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number1olddog
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Posted: 1/24/2010 12:07:41 PM

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I have a BCM mid upper with Midwest Industries free floating handguard. I took off the handguard and was looking at the gas block and noticed one set screw was flush (tightened) in the gas block and the other appeared not to be screwed in like the other. The screw that had been screwed in was obviously lock tighted as there was red seeping through. My question is does BCM only dimple one hole in the barrel to use with gas blocks or do they dimple both and just didn't screw in the other set screw? I emailed them about it yesterday and haven't received an email back yet.
rushca01
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Posted: 1/24/2010 12:19:36 PM
Quoted from Paul (BCM)

No, you will not need to add more dimples. Tighten (and loc-tite) all retaining screws on your gas blocks. But just the first retaining screw in counter sunk in a dimple.
BCM stripped barrels have one dimple. That dimple is to insure the securest fastening of the rear retaining screw. That first dimple is mil standard measurement. It exists in the same spot on every gas block or FSB made for the M16/M4. The reason is that the machining operation to drill the vertical hole for the gas port in the gas block, is also the same op to form the hold for the first retaining screw. (actually the same on a standard FSB) So it is a standard. After that a second retaining screw position will vary with every single gas block made. No more standard. Some gas blocks are the same because they copied others, but their is not a set position. A second dimple would require you to only pick from a sepecifc gas block/s.
You can throw a second dimple in for fun if you want, but its not needed.
briansmithwins
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Posted: 1/24/2010 1:40:59 PM
I'd stake the screws too. Loktite fails under heat and gas blocks get hot.

BSW
Si vis pacem, para bellum.