Tensioned or Free Floating?

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Has anyone ever made an aftermarket barrel for the FX (taken a LW or similar and machined it) to the same dimensions as the liner on the current barrels and tested it? It would be significantly heavier, but stiffer.
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But how the barrel is secured into the receiver still sucks. The greatest barrel in the world held into the receiver with orings and grub screws is only going to live up to half of its potential. The airgun world only needs to take one thing from the PB world, thread that barrel into the receiver. 
 
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Has anyone ever made an aftermarket barrel for the FX (taken a LW or similar and machined it) to the same dimensions as the liner on the current barrels and tested it? It would be significantly heavier, but stiffer.
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But how the barrel is secured into the receiver still sucks. The greatest barrel in the world held into the receiver with orings and grub screws is only going to live up to half of its potential. The airgun world only needs to take one thing from the PB world, thread that barrel into the receiver.
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Completely agree! I have a TJ barrel fitted to FX and accuracy is not Really different and it’s a lot heavier. There got to be a way to make it better.
 
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Here is what I did, and what my impressions are.



I used the CF liner sleeves and tensioning tubes on 2 Impacts, a .22 X model upgraded to latest MKII spec. and a MKII .30 cal.

I used JB weld to bond both the liner sleeves and the tensioning tubes in place. The tensioning tubes were LIGHTLY tensioned while the JB weld set up. The reason for bonding the tensioning tubes in place was that I wanted to avoid any differences in thermal expansion creating potential problems down the road, so I homogenized the assembly. They were LIGHTLY tensioned to avoid any fitment issues with the barrel assembly fully seating in the action if removed and reinserted. Putting them under heavy tension with the tubes bonded on may have caused the above scenario??



What I have noticed.



Immediately apparent on the .22 was that indexing the liner went from a circular dispersion that was approx. 3 to 3.5 inches at 25 yards, to the liner with CF sleeve bonded on indexing in a single vertical line approx. 1 inches tall at 25 yards. NO horizontal dispersion at all.

The .30 displayed the same characteristic post sleeve bonding, but on a reduced scale. It indexed in a tighter circle from the beginning, and went to indexing in two distinct POIs at 25 yards that were about .5 inch apart vertically.



With the tensioning tubes bonded on, both rifles demonstrated less than .25 MOA deflection vertically at 50 yards going from bare assembly to hanging a Donny Ronin on the end. Previously, either rifle would display a change in POI of around 1 to 1.25 MOA at 50 going from bare factory shroud to Ronin installed.



The .30 was a drill from the get go, but I modded it anyways, since its purpose is 100 yard target shooting and I wanted to eliminate the droop that the Ronin imparted to the barrel. Droop being a clear indicator of 'floppiness' I decided to stave of the effect of any adverse harmonic activity.

The .22 always shot good, but displayed the same droop, so it got the treatment as well.



Non empirical and completely unsubstantiated, but my feeling is that the .22 tightened up at 50. It would previously shoot into a 1/4 inch as long as I did my bit, but the groups were always tidy little cloverleafs. Post treatment, it now stacks RDMs in a single ragged hole far easier than before.

Maybe I have been having really good days? Maybe I have been holding my tongue right? Maybe I got a killer batch of pellets?



My feelings are that it benefited from it.
 
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Addition to the previous post.



Both liners are STX Pellet A liners 700MM

.30 shooting 44s at 890

.22 shooting RDMs at 960



All measurements given in the post above are approximate as I am relying on memory. I suck at writing stuff down.....



Factory shrouds are getting the open bushing ends bored to .787 and will be reinstalled over the CF tension tubes to retain factory appearance.



Any questions or critiques, fire away!
 
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As to this recurring cost debate, an airgun that has as many parts to manufacture as the Impact is rightfully going to cost what it does to make. The new Maverick has fewer parts and shares several parts with the Impact. So, it is rightfully $500.00 cheaper to buy. Other airguns are made with far less parts but are hand-made and ported, polished and tuned, and are in demand. So, therefore, they command a good price. Other big -name companies mass produced with roughly the same amount of parts in cheap labor markets and sell for far less; go figure. The same principles holds true in the powder burner world as well when a low-end AR full of parts costs as much as a simple but high-end bolt action.

On another note of contention recently brought up, though some models are out of some individuals budget, and that sucks, a good platform of an inexpensive airgun can be made to get the job done just as accurately without all of the extra moving parts and bells and whistles. Those individuals are probably better off or in a better place in life than the guy who simply opened up the check book...
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The economics is likely much more complicated than simply looking at the number of parts. 

