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Posted: 6/16/2013 8:31:12 PM EDT
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Building my first AR upper and have heard some things about what to do w/ gas blocks...looking for advice...
1) On low profile gas blocks with the set screws that snug up against the barrel, do I need to do anything to ensure the gas block doesn't move, such as dimpling the barrel where the set screws make contact? 2) Do I need to stake the screws, whether on the clamp-on style gas block, or the kind mentioned in #1? 3) In general, which style of low profile gas block appears to be the best in terms of staying put and not moving around over time with lots of rounds put down range? Much thanks! |
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1. You will need to dimple the barrel for the set screws. Brownells has a jig for that. The dimples need to be on the exact opposite side of the barrel from the gas port, otherwise your gas port will not line up.
2. Staking the screws is unnecessary. You should use some high-temperature low-strength thread locker like Rocksett. Use just a little bit and you'll still be able to break it free if you want to. Use the same stuff on your muzzle threads. Just a drop or two, no more. 3. The best gas block for staying put is one that's taper pinned on. With a holding jig and a taper pin reamer you can install a taper pin in an existing low-profile gas block. It's a pain, especially if you don't have the right tools. Failing that, I have never had an issue with set screws coming loose. |
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Dimpling not needed, since the set screws will bite into the metal instead. Once you have found the correct index for the block on the barrel, then you can dimple if you want, which makes taking the block off and putting it back on to the old index a lot faster.
Red loctite on the set screws, this way if you need to remove them later, you can transfer heat to the set screws via an old Allen wrench and torch to break the loctite bond. Just make the ID of the block about .001" larger than the barrel OD as the gas port, use the back Allen set screw location to drill the gas passage above, and add another set screw location towards the front. If you dimple after you have the correct index, then even the two set screws will be enough to prevent the block from rotating even with a flip up front sight, and a strike to it. |
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