Cricket Bullpup .25 POI shift, Help please

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mubhaur

mubhaur

Member
Nov 8, 2015
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Karachi, Pakistan
Dear Friends,

I have been facing POI shift in Cricket .25 bullpup.

I have tried many combinations of torque on all the 4 screws of the clamp that hold barrels as well as cylinder.

Just a little bit of success but not more.

Gun is very consistent in FPS.

At 50 yards, the POI shift is around 1", stays there for a couple of days and then shifts again.

I need advice that what more can I do to eliminate this POI shift.



Regards,



Umair Bhaur




 
Is this a new gun to you? Has it done this before? Could it be the scope?

Is the temperature where you live changing? Sometimes temperature changes will affect POI. It happened to mine. I placed an Oring between the shroud & the Breech block. This fixed the problem. 

Have you chronied your speeds? When this is happening? Rule out any regulator problem. 

Just some thoughts and ideas. 
 
Upvote 0
Sounds like it could be a scope issue. Those inner tubes are bouncing around. I had a cheaper quality scope once that would bounce around and shift POI. When it was on the bench, it was fine. The second I moved it around, shook it, bumped it, the POI shifted. It was not a lot but just enough to frustrate me. If you have not ruled out the scope, my advice: find a scope that you know does not do this, put it on the gun, and see it this continues. If is still does, then you can elminate the scope and start only focusing on a gun. 
 
Upvote 0
4 things. More or less I have found to be the cause of my POI shifts.

1) what pellets are you using? same every time? Head size them, use the same size for a few days.

2) clean the barrel. THIS the big one besides a scope issue. I recommend ballistol and use a patch worm or crown saver style of cleaning system. See TominCO (tomcat video) on cleaning if not familiar.

3) check the shroud is tight

4) mechanically center your scope reticle. Shoot for a few days bang it around and see if it still moves. If it does not you might have your turrets so far out of adjustment that the rector tube is free floating. (or swap scopes)

good luck.
 
Upvote 0
Yes dear friends,

I am back.

I live in a coastal city so the level of humidity often changes here. Sometimes dry and sometimes humid.

I use 34 grain jsb at around 850 fps. Barrel is clean and shroud is tight.

Scope is not perfectly optically centered but also not to the limits. I understand that since PCP has little recoil, even if the scope is not perfectly optically centered, it should not change POI.

Scope is Discovery HD model.

Already replaced rings and scope as well.

Everything looks tight.

Holds POI for a couple of days and then shifts.

Thanks for the advices.

I appreciate any further advices.

Regards, 



Umair Bhaur 
 
Upvote 0
Also have you shot entire strings over a chrony and got consistent velocities?

If the gun still shoots badly without the barrel shroud then...

Remove the barrel and put it back in and be sure to tighten the set screws.

Also after removing the barrel this video is worth watching...

https://www.bing.com/videos/search?q=airgun%20cricket%20barrel&qs=n&form=QBVR&sp=-1&pq=airgun%20cricket%20barrel&sc=0-21&sk=&cvid=B22A21B4EA664CE59217146455AB3E52

Though it may not remedy your shifting POI, it may give you better accuracy.



CA
 
Upvote 0
If by shooting it without the shroud does not help then it may be the varying pressure in your air tube which may require to do one of two things and isolate the barrel from the gun making it true free floating and or making the reservoir/ action free floating within the stock.



CA
Click to expand...

But how can the barrel of this bullpup can be made free float as the barrel is held only by means of clamps that also hold air tube?
 
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Dear Friends, 

Here is an update.

I removed the shroud. Zeroed the gun. But very next day it was shooting 1" right at 50 yards .

I cleaned the barrel and again started shooting.

The behaviour during complete strings is still unacceptable .

POI starts to shift right to left and left to right.

There is no up and down shift.

Shifting is only horizontally.

Changed scope and changed the mount but of no use.

I picked my Fx royale 500 .25 and royale showed very consistent behaviour .

May be due to free floating barrel.

I have also installed water level to eliminate chanting.

Please comment 
 
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