That may be true for the PCP you have in your hands, but grub screws bearing over rifled sections of the bore are very common in other PCPs.
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FX Lock this thread please- Discussed with Fredrik, there is no evidence of POI shift in FX barrel liner system
- Thread starter mubhaur
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That may be true for the PCP you have in your hands, but grub screws bearing over rifled sections of the bore are very common in other PCPs.
I don’t have one in front of me at the moment but the wall of the liner adapter for the .30 cal gets pretty thin. Just sayin’.
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In airgun land, a guy with a choke is focused on its diameter when he chooses his slug diameter. Problem is, you are neglecting the most overlooked important part of the whole process. Where it begins. Dirty air in front of your slug can be just as bad as the dirty air behind it that everyone is so focused on. No choke means you can start with a proper fitting slug from the get go. The fly in the ointment is you need a very consistent bore the full length of the tube to make the most of it. This might be where the liner is lacking and why it takes a choke to save the day. This might also be a factor as to why Bob has the best luck with a .218 but Bill thinks a .217 is better. They have the same gun and liner but it could be liner inconsistencies or how hard they are hitting them and the amount of dirty air in front of their bullets. The hole is deep. No one answer or solutions. Even when you do what I do and build a barrel around a bullet, there are still things that make you scratch your head at times. Bottom line, these are not powder burners.
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Thanks for the answer ; things are now much more comprehensible for me now . Yes , there are really a LOT of factors to tackle witn and make an airgun shine at the bench .
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Just remember, you only have to make it shine for a day to win a competition or film a glory video. Most of the frustration discussed in this topic is because guys believe their new mega airgun should do it every day under all conditions like a powder burner. Because that’s what they believe they saw or hear. Like a guy mentioned in another topic, we have to be aware of the half truths in this hobby. Some guns are just better at being consistent than others. But a gun with issues can still shine.
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My personal experience is that anything that touches a multi piece FX barrel system changes the point of impact. More weight more droop. Might still shoot good groups but it doesn't take much to shift the POI.
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Years ago I had discovered that the Impact's barrel liner nut was "sloppy" and caused POI shifts at each shot from barrel liner harmonic whip shifting the liner inside of the nut slightly. It made two distinct groups, back and forth with each shot. I did a write-up on it with my fix of wrapping the end of the barrel liner with Teflon thread tape so it takes up this little bit of space and centers the nut onto the liner and can't shift back and forth. It is less permanent than the epoxy.I have 5
FX guns , A Wildcat MK1 with the first concept of "smooth bore" , which means a heavy barrel , 16mm od , totaly smooth until the last 10 inches at the muzzle . Never had POI shifting issues , same with the Boss . Not the same with the Crown or the Dreamline. Maverick doesn't show a lot of POI problems , probably because the barrel assembly is kept in place in a stiffer way.
I've never put a lot of trust in the "liner in a tube in a shroud ", even in the Superlight system. Last week I put a Superlight barrel .30 on my Crown , and I had the feeling that the spacer , mainly the one near the muzzle , had not a tight fit with the shroud , so I modified the system . I machined a steel tube to go around the last inch of the liner with tight fit , and to go into the end cap of the shroud , also with tight fit and epoxied . So now the end of the liner is kept in place with the shroud in a very solid way . The first groups were very good .
The drawback of this setup : air from the liner cannot enter and expand into the shroud , so the gun is louder than before.
This is maybe not THE solution to decrease POI shifting problems , I just wanted to try something.
Oh yes , I get also 4 Kalibrguns ........POI shifting problems ??? What are talking about ?
See drawing below .
View attachment 428890
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Having only owned two FX airguns I am not one to speak overall on the brand but my experience of POI shifts turned me off completely to really try more (that and the general unfriendliness of their bullpup platform to lefty shooters).
First FX I owned was a Ranchero carbine. One of the most accurate guns out to 30 yards with the Smooth Twist barrel. One of those airguns you regret selling.
Second was a .177 Wildcat MKIII. This is the one that soured me. OOTB is was amazing. Single hole groups at 20 yards. After a few days the POI shifts started. And we're not talking 1" @ 50 yards. We're talking 1-2" at 20 yards. It would some nice grops at one POA and then all of a sudden the POI would shift 2" down and then stay there for a few shots. Then all of a sudden go 1" up and the right, then to the left, then up, then down - completely unpredictable where the next shift would be. Tried a lot to try and resolve but finally gave up and returned.
So IMO the comment that the barrel doesn't POI shift is accurate but a very subtle excuse for the guns issues. The barrel itself may remain very accurate - but the mounting in the airgun is/was causing unpredictable shifts that weren't for me.
First FX I owned was a Ranchero carbine. One of the most accurate guns out to 30 yards with the Smooth Twist barrel. One of those airguns you regret selling.
Second was a .177 Wildcat MKIII. This is the one that soured me. OOTB is was amazing. Single hole groups at 20 yards. After a few days the POI shifts started. And we're not talking 1" @ 50 yards. We're talking 1-2" at 20 yards. It would some nice grops at one POA and then all of a sudden the POI would shift 2" down and then stay there for a few shots. Then all of a sudden go 1" up and the right, then to the left, then up, then down - completely unpredictable where the next shift would be. Tried a lot to try and resolve but finally gave up and returned.
So IMO the comment that the barrel doesn't POI shift is accurate but a very subtle excuse for the guns issues. The barrel itself may remain very accurate - but the mounting in the airgun is/was causing unpredictable shifts that weren't for me.
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When you say "barrel" in reference to an FX barrel assembly it must refer to all parts of the assembly. Otherwise you could argue that the liner itself doesn't cause the POI shifting. The problem is with all the parts combined in normal use of the air rifle.
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I remember watching a Matt Dubber video and how he explained that Hein Frommann, a man whose ballistic credentials seem impeccable, developed the tension system. I don't believe this was an FX innovation, but is something they adopted. Full disclosure: I bought one, tried it, removed it. It doesn't tension the barrel liner (the thing with the rifling), it tensions about half of the barrel housing, the half at of the muzzle end.
Beyond that, I don't think we can point to every new innovation FX develops or adopts as "proof" that they know there is a flaw with their system. Could one say the same about the auto, aircraft, and computer industries for the last 50 years?
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I suppose there must be a good engineering reason why the barrel cannot be pinned at multiple points, not just a single screw near the breech.
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It should be very frustrating to buy any type of high end expensive rifle that some people call them “boutique airguns” and encountered all this issues, this is why I always step away from them and prefer to purchase any affordable airgun that I can tune myself without having all this hazel. This is way currently own four Avengers two .22 and two .25 cal one first gen and three second gen X and all of them are shooting flawlessly and very accurate.
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