FX M3 POI Shift (With vs Without Shroud)

[bigHUN]

Back in time somewhere early 2020 when I got my MK2 I was reading modding posts here @ AGN, and I made those changes myself as well.
First, how many orings outside of barrel in between blocks? Kind a lazy to brows for the BOM (bill of materials) but I guess 6 or 7 orings. The factory specs is NBR 70 change those to 90. A bit harder to push in the barrel but with some patience you will be good. You cannot expect a same softness/hardness oring will perform the same up her in Canada or down South in much warmer climate . Change the material to your situation.
Second, do the same inside barrel, I put an oring on the liner every 100 mm.
Third, make a small cone on muzzle end also inside liner nut, and when you tighten the concentric will sit in same centerline. Wrapping a teflon tape is almost the same but less convenience.
Forth, torque the nut the same and mark the position with a line. I made myself a two fla socket wrench for my torques screwdriver and set it to 1.70 Nm. Works for me.
There are more but need a coffee first

 

[RickH]

Every gun is different. Five rifles built and set up identically will shoot differently. One will like one pellet and the next two are awful with pellets from the same tin. True of powder burners also. Looking at a single gun, ask yourself what is different and how might that change have physically affected that gun? You removed a suppressor? How is the gun physically different? Use a different supressor? How is it different from the other? How is the gun shooting differently? Whatever you do, only make one change at a time and see how that change works. Keep track of every change and results. Don’t get in a hurry. It may take some time and quite a few shots but once you get a routine going you’ll solve these problems more easily.

Rick H.

 

[Triggers and 4X4s]

When I bought the M3 I fitted the carbon fibre barrel sleeve. My M3 came with only 2 o-rings installed on the barrel liner.

Remember the shroud screws onto the front barrel liner lock nut - Therefore If you tighten the barrel liner lock nut only slightly then the shroud will tighten the barrel liner lock nut further when you put the shroud on and hand tighten the shroud.

I think what I am experiencing is torsional deformation caused by torque force applied to the barrel liner lock nut acting on a hollow rod (The barrel liner).

This is normal but as mentioned the shift of the POI by 1.2 inches at 25 yards does not seem normal to me.

 

[Bobbybeef]

I JB welded my carbon fiber sleeve to my liner in my FX Crown and then proceeded to index and the POI varied 5/1/2" at 35 yards and I kept the group that hit closest to the center of the oray of groups which is WRONG from a reliable person. They said I should have picked the tightest group, which was actually 5 pellets in the same HOLE no deviation I was shocked so I am going to reindex at 50 yards and if I get to a group that shoots that tight, I will stop and leave it there! The gun is a 177cal. crown about a year old. I glued a sleeve onto the liner of my other crown 22cal. I shot it at 35 yards and the group was 3/8" I will index that one next. When I redo the indexing for the 177cal. I am going to take pictures and post on the forums to let people know what can be done.

 

[qball]

Good point and exactly what I was thinking at the range. I did exactly what you suggest, results were still the same ie no change.

This is definitely puzzling, can't really think of other reason for it. Are the grub screws for the barrel tight? If you look through the shroud is there anything out of place? Maybe try another liner/barrel somehow?

 

[Triggers and 4X4s]

I could find nothing unusual that I could spot visually.

Yes. My next steps are to test with a second barrel liner and shroud.