A crush washer question


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fanchisimo
July 12, 2013, 10:15 AM
I'm am building a 6.8 upper to be my hunting rifle, and I have a question about the crush washer. When I slide the crush washer on the barrel and then thread on the A2 flash hider, it stops at the perfect 12 o' clock position, but it's only hand tight, so to put it on with some tension I'd have to spin it a full 360 degrees. Is this much turning with a crush washer acceptable?

Here's another possibility. When I put the crush washer on facing backwards, the flash hider threads to the 6 o' clock position, which would require only a half turn to get it into the 12 o' clock position.

My question is what is the solution to this? Will a full rotation with the crush washer the right way be harmful in any way or will turning the washer around so that it only needs a half turn be a better solution? Or is there something with which I'm unfamiliar?

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allaroundhunter
July 12, 2013, 10:19 AM
You need to add shim(s) behind the crush washer (and don't use the crush washer backwards).

fanchisimo
July 12, 2013, 10:24 AM
Would a regular shim from an auto parts store work, or is there a specialized shim for firearms?

wally
July 12, 2013, 11:43 AM
Get a peel washer and adjust the thickness to exactly what you need. Then you won't have to replace the crush washer if you someday decide to get a suppressor that mounts on the A2 flash hider.

Going through all that with my Gemtech Halo. Crush washers are near universal because they require near zero labor to get the indexing right.


Another option I'd offer is to file a bit off big surface of the crush washer to equal about half a turn -- about 0.002" would be about right for 1/2"x28 threads. That's not a lot use a flat file larger than the diameter of the washer and move the washer against the file, rotating the washer as you move it to keep it level.

45_auto
July 12, 2013, 02:47 PM
about 0.002" would be about right for 1/2"x28 threads.

I believe that you missed a decimal point there.

1 full thread at 28 TPI is .0357".

Half that would be .0179", just a little less than .02".

wally
July 12, 2013, 03:13 PM
Oops! 1/56 = 0.0178

fanchisimo
July 12, 2013, 04:29 PM
Delete

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