FX Stiffening Impact

Airmarksman makes the backbone and it's available on Utah Air. There was a thread on POI shifts a few weeks ago. The OP installed the backbone with good results. I dunno. I stopped reading the latest post on that thread. Check these threads:

 
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I went the DIY route on the cheap and my Impact is spot on shot after shot. I used a plumbing fitting painted black behind the shroud and tighten the shroud nut against it. That helped a lot. I also removed the liner O-rings and used painters' tape instead with just the right number of wraps in each section for a tighter fit but yet still able to remove the liner with only some added degree of difficulty. I use a printer halfmoon type barrel support under the shroud clamped to the tank. I put O-rings under the scope rail to push the shroud down against that halfmoon support. My last hunt was 13 headshots on squirrels back-to-back at between 80 and 85 yards over a three-day span. Mine is a .30 cal 700mm. My tune is right at a 1% ES and is tuned to 90 FPE. I did all of this because the CF tubes were all sold out at the time and didn't want to wait.
 
I went the DIY route on the cheap and my Impact is spot on shot after shot. I used a plumbing fitting painted black behind the shroud and tighten the shroud nut against it. That helped a lot. I also removed the liner O-rings and used painters' tape instead with just the right number of wraps in each section for a tighter fit but yet still able to remove the liner with only some added degree of difficulty. I use a printer halfmoon type barrel support under the shroud clamped to the tank. I put O-rings under the scope rail to push the shroud down against that halfmoon support. My last hunt was 13 headshots on squirrels back-to-back at between 80 and 85 yards over a three-day span. Mine is a .30 cal 700mm. My tune is right at a 1% ES and is tuned to 90 FPE. I did all of this because the CF tubes were all sold out at the time and didn't want to wait.
I think you might be on to something. The liner + shroud + stiffener leaves a lot of flex in the barrel assembly. Look at the RTI Prophet. Similar form factor of gun (bullpup) but much stiffer due to the LW solid barrel. A bonded carbon fiber stiffener applied directly to the liner might be better than the tensioner.
 
Airmarksman makes the backbone and it's available on Utah Air. There was a thread on POI shifts a few weeks ago. The OP installed the backbone with good results. I dunno. I stopped reading the latest post on that thread. Check these threads:



👆👆👆 Backbone!!!
 
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If you are referring to the barrel assembly I opted to use the Huma Tensioner kit and the FX Carbon Fiber liner. My barrel assembly is now very sturdy and I havent had any more poi shifting issues. If you are referring to the action/chassis I havent tried one but there are a couple different backbone rails available from Utah Air.
I did something similar, but used the huma tensioner and a modified carbon shroud and liner from bullet central. Much quieter with the shroud installed.