FX Bhaur's analysis of POI shift in FX guns

mubhaur

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Nov 8, 2015
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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
 
I am shooting rings only, some at 50 meters but mostly 100 meters, with pellets -I gave up on the slugs years ago.
I have six liners in two calibers, 22 and 25, and I am swapping them. So I can say I had some learning curve with liners also power internals.
The POI shift is real for most people, but - can be controlled with some diy tinkering.
What can effect the POI consistency? I am not going to talk anything about how to tune the Reg for a given PowerPlenum performance...
A pure mechanical artifacts that can and will effect the POI shift
- node points
- shifting the liner and after couple shots the position settles
- rotation-indexing the liner around a clock
- tensioning the liner - consistency issues
- fouling-cleaning the liner
- seating the pellets
- crowning the liner
- Reg creep - effects the Valve
- Valve sticking - effects the Dwell
- oring sticking - effects many things
And the list goes on a lot of read on each of these, but lets not forget about reading the POA to POI artifacts....
Reading the POI, was that a flier or the the pellets hits consistently off?
and from here a new list is going on....

Ah, and I still forgot... is your scope/optics on level in quality?
or,
What about a "cold gun" recoil? I have that problem right now with my f-class 308 project...the barrel is solid and tapered 1.25 dia at the muzzle...

From my standpoint if a solid barrel would solve the POI shift vs liners - you bought a wrong airgun platform. Sell it and go get something else. And start all over again... ;)
 
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I am shooting rings only, some at 50 meters but mostly 100 meters, with pellets -I gave up on the slugs years ago.
I have six liners in two calibers, 22 and 25, and I am swapping them. So I can say I had some learning curve with liners also power internals.
The POI shift is real for most people, but - can be controlled with some diy tinkering.
What can effect the POI consistency? I am not going to talk anything about how to tune the Reg for a given PowerPlenum performance...
A pure mechanical artifacts that can and will effect the POI shift
- node points
- shifting the liner and after couple shots the position settles
- rotation-indexing the liner around a clock
- tensioning the liner - consistency issues
- fouling-cleaning the liner
- seating the pellets
- crowning the liner
- Reg creep - effects the Valve
- Valve sticking - effects the Dwell
- oring sticking - effects many things
And the list goes on a lot of read on each of these, but lets not forget about reading the POA to POI artifacts....
Reading the POI, was that a flier or the the pellets hits consistently off?
and from here a new list is going on....

Ah, and I still forgot... is your scope/optics on level in quality?
or,
What about a "cold gun" recoil? I have that problem right now with my f-class 308 project...the barrel is solid and tapered 1.25 dia at the muzzle...

From my standpoint if a solid barrel would solve the POI shift vs liners - you bought a wrong airgun platform. Sell it and go get something else. And start all over again... ;)
Agreed you and me can handle most of the variables to obtain consistent POI.

But when we talk about a gun we also consider 90% of the users who are not into the airguns in so much depth.

The point is that people using solid barrels in Impact have less issues of POI shift.
 
Another area of poi/poa is, coming under atmospheric, would be light changes- bright /dark, angle of sun, mirage. affects iron and scope sighting
Agreed I take all the common factors as a constant because these effect POI of every other brand too.

So I just discuss the POI shift in addition to other brands or in addition to FX Royal 400.
 
All a man has to do is own two airguns. One of FX’s known POI shifters and maybe a Cricket, Taipan or AAA. Possibly a BSA, AGT or Daystate. Maybe an Airmaks or a Raw. Either way, when the guy never has an issue with his one gun but does with the other, there’s nothing really to debate.

Had the same thought. You worded it less offensively than anything I could come up with.
 
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Had the same thought. You worded it less offensively than anything I could come up with.
When I see the new AGN member posting about the excitement of his new brand X, I think to myself, AGN has a new participant for a while. When I see a new AGN member post about the excitement of just ordering his brand new brand Y or Z, I think oh well, we probably won’t hear from him again after the honeymoon. Brand X is good for AGN business. And a lot of other businesses.

Edit: I had to leave work early and I’m sitting at home waiting to sign for a brand Y. Nobody on the forum will ever hear about it. Hopefully.
 
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... we talk about a gun we also consider 90% of the users who are not into the airguns in so much depth....
During more then 15 years in competition level shooting sports I have seen people new to the sport dropping $ six and seven figures on BNIB equipment, and that same equipment ends up in classifieds in next couple weeks.
Many people expect that their money will buy them guizmos that will work by itself.
Some can buy a Ferrari or Bugatti and ditch it in a very first corner.
Can't help.........

;)