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Posted: 4/10/2011 5:15:02 AM EDT
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I have a used A2 upper and FSB. I acquired a 16" barrel and have decided to build a budget A2 carbine.
http://www.armalite.com/images/Medium%20Images%5CRifles%5C15A2CBMEDIUM350.jpg My dilemma is the barrel has no taper pin holes and I'm not sure how I want to securely mount the FSB. I don't want to spend aot more money since this is an economy project. I have considered set screws in either the taper pin holes or two from the bottom. I'd like some experienced opinions here. Other options maybe? thanks db 
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The FSB is tall and thus creates a lot of leverage at the barrel attachment point if you bump it on something. This is the reason that the method of attachment is so critical. If the chosen method doesn't hold, your sights are useless and the gas flow is affected. If you're so inclined and have access to a drill press or mill, I would buy a drill bit and tapered reamer and install it myself.
or let someone with the know-how do it for you. |
| To be on the safe side drill and tap one ot two bottom holes as well as the four holes for the taper pins and then use set screws and you will be GTG. A drop of blue or purple thread locker or clear nail polish on the set screws will prevent them from loosening. I suggest you apply the thread locker/nail polish after you have verified the FSB is properly centered for the sights....<><....:) |
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Quoted:
To be on the safe side drill and tap one ot two bottom holes as well as the four holes for the taper pins and then use set screws Wouldn't that require drilling into the barrel to? He could just use taper pins then. I would drill and tap 2 holes in the FSB, and make 2 dimples in the barrel so the FSB won't move, and use loctite. |
I just used a custom mount I made in a CNC Bridgeport and indexed the center of the front sight post to within .0005 of the center of the barrel index pin drilled it out and taper reamed it. If you don't have access to do it right... I would just get the Armalite clamp on FSB. http://www.armalite.com/ItemForm.aspx?item=EU0240MPKIT |
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Quoted:
Quoted:
To be on the safe side drill and tap one ot two bottom holes as well as the four holes for the taper pins and then use set screws Wouldn't that require drilling into the barrel to? He could just use taper pins then. I would drill and tap 2 holes in the FSB, and make 2 dimples in the barrel so the FSB won't move, and use loctite. Not at all, no drilling into the barrel is needed. If the sling swivel has been removed just tap the hole beneath it (the hole that is exposed when the sling is removed) with an 8/32 tap and use a 1/8 x 8/32 socket head cap screw in to. On some already drilled FSB's I have been able to tap all four holes for 8/32 threads without drilling and some need to be drilled out a bit. Easy job then to just slide on the FSB (one that came another gun, whose holes don't line up with the ones already in the barrel) and tighten the screws to hold the FSB in position. One problem encountered by those who may have not drilled an FSB/barrel before is the possibility of drilling into the bore. Measure twice, drill once. Don't ruin a good barrel....<><....:) P.S. - the FSB is tapped, and/or drilled and tapped, while it is OFF the barrel of course.... |
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