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Posted: 6/6/2005 7:37:06 AM EDT
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I have a YHM four-rail forearm mounted on my AR. Every time the barrel gets warm, the forearm loosens up. Blue loctite did not help, and this happened even after I torqued the "jam nut" to 50 ft-lbs! I am trying to think of a way to index the forearm tube to the upper or lower without messing with the barrel nut. Does anyone know of a fix? |
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Ahhh, when I first read you post I was thinking of the two piece handguards, not the free-float tube. I should have read more closely. You could try staking the rail to the nut. As for indexing to the upper, you can always use a mount or riser rail that spans the gap between the upper and the foreend. YHM makes a few different sizes of extended rails that will work for this. |
| FWIW, I had the same problem with a YHM FF tube. Nothing I did, short of mechanical destructive means like staking, would keep it tight. At that point, I quit using YHM tubes. I know people who have had better luck. I didn't and didn't want the hassle, thus my choice. YMMV. |
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Thanks for the info. I contacted YHM; they think it's my fault and don't offer any solution. I asked them "What ever happened to 'good old Yankee ingenuity'?" I want to avoid modifying the barrel nut if I can, and any solution I come up with needs to be workable even if I install a different barrel (where the barrel nut might fit differently). I was thinking about taking a YHM-style barrel nut tool and cutting off the handle, then grinding it down until it fits inside the FF tube, then indexing the tube to it with a set-screw. It's a bunch of work with a grinder, but reusable and non-destructive. A section of barrel nut (with maybe 5 or 7 holes) would be perfect. I might go with a lifter rail. Wait! I'm stupid! All I need are three short pieces of gas tube welded together! Thanks again. |
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Even simpler! I got a 12" piece of #6 bare copper wire (#5 would be perfect if you can find some). I bent it into a sharp hairpin, with about 1 wire diameter between the legs. I cut the legs so the the hairpin was the same length as the barrel nut. Then I spread the legs just a little and slid the hairpin into two holes of the barrel nut, with one empty hole between the legs, at the bottom side of the barrel (opposite from the gas tube). I slid the hairpin in and then got it into final position with a few light taps from a sledge hammer. Then I tapped a hole in the forearm, screwed it on, and sank a setscrew into the small copper loop left exposed. Works like a champ, removable, and no damage to the barrel nut. |
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