The POI shift is rather a relative thing.
For casual shooters and most hunters the slight POI shift is not a problem and might not come into their attention, hence they might not notice it.
While for keen precession shooters I mostly find that even a slight POI shift is a big problem.
Then there are again two scenarios. One scenario is this that the shooter always re zero the gun for every new session. Once it's done, there is no issue for that session.
The other scenario is in which the shooter doesn't re zero the gun for a new session. Here the issues and comparisons start.
As per my experience, Royal 400, Royal 500 and Boss keeps the POI as close to any last session as it is possible without the need to re zero the gun.
There are other external factors that can still affect the POI very slightly which are change in humidity, temperature etc. These are constant factors for all kinds of guns and all kinds of barrel systems.
FX liner system is made up of a number of parts i. e. Liner, rear retaining part having transfer port, front retaining nut, outer shell of liner and O rings. These were the parts when the liner system was initially introduced.
Later Ernest Rowe started inserting a carbon fiber tube between the liner and the shell and epoxied it. Definitely this had been done to fix some inherent issues of the liner system which is most probably POI shift.
Later FX also started selling carbon fiber pipes for this purpose.
Even later Ernest Rowe and mny other tuners started tensioning the barrel in FX Impact.
Later FX also started offering it.
So the improvements in the liner system went on and on.
In my experience, the free floating barrel keeps the best POI provided the barrel is solid.
FX makes wonderful liners. When I convert these liners into a solid sturdy barrel, 95% of POI shifts are gone. But then I have to prepare a separate complete barrel in which I cannot replace the liner. For some other liner I make a new complete barrel using that liner.
I am also using some real solid barrels in Impact and get good consistency of POI.
Further the tolerances of each gun are different hence some face more issues than others.
I understand that one of the reasons of keeping the liners inside the cylinder or plenum in Panthera and DRS is to avoid POI shift.
Almost all the PCP models of FX are currently being made on liner system. So changing the liner system means redesigning of all the models of FX as far as the balance of the gun is concerned.
The liners are very accurate but are mostly unsuccessful in creating a consistantly precise and accurate truck gun.
Many users having liner system using the gun in their trucks complain about this issue while similar users of Cricket or RAW do not face this issue.
Bhaur