too backward (shorter) and the gun won’t reliable cock the hammer.
The pellet probe body is under the rear top cover of the breach block. It is the large diameter brass cylinder into which the pellet probe screws in. The cocking rod attaches to the probe body via two screws and a spacer. Sometimes, you can change the alignment by loosening those two screws, holding the alignment as desired and then tightening the screws. It won’t let yo do a big shift, but you can affect things a bit.
Like I said, if you aren’t feeling any resistance as the pellet probe’s wide portion initially enters the barrel, a slight misalignment is ok. It is normal to feel some resistance a few mm in when the probe meets the o-ring. Silicone greasing the o-ring can reduce that (normal) resistance.
I tried rotating the cocking rod but the pellet probe didn’t change its position. I rotated it all the way off course after taking off the knob. Is it bad that the pellet probe isn’t centered to the barrel hole?
No. Not tighten anything in this picture. The part you tighten is the brass pellet probe. That gets screwed into the probe body firmly. If the alignment is off center, it could be bent or the probe body was not aligned when the cocking rod was bolted onto the probe body. There is some play in the barrel for the probe body. So, the probe can be off center a little bit and still center itself as enters the barrel. If the probe extends into the barrel without any palpable resistance until it meets the o-ring you are ok.
Replacing the o-ring is easier if you first advance a cleaning pellet. That helps keep the o-ring from falling forward too far. With that and a dental pick (dulled of course) you can change the o-ring without removing the barrel.
The cocking rod guide, in the image you posted above, is the piece that the cocking knob screws into. Notice how that it has holes every 90 degrees. You can rotate the rod to bring a different hole into use for the cocking knob. Doing so changes the fore/aft position of the cocking rod and pellet probe. The positioning has to be checked with the slotted plate in place. The slotted plate determines the movement limits of the knob. If you check without the plate, you may find things don’t work properly once the plate is back in place.
Don’t mess with actual cocking rod and its connections unless you understand how it all works.
Is this the part u mean i should tighten gukyo?
I noticed that the probe is not aligned well with the center of the barrel when it’s firmly tightened. I unscrewed the probe a little bit and it’s aligned. Is this ok or I’m doing it wrong?
I read what gukyo said but i didn’t really understand what to do
Thanks guys for your concern. I’m new to vulcan but not new to pcp. I already worked on my hw100 and now it by heart.
I inserted a a fishing wire in the barrel and when it’s at the other end i pull a small piece of cotton tissue. That’s how the guy at the shop taught me to do.
I just changed the oring and shot one shot, it seems i solved the issue. I had to take off the barrel in order to insert the oring, i hope i inserted it as it should be placed. With a torch lamp i made sure to align the hole of the barrel with the hole above it when removing the screw.
The merchant also told me not to change the muzzle velocity and keep it as it was from factory because vulcan is perfect the way it is. I don’t know if i should believe him.
The probe seems to be aligned as it should be.
Tomorrow will do more tests.
Regarding the scope issue and the spiraling i see i believe i need to read more about scopes because I understand very little about it.
Thanks
Gelie68,
If you’ve already done what was advised by the guys here (e.g. cleaning the barrel, shooting without the shroud, adjusting pellet probe, etc.) and are still experiencing the problem, here’s something to think about: at what distance was your scope focused at when you saw the pellets spiral? Keep in mind that parallax will manifest itself at distances that the parallax setting on your scope is not set to. So, during the shot cycle and when the rifle moves due to recoil, your scope is obviously going to deviate from its original position in relation to your head/eye position. When this occurs, you’re going to get the illusion of the pellet moving erratically even though it is not; it’s because the effect of parallax, combined with the movement of the reticle (from recoil), exhibits a wobbly flight path of the pellet once it passes over the focus distance.
:hoot:
Tear a tissue into strips. place one over the suspect points. When you shoot, IF you on the source of leak, the tissue will fly off. This will help locate the source. Check the breech carefully and try to identify points of possible leaks then isolate the problem.
I can’t guarantee this will always work, but it has in the past. Usually the breech/probe area is the culprit, and the O ring is the part.
Hoot:
I’m a bit hesitant to suggest making gun adjustments, because your degree of experience working on airguns is puzzling. Asking about o-ring and cleaning the barrel right after the shop cleaned the barrel leaves me a bit concerned. Are you new to airguns or just new to the Vulcan? Do we need to step back and check how you are cleaning the barrel?
It is possible that tightening the probe shortened its length sufficiently that it is no longer going far enough into the barrel. If the probe does not go far enough forward to seal against the o-ring, you will get a puff of air. You don’t adjust the probe length or position by loosening / tightening the pellet probe. It simply needs to be tight, never loose
You can adjust the fore/aft position of the pellet probe by removing the cocking knob and rotating the cocking rod guide to another hole position. Rotating that guide to another hole changes the effective length of the cocking rod. Don’t go merrily spinning the rod guide. Just 1/4, 1/2, or 3/4 of a turn should be enough. Adjust so the backwards travel is just a bit more than needed to reliably cock the hammer. That should also set the position for proper forward position. BTW, this adjustment may also be needed if one switches to the biathlon cocking lever.
You’ll also get a puff of air if the screw atop the breach block isn’t sealed with a bit of teflon tape, but that probably isn’t what is going on.
Yes, new O-ring. Also make sure when you tightened the probe it is aligned. Just move the cocking Bolt back and forth while watching the probe to make sure it goes straight and true. Good luck!
Guys i was cleaning my barrel and the o-ring came out. I placed it without problems in its place. Also i noticed that the probe that pushes the pellet in the barrel was loosened so I screwed it clockwise and tight. Now when i shoot i have air that shoots in my eye. Could it be because I should put a new oring or because i tightened the probe?
I took it to the shop. He did a deep barrel cleaning with wd 40 and then with ballistol. The barrel is very clean now. Tomorrow will try shooting.
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Pellet spiral is inherent with the diabolo design… I think.