i tried a bc shroud/tension kit on my 30 cal impact m3 and i had poor results, not to blame the bc kit at all, took me some time to regain some accuracy from my previous thought to be most accurate ag. (100 yard 5 shot group sub moa 
). im currently not sold on tensioning fx impact barrels, however what i did was put the bullet central shroud/tension kit on my same length 700mm 25 cal mkii. only a tiny bit short .05 inch rough estimate i put a oring to cover gap, not so much tensioned, only very slightly, my mkii dropping them in same holes as it has been known to do, i was shooting only 35 yards because of heavy wind but thats the thing, my most accurate 177 would stand no chance in this wind, 25 cal bucking the wind. im almost out of 30 cal pellets and to be honest i will never compete or have a need for 30 cal long ag. 
The mkii can rip that no problem i think, i prefer 33,95 jsb in 25 cal, i have a poop load of them in jsb or fx tins. my mkii impact does not disappoint, i have a friend a single father, who likes to compete, he uses the mkii only (as a control), i‘ve been takin down by him. its “his ag” when we shoot
). im currently not sold on tensioning fx impact barrels, however what i did was put the bullet central shroud/tension kit on my same length 700mm 25 cal mkii. only a tiny bit short .05 inch rough estimate i put a oring to cover gap, not so much tensioned, only very slightly, my mkii dropping them in same holes as it has been known to do, i was shooting only 35 yards because of heavy wind but thats the thing, my most accurate 177 would stand no chance in this wind, 25 cal bucking the wind. im almost out of 30 cal pellets and to be honest i will never compete or have a need for 30 cal long ag. The mkii can rip that no problem i think, i prefer 33,95 jsb in 25 cal, i have a poop load of them in jsb or fx tins. my mkii impact does not disappoint, i have a friend a single father, who likes to compete, he uses the mkii only (as a control), i‘ve been takin down by him. its “his ag” when we shoot