Posted: 6/23/2011 5:28:35 AM EDT
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Hey guys, I'm putting a LaRue 11" rail on an SBR with a 10.5" bbl. The rail is one with the extended rail on top so that it actually sticks out a little past the end of the bbl threads. The issue I'm having is the proper order of installation. Following your instructions, the rail should be assembled in full before FSB (in my case a LaRue gas block), gas tube and brake are installed. But with the rail installed, how can I access the set screws of the gas block? How can I tighten the brake without clamping the barrel? (I'm using an AAC non-mount brake, with a crush washer). I'm afraid to apply the torque needed to use the crush washer with the upper in a vise. Really kinda confused on this and need help. This is my rail: http://stores.homestead.com/Laruetactical/Detail.bok?no=89 |
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Here's the best I can figure: Follow the installation instructions up to the point where I slip the rail over the barrel, but don't tighten (or even start to thread) the handguard nut yet. With the rail loose on the bbl, insert the gas block from the end and the gas tube through the upper (is that even possible?). Pin the gas tube to the gas block using a punch and pin through the holes in the rail (man, that will be fun). Then set-screw the gas block in place, again using the holes in the rail which is still loose so I can move it around to access each screw. THEN thread and tighten the handguard nut, locktite and insert the screws through the back side of the "keeper" THEN install the brake...but how can I get the brake safely tight without damaging the upper via torque? That's where I am with it... |
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If I remember correctly, your supposed to put the barrel nut and the locking thing on the barrel and tighten it down. The outer ring of the barrel nut will still spin allowing you to later put the rail on. Get your gas tube and block completely installed and locked down. Then slip the rail over the GB and tighten the rail down. You shouldn't be tightening the GB down after you installed the rail.
link After step three, the gas block should be completely installed and then go to step four where you slip the rail over the GB and install |
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Thank you Jon but that's a no-go. See the spacer in step 4? The hole in the top needs to have the gas tube run through it, and it won't fit over the gas block. So at very least the spacer needs to be on before the gas tube and block. Maybe that's the key, though? Put on just the spacer and not the rail? That would differ from the written instructions so I haven't tried it. |
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Link to video
You can do everything except install the rail itself when using the gas block. Whether your bbl is shorter than the rail is irrelevant. Everyone who has installed a rail longer than their gas block has gone through the same procedures. As you mentioned above, you can "hold" the key in place with the gas tube. It doesn't need to be attached to anything at that point in the install process. 
Edit: I just re-read your above comment. Yes, indeed put the key or spacer onto the gas tube prior to installing the gas tube/block combination. Slide the gas tube/block, and key/spacer onto the barrel/into the uppper, and tighten your set screws. |
