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Posted: 4/29/2005 10:45:58 AM EDT
| I was helping a friend of mine swap out the front sight on a Bushmaster Dissipator for a milled front gas block. The one he bought he got off of eBay (because he could not find the part in the bushmaster website or catalog), and was under the impression that they should all be built to the same mill-spec size, however the pin holes did not line up with the mounting holes on the underside of the barrel. I think it is obvious that he got a bad part, but why did they not line up; does colt or armalite or another manufactuer have different spacing, or is this just a bad part? Does anyone know where to buy a basic milled front gas block, as he is not interested in anything with rails, etc, and he lives in Jersey, where bayo lugs are still banned. |
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Gas blocks are match drilled to the barrel. i.e. they are installed and drilled together. Changing pre-drilled gas blocks almost always ends up with a misalignment of some kind. (Ask me how I know..) Edited to add: You can drill out the holes in the gas block and tap to 10-32. By using set screws, they will go into the barrel pin holes and you have enough adjustment to keep it aligned. |
| As Southern Raider said, most holes drilled to pin on sights, even done by the same manufacturer, won't line up with sights that have already been drilled. Drilling, tapping, and installing set screws as suggested works well, and if the holes aren't TOO far off they can be opened up to a slightly larger size and have larger pins installed. |
I got a JP Enterprise adjustable block (with a rail on top) that uses 3 set screws on the bottom...bonus part is that it's slightly longer than the original and completely covers any old pin holes. Bogus part is is that I had to dimple the barrel for the set screws to really seat.....oh well. I used enough red loctite on to keep it in place that I'm gonna have to use a cutting torch to get it off if I ever want to go back to original configuration
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Since there is no spec for where the two holes are drilled, chances of finding a FSB or gas block that will line right up are slim. Even if you have a rifle from a certain manufacturer and a FSB from the same manufacturer, it probably won't line up correctly. |
Links where to buy? |
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DPMSINC.COM is where I got mine. forthehunt.com if you want to try to get it a little cheaper on the auctions jtdistributing.com and about a billion other places like ADCO, CDNN, ect that I've never used but heard good stuff about. |
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Many more are here: cmmginc.secure-mall.com/shop/index.php?shop=1&cart=150412&cat=5& |
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