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Posted: 1/5/2006 5:45:16 AM EDT
I have a 16" Sabre middy and Samson 9" FF handguards. I still have the triangular HG cap in place, so it's easy to see any movement in relation to the barrel / Samson. If I grip the Samson and the flash hider I can get MAYBE 1/8" total play side-to-side. If I hold it by the receiver and try to move the Samson, I don't see any play. On the other hand it seems as though the movement is in the barrel. Am I simply seeing visual proof that FF'ing is a good thing or does this mean I might have an issue? Barrel nut not tight enough? I wonder because my "groups" suck and that's not something I'm use to. Maybe the trigger just needs more breaking in...has a high spot on the tip of the hammer that's slowly polishing itself out against the carrier.
Link Posted: 1/5/2006 5:52:59 AM EDT
1/8" play at 16" translates into about 28.125" of play at 100 yards. 1/8" play at 9" (end of the handguard) becomes 50" of play at 100 yards. Assuming that the barrel is moving relative to the receiver (which it souns like), there's probably something seriously wrong. Sounds like the barrel nut isn't tight enough to keep the barrel in place against the upper receiver.

Note: I'm not an expert. That advice may be bad. No warranty expressed or implied...
Link Posted: 1/5/2006 5:59:12 AM EDT

Originally Posted By JackalAR:
Barrel nut not tight enough?

Pull the handguards off and check to see if your barrel nut is loose.

Link Posted: 1/5/2006 6:03:37 AM EDT

Originally Posted By Stickman:

Originally Posted By JackalAR:
Barrel nut not tight enough?

Pull the handguards off and check to see if your barrel nut is loose.

+1. If your barrel nut is loose you will need to pull the gas tube to (re)tighten the barrel nut. Did you assemble the upper or did it come from the manufacturer that way? MJD
Link Posted: 1/5/2006 7:58:15 AM EDT
When are you observing the play? Is it while you are shooting, or are you physically moving the barrel with your hands?

If you are flexing the barrel with your hands, as long as the barrel nut is tight, I wouldn't worry about the movement.

I would make sure the handguard cap isn't interfering with the Samson handguards, if it is, this may cause accuracy problems
Link Posted: 1/5/2006 8:01:06 AM EDT
I had the barrel nut tightened down for me by a local shop because they had the vise block and armorer's wrench. I brought along a torque wrench but they didn't use it so I assume it got tightened down enough or better. He said it's suppose to be at about 30 ft/lbs then go the the next slot the gas tube will pass though. I know they used moly grease too. I think it's just barrel flex and the fact that the Samson just clamps around the barrel nut. It's maybe 1/16" each way...so 1/8" total or less. I know the barrel feedramps came pretty flush with the end of the receiver there in the magwell, but it was just a hair shy so I had to knock that edge off (the receiver) with a needle file. I'll try again tonight to move the barrel by just holding the receiver...if it's still as bad as when gripping it by the Samson, I'll look further into it. Thanks guys.
Link Posted: 1/5/2006 8:04:31 AM EDT
It's only when I grip the very end of the FH and torque on it against the HG's. I noticed this while adjusting the Samson...used the HG cap for center refrence. It NEVER makes contact with the HG cap...there's room for about two - three sheets of paper between them.
Link Posted: 1/21/2006 4:22:28 PM EDT
Well, when I grip it by the receiver and push / pull side-to-side from the FH, you can see the barrel moves MAYBE 1/16" total where the handguard cap and FF rail "meet". You have to be wrenchin on it pretty good though. Does this sound like normal barrel flex in a CMV barrel?
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