FX Crown liner : 2 or 3 Orings , does it matter?

[aldea6]

Hello

When I removed the .22 liner from my FX Crown to put a slug liner , I found only 2 Orings on the liner . My groups with the slug liner were not very satisfying . I decided to go back to the normal liner , put the 2 Orings , ....and the result was not good at all. With JSB jumbo heavy , pellets go left , right , low , high....I don't understand the cause. I wonder if I could have lost an Oring when I removed the liner.

So my question : is it important to put 3 Orings on the liner , and is their position critical to the accuracy of the gun?

Thanks

Aldea6

 

[Tkristbaum]

What barrel length? It might matter for the longer ones. My wildcat only has 2.

 

[Wilber]

My 600 mm .25 Pellet liner had 2 "O" rings. 

 

[Revoman]

The 700mm 'lite' Continuum has 3 'O'-Rings.

mike

 

[aldea6]

My Fx Crown in .22 has a 500mm barrel , so it's maybe not very important . However I noticed that the shroud moved side to side by only a few degrees , the barrel beeing thighted by the grub screw , and not moving.

 

[tor47]

To have the shroud in same position, you should rotate and lock it in place every time.

 

[SteveG]

From FX USA:

Good morning Steve - 

There should only be 2 orings. They will shift, that is normal. We don't recommend taping them in place. Just arrange them so they are spread out over the length of the shroud and you should be fine. Crown MKII is an incredible rifle....ENJOY! You should have a superlight barrel.

Thank you and have a good day.

Best Regards,

Melissa

 

[SteveG]

All,

To the last reply from FX USA some additional context. I have a new FX Crown MKII with a 600mm barrel. When I removed the shroud and cleaned the barrel, I could see the o-rings had moved and this can affect POI. Many people use tape to hold them in place and I plan to position them with a push rod and have one close to the muzzle and the other midway from the center of barrel liner to the breach or pressure nut holding the barrel. I discussed with Utah Airguns as well and they've reported mixed results adding additional o-rings etc. so we'll have to experiment with placement and numbers.

Good luck and all the best!

Steve

 

[bigHUN]

Put the orings inside in between "node points" about 75% away from node point.

Every tube and rod in any material, really doesn't matter round or square - has node points.

google for "node points on tube" to get a picture what that means for oscillations = harmonics.

 

[Goldwing]

Put the orings inside in between "node points" about 75% away from node point.

Every tube and rod in any material, really doesn't matter round or square - has node points.

google for "node points on tube" to get a picture what that means for oscillations = harmonics.

Could you explain this "node points on tube" ?

Thanks

 

[bigHUN]

Could you explain this "node points on tube" ?

Just a short one:

#1 Every "free standing/floating" tube/rod/broomstick has two node points. When you hit the "tube" it makes sound = oscillates but not the node point = static.

#2 Every tube/rod/broomstick has one stiffer side and one weaker side (or more, depend of a manufacturing process precision of design intent).

#3 The oscillation if not controlled - will always be in the plane of a weaker side. Remember why we do indexing the liners/barrels.

Take a look the right side picture. To "dampen" the oscillation, for a best result place the orings equally spaced in L/2. (the left end of the liner is nested in a port piece the right end of the liner is nested in a muzzle nut piece, but no one is welded in for a rigid connection, if yes, that would be the left picture).

#4 You cannot and shall not zero the oscillation, it must come out somewhere. Everything in our world resonates with any kind of frequencies.

Edit:

You can even find a node point on the tube easily. Take the liner, hold it between two fingers tight enough not to fall out but not to be a rigid connection.

Let it swing between two fingers.

Now knock it gently at the middle of length to edge of a wooden table, do you feel it resonates? now knock it again little lower/higher, again more higher...when the resonate stops and don't feel it any longer = there is the node point...keep going towards the end and you start feeling it again. How you coming closer to a node point the sound is changing to a higher pitch, coming closer to the middle in between two node points the sound is changing to lower pitch = frequency.

You can ever mark it with a marker, bot node points, what you feel the resonate is very close ballpark if you would calculate. Also a very rough estimation is shown in the upper right picture.

 

[Goldwing]

Holy crap! as Frank Barone would say geart explanation !

 

[SteveG]

bigHun,

Thank you very much for the explanation on nodes points, very interesting indeed. Now master, before I snatch the pebbles from your hand , what if the barrel of my FX Crown MKII does not touch anything at the muzzle end (see picture). From what I can tell the end of the barrel does not contact the internal baffles at the muzzle, just the o-ring. How would this affect the nodes oscillation? 

 

[Corvid_hunter]

The one closest to the muzzle should be 1.2" from the end. I taped mine to stay in place.

 

[SteveG]

From the end of the barrel?

 

[SteveG]

bigHUN,

I assume adding more than 2 o-rings would not make any difference based on the node points and why FX only placed 2 on the 600 mm barrel. They install 3 on the 700 mm barrel. Thoughts on more o-rings and harmonics?

 

[Corvid_hunter]

From the end of the barrel?

1:04:00 on this video explains it.

https://www.youtube.com/watch?v=Dzs_muWHE5s&t=4367s

 

[qball]

@bighun: that’s why I glue a carbon liner sleeve on and then place only 1 spacer at the very end of the barrel so it behaves like a free floating barrel with only 2 node points. Best would be no touching the shroud at all but FX barrel and shroud attachment are weak for that. 

 

[bigHUN]

@bighun: that’s why I glue a carbon liner sleeve on and then place only 1 spacer at the very end of the barrel so it behaves like a free floating barrel with only 2 node points. Best would be no touching the shroud at all but FX barrel and shroud attachment are weak for that.

I did not glue...I wrap a Teflon tape on the sleeve not to overlap

Also the best would be to stretch out the liner (as a guitar string) and not compress it, but that change must come from the design I don't think we could make it DIY.

 

[qball]

I did not glue...I wrap a Teflon tape on the sleeve not to overlap

Also the best would be to stretch out the liner (as a guitar string) and not compress it, but that change must come from the design I don't think we could make it DIY.

I also don’t see a way to stretch the liner, more work than it’s worth regardless. Having the sleeve glued/epoxied on is a personal preference, I prefer epoxy because I know it will not move twist or change at all from vibration, indexing or reinstalling/switch liners or any other reason. This is to make the barrel as solid as possible and remove any possible variables. Some might ask why remove variables? Because when I find this at 100 yards I don’t want it to change at all!

having just one spacer at very end helps preserve free floating like harmonic node and I had great results from it on multiple barrels. YMMV!