Crusader Arms Crypto

PinaKaleada said:
How did you go about pinning the FSB and keeping it straight?
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Make sure your barrel nut and handguard cap are on the barrel, then prepare the FSB. I threaded the hole underneath the sling swivel for a 10-32 set screw, mounted it on the barrel, against the handguard cap and aligned it best I could by eye. I used a detachable carry handle to help align everything by eye, then I took the rear sight out and used a pipe long enough that it could sit on top of the carry handle and almost touch the FSB, and made sure it was pointing directly at the front sight, once it all looked straight I tightened the set screw. Small levels and small machinist blocks can help make sure everything is straight, you can put a machinist block on top of the rails on the upper and use that to help align it as well.
Then I took another piece of pipe that was wide enough to fit over the muzzle and long enough to press against the FSB on one end and be held down with a washer and flash hider on the other end.

Double check everything to make sure it is level and then find the middle point of the 2 flat spots where the pins will go through and mark them with a center punch. Get a really good drill press or mill and make sure that the barrel is level and the FSB is perfectly at 90 degrees when you are putting it in the vice. You can also use spacers to support the side of the barrel that is not in the vice, so when you are drilling its supported from both sides (bridge vs diving board).

Drill one hole at a time and start with the one closest to the bayonet (so you don't hit the set screw) using a good quality, new #31 TiN coated 135 degree point drill bit. Use lots of oil and go slow during this process, if the barrel has a nitride coating it will be more difficult for the bit to cut through, remember to remove the burrs often. Once the first hole is drilled you are going to use a 2/0 straight flute hand reamer to ream the pin hole until the FSB pin only sticks out 1/8". Go slow, use lots of oil, clean the burrs often, and only turn it clockwise, even when you are removing it from the hole. Make sure you do not ream go too deep. Once the FSB pin is sticking out 1/8" you will need to pound it in the rest of the way with a hammer and punch. Remove the set screw and do the same process to the other side. If you did everything right and took your time you should have an aligned FSB, if it's off by a degree or so don't worry too much. Make sure the rifle cycles and its getting gas through it, and make sure you can sight it in and you are all done.

Take your time making sure everything is level and on straight, and don't forget the handguard cap. It is a fun job
 
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