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Posted: 6/16/2006 3:48:33 AM EDT
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I want a FSB w/ bayo lug on my postban MT6601. how do I replace my postban FSB with a real man FSB? I mean if I buy one of those undrilled FSB how do I know where to drill the holes for taper pins? I know it's hard to do but I can't send my upper to ADCO since I live in Italy, also I can't buy a new barrel due to Italian gun laws. of course I'm not going to do the job myself. |
Frens- You are going to need a new FSB (obviously) and a milling machine to acomplish this. Then you need a 2/0 taper pin reamer and a 1/8" drill bit. Tap the hole on the bottom of the new FSB for a setscrew. You may have to remove the sling swivel rivet to access the hole. Pop both taper pins loose, but only leave one of them in place to position the FSB on the barrel. Clamp your barrel in the mill so the FSB is perfectly horizontal. Use the taper pin reamer to center up over the empty hole of the FSB. Without removing the barrel from the mill, remove the other taper pin and the FSB. Slide the new FSB on to the barrel and position it perfectly horizontal like the old one was. Use the setscrew you added above to hold the FSB in place. Carefully drill through the FSB. Beware that the drill bit acts funny when you are in an interrupted cut which will be 2/3 of the job. Now ream the hole for a taper pin. Remove the new FSB and swap back to the old one. You will probably need to add a setscrew to the old one now too. Install the old one with the same taper pin that you used while locating the first hole. This is the reference to be sure it's in the right place. Now tighten the setscrew to hold the FSB into place and remove the taper pin. Align the taper pin reamer in the 2nd hole. Swap the FSB again, drill it, ream it and you are done. Yes, it's a serious pain-in-the-ass job. That's why we build special fixtures for it... |
wow Randall! thank you so much! that really seems like a pita but I'll try it |
Fixed it for you! I would be happy to never do another FSB swap in my life if I could get away with it. Of course I will do them as well, but it's MUCH easier to install new ones on new barrels than on used barrels which have been drilled once already. |
I don't have any pictures of mine, but imagine a fixture that holds the barrel at the barrel extension and at the gas block seat. This allows you to repeatably clamp the barrel in place and locate the gas port and taper pins consistently. It also holds the FSB at the proper location so it would not be leaning left or right. |
I have a FSB that I had to cut off a barrel with a permanent flash hider. I could send you the bottom piece with the lug... |
thank You Randall, but I guess shipping would cost more than the lug  I'm going to replace the FSB as soon as I have it. I'll try to do the work...if we see that is't impossible to do maybe I'll cut the lug and I'll weld it to the old FSB even if I don't like this idea too much. |
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