Got my hands on an old Impact X, the barrel feel heavy compared to my M3's, wonder if its a massive barrel or maybe just the housing is massive and no space for o-ring/carbon sleeve, I'm not able to separate it, possibly because of a lot of loctite
Are you sure it is an STX and not an ST? The ST barrels are a single solid steel barrel which is rifled only at the end of the barrel. The STX is a barrel with a sleeve making them much lighter. BTW there is nothing wrong with the ST barrels. I regret having given up some. I would love to try a 700 ST with a tensioner and a harmonic tuner as a project.