FN FiveseveN Forums - Taking off the barrel to SBR the PS90

Posted by CLC3251:

FN FiveseveN Forums - Taking off the barrel to SBR the PS90: "First remove the pin holding the flash hider on. You can grind out a relief cut as Mark did or drill it out. Either way, remove the entire pin. There is no way to do it without maring the barrel extension. If you took a really long time, you cold carefully drill/grind away the opposite side of the sleeve from the pin and carefully drive it out. Once the pin is removed, don't try to unscrew the flash hider from the sleeve, it will not come out. Take a 15mm open ended box wrench and grind down the sides so that it will fit in the groove in the chamber end of the barrel. Most standard wrenches will not fit as the groove is tight and if you try to force it you will mar the barrel. Unscrew the barrel from the flash hider. It has left hand threads, so turn it clockwise to remove it. An easy way is to wrap the flash hider in a few layers of paper and clamp it in a pair of aluminum AR-15 barrel blocks to hold it without marring it. Watch the front of the receiver as once the hider/sleeve unscrews a certain amount, it can rotate and scratch the front of the receiver. Once it unscrews from the flash hider, you can pull the hider/sleeve off of the front of the barrel. Watch carefully as there is a spring between the sleeve and the receiver around the barrel that you will need to put back when you re-asemble or replace with a short barrel and hider. Pull the barrel out of the back of the receiver carefully as the recoil spring is around the barrel and the spring loaded takedown button is near the back That's it. You can separate the flash hider from ther sleeve by unscrewing it but it is right hand thread so unscrew it counter clockwise. The two different thread turns is what prevents you from unscrewing the hider first. The barrel only screws into the flash hider, but the flash hider screws into both the "