Two things come to mind: profit margin and perceived value. In both these regards FX is brilliant, from a business model perspective. Reduce the overall dollar amount (in this case by doing away with a real barrel but there's likely other ways this is happening) that it costs to produce a gun, while concurrently and aggressively acquiring industry figures (read YouTube) and paying them to convince people that FX guns are worth the price. End result of that game plan for FX is greater profits (through a more favourable profit margin and increased demand). Brilliant and should give any FX owners peace of mind since those are the types of business decisions that keep companies afloat.
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cost depends 100% on number of parts and cost of each part......

A small shop like FX with just about all parts parts made in Denmark ......

how come you don’t apply your theory to diana?.....

Do you own SPA made guns? .....

Then what’s wrong with pay people like Matt and Ted who actually contribute to the product design as product consultants, spokes person and ambassador ?....

Many people complain of corporate greed and the Chinese are stealing all the jobs....
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Wow, here goes:

As I originally said, the economics is more complicated than simply the number of parts, yes that's a factor but not the only factor. Dictionary search of the word "complicated."

Sweden my friend, Sweden. 

I didn't apply"my theory" (aka economics 101) to Diana because we're talking about FX here. 

Nope, I don't own any SPA guns. 🤔

I didn't say there was anything wrong with paid promoters, actually I said quite the opposite. Dictionary search of the word "brilliant."

There were no complaints of corporate greed and certainly no mention of Chinese theft of jobs. 

That's all. 

As for attempting to get the thread back on track......

Interesting to note that complaining of the 7/16 inch od Crosman barrels and calling them soda straw barrels was all the rage on the ole Green forum 10-12 years ago. Lots of people claimed those long skinny barrels were prone to harmonic issues as well as shifting pois. I remember seeing pics of people throwing three or four or more barrel bands on their Discoveries to try to alleviate the problem. Same problem, different manufacturer. 

There's another method that guns like the Veteran and Prophet and perhaps other bullpups use, and that is clamping the darned thing into submission. I have reviewed and own various guns wirh barrels that are either free floated threaded into the receiver and/or clamped to the air tube. In my experience, the common denominator for a gun that is devoid of poi shifts is a real barrel. 

I'll take my airgun barrels (meaning where I throw my hard earned 💰) free floated OR tensioned OR clamped OR threaded OR etc, as long as they're barrels of thick enough outer diameters to be structurally sound on their own and not prone to shifting poi. 
 
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Addition to the previous post.



Both liners are STX Pellet A liners 700MM

.30 shooting 44s at 890

.22 shooting RDMs at 960



All measurements given in the post above are approximate as I am relying on memory. I suck at writing stuff down.....



Factory shrouds are getting the open bushing ends bored to .790 and will be reinstalled over the CF tension tubes to retain factory appearance.



Any questions or critiques, fire away!
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I literally just tried my 700mm .25 impact with the carbon liner sleeve and boy did it tighten up the groups at 100 meters!! Also tried the tension spacer but didn’t like it. I was thinking about the barrel sleeve and why didn’t I think of what you did, just epoxy it on too!!! Although there is a bit more commitment on that one since that means I can’t install the shroud at all. 
 
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Addition to the previous post.



Both liners are STX Pellet A liners 700MM

.30 shooting 44s at 890

.22 shooting RDMs at 960



All measurements given in the post above are approximate as I am relying on memory. I suck at writing stuff down.....



Factory shrouds are getting the open bushing ends bored to .790 and will be reinstalled over the CF tension tubes to retain factory appearance.



Any questions or critiques, fire away!
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I'm really interested in the open bushings ends. Can you share photos of how they look before and after installing them on the barrel.
 
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The tension tube absolutely makes the entire barrel assembly more rigid, and bonding it on serves to eliminate any possibility of the components expanding or contracting at different rates I believe.

Both rifles being zeroed and going from a 70 degree F. environment to a 40 to 45 degree F. environment for range time, I noticed no POI shift whatsoever. That is as much proof or evidence that I have so far. 

I LIGHTLY tensioned them while the epoxy cured so that they were butted square to the front barrel block on the rifle and seated with zero gap. While I did tension them quite firmly to test the holding power of the barrel set screw, which I found will take a considerable amount of tension and not slip, I was concerned that once everything was cured the barrel would not seat fully into the rear section once removed. There was a bit of squish present when tensioning them firmly, so I backed off to a light tension.

The barrel set screw on both rifles did not slip a bit while doing this, and I believe that you would have to purposefully go at it like a gorilla to unseat the barrel from its seated position with the set screw tightened. It stood up to a fair ammount of force screwing a Donny on to the barrel retention nut and seating it very firmly.



The shrouds are not done yet. They are too long for my Taig Micro Lathe, so a friend is boring them for me on a lathe set up to use a collet.

The tension tubes that I received measured .785 on the OD, so I am having the open bushing ends bored to .787, which is a standard tooling size, for a slip fit over the tube OD. The open bushing end being the end that slips over the factory FX barrel assembly, not the threaded end for the moderator.

