Tuning FX Superior liners - uneven crown

[Seeker]

Howdy!

Please just take a look. This is the same liner rotated by about 180*:





How can they shoot pretty straight? Pretty much every liner which I examined has that problem.

 

[nervoustrig]

I would fix it for the peace of mind but my experience has been that a slightly irregular crown has far less influence than, say, a micro burr left behind from the crowning operation. By "less influence" I mean usually indistinguishable amidst all the other variables that contribute to dispersion at a distance.

 

[DennisB]

Crown

If its not right Send it back to the seller/mfg.

You paid good money and got a not perfect product.

DennisB

 

[Seeker]

I would fix it for the peace of mind but my experience has been that a slightly irregular crown has far less influence than, say, a micro burr left behind from the crowning operation. By "less influence" I mean usually indistinguishable amidst all the other variables that contribute to dispersion at a distance.

Do you think a brass screw method can help here or a lathe is needed?

Crown

If its not right Send it back to the seller/mfg.

You paid good money and got a not perfect product.

DennisB

As I mentioned - every liner which I checked has that problem to some extent and I checked about six of them.

 

[nervoustrig]

Do you think a brass screw method can help here or a lathe is needed?

If you start with a facing cut, yes. I don't recommend simply going at an uneven bevel and trying to make it uniform but I suppose you could sneak up on it with very careful attention to detail.

 

[qball]

The crown is how Fx makes them. The internal diameter or the thickness of the wall of the barrel/liner has slight variation due to the rifling process. the rifling is pressed in or caused by deformation of the perfectly round tube so the tube isn’t round anymore so you can not get perfectly even crown no matter how you try. This is not a traditional barrel. 


Just shoot it and see if it’s accurate, all my liners crown look like that. If you try to “fix” it you might ruin a perfectly good shooting barrel/liner. 

 

[nervoustrig]

Um, an out-of-round barrel would not be good. Wall thickness can vary but the bore must be round, and therefore should develop a uniform bevel when crowning.

 

[dc8cappie]

If the bore is slightly off center this is how the crowning will look if done on a lathe. OMO

 

[Centercut]

Agree with @dc8cappie. Yes, it appears the ID and OD are not exactly concentric... but it does appear that the crown where the pellet actually leaves the barrel is fine, and its a pretty good crown job.

 

[nervoustrig]

Mark, what is the wall thickness across at those two 180deg positions?

 

[Seeker]

I don't have a proper tool to measure it. Caliper does not seem to be good enough. However, if one aligned the bore, not OD in a lathe then it would not look like that.

 

[bigHUN]

... micro burr left behind from the crowning operation ...

I did a crowning over the weekend on four of Leshiy2 barrels and once I was there I just re-did on FX liner as well this one without re-facing.

On .22 looks/feels better but the .25's when I push a pellet through I can feel that "wire edge" you describing. I tried many things and just could not get rid of it. {maybe a very first abrasive could be too rough? I did not tried to start with the next grit...)

Maybe shooting 50 pellets through can clean that micro burr and I just revisit with a very slight touch?

The Hunter friends may not be bothered with it, but I would like to shoot and score rings and having it in my mind really pokes.

 

[Vetmx]

Know you know why we have to index our liners. 

 

[bigHUN]

.......index our liners.

I rolled the Superior Heavy first time this weekend - on four bearings (my arrow cutting jig) .......... it was an eye opening. Next time I buy a liner I am taking my jig to the store and test it right there with a dealer (2-3 hrs away btw but I don't care how far).

This liner I was indexing back couple months ago, the 10 shot/each - pattern center was about 4-5" radius @ 100. To the left of my scope optical center.

 

[Seeker]

I wonder how many straight liners you will be able to find. Could you share your tool?

 

[bigHUN]

Arrow spine indexing jig. The shaft sits on two ends and in the center put a weight. Rotate the shaft and it will show the stiff and weak side of the tube.

Two bearings on one end and same at the other end

Make it you can adjust the length

I don't have a lathe, but I needed something to face-polish the barrel

And just out of curiosity I put a FX liner and started rotating.

 

[bigHUN]

Now I just remembered seeing a YT video a while back when E.R. was straightening the FX liners. I don't have a courage to do it on my only one liner which is working so-so, no spares but I would try next time.

 

[Seeker]

Ernest was straightening liner housings actually.

What was your discovery with liners?

 

[bigHUN]

What was your discovery with liners?

I placed the bearings on multiple locations and just rolled the liner. let say you put a bearing on left end and one in the middle and roll it, visible by eye the right end was playing = not perfect straight.

 

[nervoustrig]

I don't have a lathe, but I needed something to face-polish the barrel

Doing it to make the muzzle pretty, right?