So I took my AR into a small shop for a (thought to be competent) smith to install a free float quad rail and replace the front sight and "re-weld" the flash hider back on when done (weld needed due to a 14.5" barrel). Keep in mind this gun was grouping around 3.5"-4" at 100 yds last time it was shot 2 weeks ago. I got the rifle back last week and took it out today. Starting @ 25 yds I had to crank the rear sight post all the way to the left @ 25 yds., in order to get a 3 shot group all in the red. Next I moved it out to 100 yards. I couldn't even put one on the paper!!! We had 3 other ARs with us so No, it wasn't the ammo, No, it wasn't the shooter (I shot deadly accurate out to 200 yds with a LWRC piston op. . . barrels of fun too!!!) and No, it wasn't the sights. The front post is attached to a fixed piece on the barrel and the rear was on the same "T" mark that its been on since day 1. It seems that SOMETHING GOT PUT BACK TOGETHER WRONG?!? The so-called gunsmith that worked on it offered to "take it home and see if (he) could get it lined back up". I declined and will be taking it to a man with about a decade more AR-15 experience than I have on Tuesday. He's no smith, but I trust him to at least trouble shoot it. IF ANYONE HAS HAD THIS PROBLEM OF A SIMILAR ONE, PLEASE SHARE! I'M WORRIED SICK!?!