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Posted: 8/8/2011 1:41:25 AM EDT
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Throughout the long ordeal of putting together my 6.5, the last thing I expected was to have trouble with the A2 flash suppressor. I mean, every instruction thread/manual/video I've seen goes into enough depth to say, "install muzzle device" and ends it there. Some mention replacing the crush washer, some don't. Here's my deal. With the crush washer in place, the solid part of the Muzzle device that should be at 6 o'clock is at 1 o'clock. That seems (to me) to be excessive, and I'm not happy about my odds of getting it timed without tearing up a $325 barrel. I've looked around and searched the forum, but I guess I'm the only one having issues, at least based on the total lack of info I've found. Maybe I'm just that much of a goober  that what is obvious to everybody else has slipped past me.So, realistically, what is my next step? Will the crush washer give enough for me to get 110 degrees of turn out of it? Do I try and find some peel washers? Do I try to sand the crush washer down a bit? It's going onto a Liberty Stainless fluted barrel, if it makes a difference. Thanks. |
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I'm not sure how far the crush washer is meant to squeeze but my A2 has one behind it. If you don't feel comfortable, you can get a peel washer which will allow you to change the thickness by removing pieces instead of crushing.
You might also try filing the back of the crush washer down to get you closer so that it won't have to go far |
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110 degrees of rotation will be fine.
ETA Here is what the military says about installing the flash hider: Install compensator (16) on barrel assembly (8) using combination wrench (15). Tighten compensator hand tight and then tighten a minimum of 90 degrees but no more than 450 degrees to align center of middle slot (25) with post of front sight assembly (10). Tighten compensator to complete alignment with front sight post to top dead center (TDC). Do not over rotate. If compensator is turned backwards, the compensator will loosen, so procedure must be started again with a new recessed washer. |
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Quoted: 110 degrees of rotation will be fine. ETA Here is what the military says about installing the flash hider: Install compensator (16) on barrel assembly (8) using combination wrench (15). Tighten compensator hand tight and then tighten a minimum of 90 degrees but no more than 450 degrees to align center of middle slot (25) with post of front sight assembly (10). Tighten compensator to complete alignment with front sight post to top dead center (TDC). Do not over rotate. If compensator is turned backwards, the compensator will loosen, so procedure must be started again with a new recessed washer. Thanks, that is exactly what I was looking for! |
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How much torque are we talking about here? I clamped the barrel in a padded vice (smallish pivoting vice, admittedly) and can't keep it clamped down tight enough that it doesn't spin, and that's just with about 20 degrees of turn so far. I'm probably being paranoid, but I don't want to screw up either the barrel or the upper. just for a flash suppressor. Thanks. |
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Quoted:
How much torque are we talking about here? I clamped the barrel in a padded vice (smallish pivoting vice, admittedly) and can't keep it clamped down tight enough that it doesn't spin, and that's just with about 20 degrees of turn so far. I'm probably being paranoid, but I don't want to screw up either the barrel or the upper. just for a flash suppressor. Thanks. Try using some inner tube as "padding". If you're using barrel vise jaws, you can apply some RTV silicone to the jaws. |
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I follow the Brownells video. They state 90 degrees to no more than 460 degrees. Supposedly there is not torque setting for the FH with a crush washer. The torque setting stated above is for a peel washer.
Brownell Video I just build my 5th AR, and the FH was 350 degrees out. I cinched it down one time to perfect timing without an issue without a torque wrench.  Some people fart around with tighten, loosen, tighten, loosen, etc, etc - Whatever makes you comfortable.
Also, the video shows a superb device for holding your upper to do this procedure. |
| When a Crush washer dosent do it I will Grind the washer alittle till I get about 45 to 50 degrees from timed and then just reinstall .... I dont do this unless its after the third time I tighten the suppressor and it dosent look close to time.... I have on some that dont take a crush washer polish the back of the suppressor untill tight and then use lock tite on the threads......An Ak's moreso than AR's..... |
| When a Crush washer dosent do it I will Grind the washer alittle till I get about 45 to 50 degrees from timed and then just reinstall .... I dont do this unless its after the third time I tighten the suppressor and it dosent look close to time.... I have on some that dont take a crush washer polish the back of the suppressor untill tight and then use lock tite on the threads......An Ak's moreso than AR's..... |
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Quoted:
torque spec is 15-20 ft/lb This Quoted:
When a Crush washer dosent do it I will Grind the washer alittle till... Not this. 
The crush washer is a malleable metal which (assuming the flash-hider threading was timed at all from the factory) will squish down down withing the proper torque range to guarantee both a tight fit and no damage to the threads. I myself required around 300° of rotation but only around 17 ft-lbs of torque. |
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