On my Airforce Texan .510 cal 34 inch factory barrel i have achieved decent accuracy from factory barrel after hand lead lapping and putting a full diameter carbon sleeve from factory barrel diameter to full one inch or 25mm to fit tight in the frame to the barrel bushings held in tension with a Donny FL Emperior with fast detach..It is also glued to barrel with high strengh 3600 psi glue.. It has worked out good over the years of use..I found carbon fiber tube 26mm to 32mm diameter and was thinking of putting on another sleeve to the frame and donny fl emperior at the exact length..its only $25.00 for the 32x26mm carbon tube..I am going to try it out without glueing and see what happens..My Texan has lots of vibrations maybe it helps to stiffen the whole frame barrel moderator system..Im so happy carbon fiber is getting so cheap..I really do need the weight savings as i age...Thanks again AGN friends