What is the real need for a Crush Washer Anyway?

[Tactical30]

Why is there a crush washer on every AR? Is just to line up the Flash hider/Muzzle brake?
Or does it serve a special purpose?

Not having a crush washer on your AR wont stop your M4 from firing!

I always wondered this.

 

[LoneWolfUSMC]

Re: What is the real need for a Crush Washer Anyway?

It's to index and retain the flash suppressor. Peel washers are also used instead and in some cases are more desireable. The weapon will function without them.

 

[patches]

Re: What is the real need for a Crush Washer Anywa

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body">It's to index and retain the flash suppressor. Peel washers are also used instead and in some cases are more desireable. The weapon will function without them. </div></div>

+1

Used to clock the flash hider, sometimes they are different thicknesses or multiple washers used.

 

[sobrbiker883]

Re: What is the real need for a Crush Washer Anywa

So that the threads don't have to be cut precisely timed on both the mass-produced barrels and the mass produced flash hiders.

 

[Mgordon]

Re: What is the real need for a Crush Washer Anywa

I just time the threads. It may take an extra 5 minutes, but that is how I do them. If they ever switched muzzle devices the timing would be off, but that is just how I do it.

I also time the barrel threads to the action so the curvature of the bore is pointing in the 12 o'clock position.

I'm just picky like that.

 

[TwoGun]

Re: What is the real need for a Crush Washer Anywa

How do you determine the curvature of the bore?

 

[Mgordon]

Re: What is the real need for a Crush Washer Anywa

Well, you will have to hang in here with me while I explain it.

When you are chambering a barrel, you want the chamber to concentric with the bore correct?? There is no way that that bore is a perfect straight hole through the barrel. So you can put a long stemmed indicator in the bore and check a few inches in, dial that in, the pull it out and check 1/4" in and indicate that in. You need to keep going back and fourth until the first couple inches are running .0001-.0000" run out. By the way, you have the barrel through the headstock with a spider holding the left side (muzzle end) of the barrel, and the right (chamber end) is in the 4 Jaw.

Once the chamber end is running true, you now move your indicators on the muzzle side. You stick them in the bore and rotate the barrel in the headstock. You watch your indicator and figure out which is the high side or which way the bore is curving. You then make a indicating mark on the barrel and on the 4 jaw. You then cut your barrel shank and thread it. You then time your threads so that the curvature of the bore is in the top dead center position.