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Old December 3, 2010, 07:18 PM   #1
WhyteP38
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AR-15 Flash Hider Problems - Help Needed

This is my first time installing a flash hider, and I have run into some problems.

I am installing an A2 hider with crush washer onto a Bushmaster 16" superlight barrel. I also have the aluminum vise blocks.

I put a strip of rubber (piece of bicycle tire tube) over the barrel to protect from marks from the blocks. After tightening the blocks, I went to tighten the hider. After about 50-60 foot pounds of torque (guessing), the barrel shifted. So I redid everything and tried again. Same results. Tried twice more for a total of 4 times. Same results each time. The washer doesn't appear to have crushed at all.

So I removed the rubber, thinking the blocks needed better grip through actual contact with the barrel. Same result.

Now I have two silver stripes down the sides of the barrel.

Just how tight should I tighten everything in the vise?

And are those silver stripes aluminum or bare barrel steel? After wiping the barrel down with a little CorrosionX, it looks like the parkerizing is gone where those stripes are. But maybe I'm mistaken.

Any help would be great. I'm also thinking I've got a crush washer that won't crush.
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Old December 3, 2010, 09:03 PM   #2
DnPRK
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Pre-crush the washer a little in the vice jaws. Also, the crush washer narrow end goes towards the barrel shoulder and big end towards the flash hider.
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Old December 3, 2010, 11:25 PM   #3
WhyteP38
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Excellent idea on pre-crushing the washer!
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Old December 4, 2010, 03:41 AM   #4
HiBC
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Remember the muzzle is the last goodbye to the bullet and is critical to accuracy.Distorting it is not helpful.I don't use the thick spring washers.Some use sparkplug washers.Some figure out the optimum thickness to index the pickle and order a ground,hardened .500 id shim washer from MSC or McMaster.I index mine by counterboring the rear of the pickle the correct amount to index.I don't use a washer. I would guess my two white knuckle torque at about 20 ft lbs.
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Old December 4, 2010, 07:58 AM   #5
digdeep74
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too tight

Here are the proper tourqe values for several parts on your ar15 ,the problem is you are tourqing your flash hider above the tourqe of your barrel nut.


Torque Values:
Compensator (Flash Suppressor) - 15 to 20 Ft. Lbs.

Barrel Nut - 30 Ft. lbs. Minimum, not to exceed 80 Ft. Lbs. to align the next slot in the barrel nut.

Carrier Key Screws - 35 INCH pounds to 40 INCH pounds.

Lower Receiver Extension (Buffer Tube)
Rifle - 35 to 39 Ft. Lbs.
Carbine - Tighten the locking nut to 40 INCH pounds plus or minus 2 INCH pounds.
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Old December 4, 2010, 02:01 PM   #6
Scorch
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Quote:
After about 50-60 foot pounds of torque (guessing)
Guessing????? How about a torque wrench? Besides, 1/2-20 threads don't need that much torque.

If the bottom of the bird cage is not contacting the washer, the threaded portion of the barrel may be bottoming out inside the bird cage.
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Old December 4, 2010, 02:11 PM   #7
WhyteP38
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Quote:
Guessing????? How about a torque wrench? Besides, 1/2-20 threads don't need that much torque.

If the bottom of the bird cage is not contacting the washer, the threaded portion of the barrel may be bottoming out inside the bird cage.
Guessing because I was not expecting this problem. Having worked on car engines before, I have a pretty good idea of torque values. Also, I checked the fit prior to my installation attempt, and everything was fine.

I gave it a little more torque than I anticipated to see if the washer would crush, but I stopped at about 50 foot pounds because that was as far as I wanted to go.

I have since tried to pre-crush the washer by itself, but it won't crush at all. Since I plan to toss the washer, I ended up really laying into it. Not the slightest bit of crush.

At this point, I'm thinking about using a different crush washer and/or peel washers. If anyone has some spare they'd like to sell, please PM me.

Thanks.
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Old December 4, 2010, 03:09 PM   #8
guncrank
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I use paper to line AR vise blocks not rubber.
The flash hider should just thread easy
Do you have excess to a .5-28 die?
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Old December 6, 2010, 06:14 PM   #9
WhyteP38
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Thanks, everyone, for your suggestions. The group-mind is a powerful thing and got me thinking "outside the box."

I ended up using HiBC's idea of sparkplug washers. It took two of them (with the indestructo washer sandwiched in between) to align everything properly, and then it all went together very smoothly.

Since the sparkplug washers are steel, I used some Birchwood Casey Perma Blue to blue them.

For some reason, stores in my area don't carry sparkplug washers by themselves, so I had to get two lawnmower sparkplugs just to get the washers. But everything is together now, and it doesn't look bad.

Last edited by WhyteP38; December 6, 2010 at 06:19 PM. Reason: Spelign
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