O-Rings on FX Liners

I'll be interested to hear the answer to this as well. I noticed that my STX barrel came with a pellet liner, which had 3 o-rings. I also ordered the slug liner, which came with 2 o-rings. I couldn't find anything definitive about how many there should be, or if they were really even needed. I can't imagine their placement is all that critical since it's pretty much impossible to know where they end up once you slide the liner in place. I've thought about putting 2-3 layers of heat shrink tubing on the liner at the point where the o-rings go, then hoping that helps keep them from sliding on the liner. 

Cheers,

Rusty

I know the 'barrel' in a system like this needs to accommodate a .177 liner as well as a .30 liner, But I wish the OD of the liners made up the gap rather than having to use orings as 'spacers' I also understand than what I'm thinking would make it tough/impossible to imprint the twist along the length of the barrel. Maybe a Delrin sleeve? (same concept Rusty brings up) but whole length?? I don't know if it really even matters as I think the liner is tensioned. 

I'm interested in a 'B' liner for my impact but I don't want to frustrate myself more until I finish a few other projects....

And more specifically to the OP... If you trust the outer barrel to be straighter than the thin liner, especially under momentary pressure, than bracing the liner (the orings) will prob be a positive, at least to some extent.

Blue painters tape, split down the middle, then wrapped around the liner 3 or 4 times, one either side of each oring that you would like to place works a treat. The same concept as a Delrin sleeve on either side of the oring only using a thin sliver of tape to build a groove.

I read this somewhere and credit needs to go to someone else for this simple and easy solution, I have tried it and am very happy that I can be certain the oring doesn't move from where I place it.

I don't know that it improves accuracy, to be honest, I actually put an extra one in there, on my impact I have one oring placed at each barrel support and then one towards the muzzle and breech.

It's also easier to get excited about the .22 cal slugs when you see the BCs that NSA publishes for them. I'm not sure why they don't publish number for the other calibers, and we can only guess whether they're better or worse. The higher BC slugs for .22 are already too long for the magazine, and I fear the larger calibers would be too long to even single load if they try to make the BC as high as possible. It will probably be a while before we really know what works best. 

As for the o-rings, I know I saw some speculation in videos about whether they were needed, but I don't recall seeing any actual test results, or comments about testing without them.

Rusty

Is the .177 barrel thinner so you need fatter o rings?

I have tried everything adding o rings, removing o rings, making Delrin spacers. didn't seem to make any difference. For me what made a noticeable difference was barrel tension. I found that a preload of 20-25 inch pounds works best for my Impact. This is where I got the tightest groups. One other thing after you get your gun zeroed and dialed in you need to mark your barrel liner tdc so you can put it back in the same place. 

That's what I love about AGN every one shares info and questions and we all learn about the guns and sport and we don't have people humiliating others because they don't agree with something someone said. Great site keep up the good work AGN.

Thanks for the info. I had wondered how tight that liner needed to be, and the only thing I ever saw was to just snug it, not really tight. Just what I need, more variables

Rusty

Pulling up this old thread to ask a question or two to the experts.

I just got slug liners and went to install it. When I pulled out the pellet liner there were three o-rings on the liner, spaced not quite evenly, dividing the barrel into quarters.

I put the o-rings on the slug liner and pushed it in but when I tightened it up it didn't bottom solidly...it had a weird squish. I looked inside and noticed there was an o-ring pressed behind the slug liner. Did my pellet liner have 4 o-rings and one came off? Is it supposed to be there? Is it supposed to be located over that small indent near the breech end of the liner? I'm confused at what locates the liner at the breech end if there were no o-rings. It is hard to see if there is some kind of shoulder there or not.

I don't have pictures but one oring is secured at breach end in the shiny steel cylinder (liner attachment) in between the brass transfer port and the barrel tube housing, I don't think that oring can fall out the tube only way top remove to separate from the barrel tube.