Once done, they will reinstall over the CF tube, retaining factory stock appearance and allow me to continue to use my FX threaded Donny FL end caps instead of changing the end caps to 1/2- 20 caps. They will also serve to disguise the CF tube mod unless studied closely, and that will serve to keep the gang guessing as to just what kind of Voodoo I worked on my rifles!
 
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I'm not a engineer, so can someone help me understand the proper definition used in the process of bonding the CF over the FX or any barrel. what are the actual forces being applied? 1-Tension, 2-Compression, or just stiffing, dampening of the barrel?.

I thought the original design of the FX system (especially the light weight version) was to use the larger Dia. sleeve to help support and dampen the liner while allowing for easy liner changes.

I would just add one or more factory supports for more stiffness, also this would allow for some harmonic adjustments and tuning as well.
 
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Stiffening only, the way that I did mine. Using only the liner sleeve, you are adding stiffness or rigidity.

Putting tension on the larger outer tube would add both stiffness and tension.



The CF liner and tension tubes are not designed to work with the Super Light barrel system, and from what I have seen in a 700MM .30 Cal. It does not need the help. Truth be told, the 700MM STX barrel in .30 Cal. was fine the way that it was, I modded it because I could and wanted to experiment to see if there was any benefit. There was a benefit in both calibers on the Impact, but the difference seemed to be more readily noticeable in the .22.



As far as re tuning, none was needed for me. All settings on the rifles were left as they were prior to the mods as a baseline.

I re zeroed the optics to account for whatever difference in original POI occurred due to barrel removal, and to account for the lack of droop present now with the CF making everything more rigid. Both rifles settled in and began making tight little holes that made me smile, so I called good enough and had a sandwich.
 
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The whole idea of sleeving a thin barrel in carbon just seems really odd. How do know the barrel is perfectly straight for its entire length? How do you know the carbon tube is perfectly straight for its entire length? Do you put them on a device to test for straightness or run-out? What if the carbon is straight but the barrel not straight..or vice versa? What if both are not straight? Do you spin the barrel/carbon assembly to insure the epoxy or whatever is used to bond barrel to carbon does not settle while it cures?

You could possibly straighten a "bent" barrel if it were really thin. A carbon tube is either straight or it isn't..you cannot straighten carbon tubes. Carbon tubes do flex. If you insert a bent barrel into a carbon tube, there will be tension or torque applied from the barrel to the tube or tube to barrel depending on which is more or less straight. If the barrel imparts pressure on the carbon there is going to be uneven amounts of epoxy surrounding the barrel. The area with different epoxy thickness is going to have a different harmonic than an area with "perfect" epoxy.

Over-thinking it...
 
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... A carbon tube is either straight or it isn't..

...Carbon tubes do flex...

...uneven amounts of epoxy surrounding the barrel. 

...The area with different epoxy thickness is going to have a different harmonic than an area with "perfect" epoxy.

Over-thinking it...
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This 👆

I know a littlebit about FEA (finite element analysis). We cannot predict how the composits will behave, but we can measure the end product = a CF tube.

Couple years ago I've been involved with a designing a "machine" that can "read" oscillations in CF tubes. I am talking about a need to understand the numbers.

In our interests were sorting and tuning CF tubes by the measured numbers.... used in archery (arrows), golf clubs, fishing rods.

To keep the story short,

- when the operator mixing up a compound, even in a same manufacturing facility, he puts a single spoon more or less powder yesterday vs tomorrow you got different specs...

- all the CF tubes are made on mandrels, wrapping process, you change the turn direction CW vs CCW you got different specs...you wrap the fiber softer or stiffer you got a different specs...

- some tubes, from the same mix, from the same mandrel, some are cylindrical grind some not...you got different specs...

Now we got to mathematics/physics...every tube have two node points (look it up what that means), and at least one stiffer side and one weaker side. Now depend of a batch some may have multiple stiffer or weaker sides along the length.

So I made a testing fixture - for my competition arrows because every boxed dozen have about 2-3 not matching a majority. I had to measure at least 5-6 dozen blank shafts every season to have a matching let say 3 dozen arrows...sort them by amount of flex and indexed/marked the stiffer/weaker side and only then started fletching and assembling further.

And then we developed a testing machine for golf clubs and fishing rods, you can look it up on youtube how much the CF tubes can flex....

And now you want to bound the CF tube with your liner? Sure you can do it, but your results will for sure vary from Ernest or Joe or Michael.

The tube material is coming from different batches, different timing and places, you cure at 20C or 25C, did you index the liner first,,,,and so on.

Will you like the final result? Why not...

So everything comes down to a boiling point you do it or not do it...I don't think you will have comparable results to your very first neighbour...will or can it float your boat? Sure, why not...

This is my best educated guess, go for it and tell us the story, picture your score card to believe.
 
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