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Posted: 12/6/2004 4:56:46 PM EDT
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Looking for some expert advice on the correct procedure for replacing the front sight housing on the AR-15. Even though I know it will turn me into a homicidal maniac, I want to replace the housing bayo lugged version. Is this something I should undertake as a novice? If so, what are the pitfalls and watch-outs on something like this? Bent pins? Gas holes not lining up? Sight cant? TIA for the info. |
| It is a gunsmith task. Each barrel/FSB combo is drilled assembled, on a jig/fixture, so each barrel/FSB combo is unique unto itself. Swapping a FSB from one barrel to another is really not an option. To install a new FSB on an existing barrel, you would have to have the jig/fixture that would hold your FSB properly indexed to your gas port while you drill and ream the new taper pin holes. Not your average DIY home gunsmithing project. |
Ah, yes the setscrew method. This works great, but provides you with a FSB that may or may not hold zero if it takes a heavy hit. For the casual shooter that must have the bayonet lug (sounds a bit like an oxymoron, but hey, it's your equipment), this setup will more than suffice. For anyone who plans on using their rifle in rigorous competition/battle and especially if you plan on using that bayonet lug, this application will not work in the long run. BTW, getting those slots exactly right on your barrel, where the setscrews will seat as shown in the picture, takes precision measuring equipment and a mill. |
| ADCO will put your FSB on for you for $40. They did a nice job on my rifle, and they have an excellent reputation. |
A Colt will usually go onto another Colt, and a Bushmaster will usually go onto another Bushmaster. I am not sure about RRA. I would imagine that they would drill them at standard locations in relation to the other barrels of that type; carbine, midlength, rifle. So maybe the best bet is just to call RRA  P.S. You got me kinda interested. I think I will see if RRAs will match with other RRAs. I have 11 uppers to build tomorrow, and over half are going to be custom FF jobs that require the FSB to be removed. So I might know a bit more tomorrow, which is the goal for everyday in life, correct? 
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My experience has been different, 100% of the time. YMMV. There is no standard location even from barrels from the same manufacturer. Some are higher into the barrel, some are lower. Some are farther back toward the receiver, others are more forward. I would think that if you got two barrels from the same batch, you may be able to swap them, but with the millions of barrels out there, it is highly unlikely. |
I guess its a hit or miss thing, I one Bushy FSB I tried to swap would not line up, But the 3 of 4 Colt FSBs I have swapped around all lined up properly, Proof of Colt quality? Just Luck? I have no Idea! |
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An option for the DIY is to go oversize. Use #4 taper reamer and taper pins. This works on undrilled or used FSB. The jig is real easy to set up, just use 2 V blocks to support the barrel, a laser to index the extension pin to the front sight, drill, ream, and pin. BTW, on the set screw FSB, make sure to use locktite. Nothing funnier than the front sight wiggling while you're shooting or having the whole assembly come off after bayoneting a tree. Seen them happen and I still smile thinking about it. |
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