The liner came with 3 orings but onse you pull it out the orings not in place anymore. Do you know what is a tube node point? Never mind....take the entire length of the liner and divide by 3 (this is roughly about there, but can be calculated if you really wish). Place one oring on each end 1/3 from the end and place maybe 2-3 in a sandwich in the middle.

How many orings you need? 3 at least to locate in space, but you may find it in future to play with softer or stiffer rubber material, mostly depend what weather/climate conditions at your place.

Use your common sense how to locate them there, you can use let say electrical tape or plumbing teflon tape or painters edging paper tape and lock the oring from both sides. When you push in the liner you are all set, most likely you won't miss any more precise mathematics. This way you have a floating liner inside the barrel tube.

FYI with archery arrows the node point is more important because that tube actually flyies, the airgun barrel tube is only a "pointer+leader" until the projectile leaves the muzzle.

I personally use vinyl electrical tape building up small tape walls on each side where I want the oring to stay. After building the first wall I slip the oring on the liner. Continue with your tape crossing over the oring with one rap of tape over and around the liner, to start build the table wall on the other side of the oring. Never cutting the tape from one wall to the next. Take care not build the walls taller then the o-ring. To install I coat the tape with Ballistol and slip it in. I started doing it this way becouse I found some times the oring even with tape wall it would still roll up and over the walls .Cheers

Thanks for the tips. I used painter's tape. Something strange is going on however because now I'm having poi shifts I never experienced before. Shooting 33.5 gr. NSA's which rock over and jam in the side shot magazine. So I started tipping the gun down and shaking it and started getting poi shifts. Never had that with the pellet liner even when lifting it by the shroud.

I switched to single loading for now but that required a lot of tipping the gun down to drop in the slug and more poi shifts.

Going to take it apart tomorrow and try again.

Is this the first time trying slugs with this particular liner? If so, it just may be you haven't found the right slug or tune. Slugs act goofy that way. 2 in one spot, flier and three in another. They dont act like pellets. Try shooting a few pellets from the liner to confirm.

How many mm barrel? My 700 had 4 orings. The bottom one always seems to come off the liner and you need to tip it over so it will fall out the sleeve. Never dry fire to shoot it out.

The FX website has clear diagrams for the different calibres and the number of factory fitted o rings. Check the Tables for your specific calibre

Aha. It is a 700mm barrel. Thanks.

First time shooting it. I will try pellets too.

Was shooting 33.5 gr. .250 NSA's at 850 fps or so. Would get a tight group of 3 and then the next one would be a half inch to the left.

I think I got it sorted. Thank you for all the help.

I tore it back apart and installed all 4 o-rings spread apart evenly. The o-rings had slid over the painters tape I used before. I replaced that with electrical tape. I mic'd the tape wrap thickness to be just below the I.D. of the shroud (.455 ".) I left space between the two tape walls for the o-ring to expand.

During the disassembly I noticed I got confused on the orientation of the liner and now I'm thinking I might have initially installed it backwards. That certainly would account for accuracy issues!

Shot slugs of different weights and didn't see any POI shifts.

Now I'm sorting a different issue which I'll post separately.

Anyone knows if more o-rings than originally placed by FX has any posotiv influence on accuracy?

for example the 500 mm liner has 2 o-rings in factory delivered gun. Would it make sense to put 4 or 6 o-rings at the outside of the liner ? ( or pair them )

cheers 

What works like a champ, for any number of orings that you decide to use. Make sure they are the correct size from the FX drawings online. Then place the orings where you want on the liner. Take about an inch to inch and a half of the thin white Teflon tape and wrap it tightly (stretching it as you apply) to the oring. This will keep the oring in place when you insert it in the barrel sleeve. Justin Welch told me about this last year when we were shooting together at the CA State FT at Morro Bay. It works, give it a try!

Mike

Thanks Mike Good tip with the teflon. Does the amount of rings make a difference ? If so what difference ?