FX FX Impact Barrel Indexing ?

Is your scope canted?

Hello!

You need to remove the tensioner system, yes.
Test fire a few shots for group, then remove the shroud and threaded liner piece, make a turn to say 3:00 o'clock, reattach the threaded liner piece and shroud, then test fire again. Repeat this until you find what would be called TOP DEAD CENTER during the clocking.
Leave it there but mark it for future reference so that you don't need to repeat this operation.
Pretty easy!

mike

Can I give you an idea where to look for those L-R offsets when you shooting different distances?

The Impacts, at least my MK2, has the upper scope rail = floating. Clamped with 3 screws. By default not necessary follows the barrel centerline.

That upper scope rail we supposto tune if we planning shooting for multiple distances.

For example test this if you place a paper with a vertical line @ 10 meters also @ 50 or 100.
Shoot 2-3 shots each distance without touching the scope and the rail. Any offset to the line? and you will know where you need to move the upper rail.
You cannot do this rail alignment in your basement ballpark it with a lazer, that won't be enough precise past 50 or 100 distance.

When you start alignment tuning that rail, you will need to go there and back several times shooting at short 10 meters, don't touch the scope and shoot 100 meters. Adjust. there and back until both of these distances centers on the vertical line.

I have several liners, I am usually indexing new liners @ 100, the Impact resting on mechanical rest front and rear as well.

Get rid of the barrel tensioner. When you tension the barrel, I believe you bow the liner. I had same type issues, and went back to stock shroud, shoots straight again.

I normally go around 25 yards, I can see the small groups without needing binos at that range. You'll likely end up with a basic circle as you move the liner to each new position on the "clock". Always using the same hold point, which I failed to mention in my previous post (oops).
I would also not tighten the liner nut too hard in between shots and also at the final location. Tightening too much can stress the liner (similar to what cahil_2 stated).
There are also other posts on this subject if you care to do a search.

mike