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Posted: 2/27/2009 8:03:34 PM EDT
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I need to install a FSB on a new barrel that has never had a FSB. Can someone run through the alignment and drilling process for me so I don't screw it up?
Thanks! |
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I have a Bridgeport and I am a tool and die maker so I am sure I can get it done. I just want to do it correctly. So what is the correct "tooling"?
I’m not sure that’s a job for someone to tackle who doesn’t have the correct tooling. You might be better off sending the barrel and FSB out to have the work done for you. ADCO would be my first choice. |
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I have a Bridgeport and I am a tool and die maker so I am sure I can get it done. I just want to do it correctly. So what is the correct "tooling"? The Bridgeport, although helpfull, isn't the answer to getting it right. A jig is needed and the cost of one {if you can find one} I would be guess to be more than a barrel. Every manufacturer is using almost the same FSB forgings. How deep the pin is set into the barrel is mostly a function of how each company made their drilling fixture. Some choose to put the pin in the middle of the pad on the FSB forging. This works great on 0.625" barrels, but leaves the pin WAY too high on 0.750" barrels. Colt pulls the pin down as far as they can to ensure that the whole pin is not going through the barrel. The latter is desireable as it helps create a better seal at the FSB-gas port junction. The pin being partly in the barrel and partly in the FSB makes the taper pull the FSB forging DOWN as you set the pin into place. The closer you get to a 1/2 crescent cut, the more of this benefit you get. 
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Flashbang - GREAT info! Thanks. The only reason I mentioned the Bridgeport is that it serves as my precision "drill press". I can build the jig to keep it square, no problem. I really appreciate the helpful pics of the normal setup. The one thing you didn't mention is the existing tapped hole in the FSB sling swivel slot (I have some FSBs with a tapped hole and some without). I was planning on inserting a set screw in that hole to help keep things snug and tight and drilling/reaming the front hole first, inserting the tapered pin then removing the set screw and finishing the rear hole. I guess it would just be a little added insurance.
After mulling over your comments on the positioning of the tapered pins with regard to snugging the gas port seal I may just re-install a set screw back in that hole when I am done to help accomplish that goal (that may even be what the tapped hole is for, I am not sure). Again, thanks for your helpful response. Regards, Mil-Surp 
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Quoted:
Nice, That looks like it works well for alignment. Are you using that as your sole clamp also? It looks like the FSB is just floating on the barrel and held in place by the bar? Basically just using the FSB as a pilot while clamping the barrel?
Here's my jig. |
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Nice, That looks like it works well for alignment. Are you using that as your sole clamp also? It looks like the FSB is just floating on the barrel and held in place by the bar? Basically just using the FSB as a pilot while clamping the barrel?
Here's my jig. Once its bolted up it doesn't move. You could tap the FSB for a set screw for some more security. |
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