The crush washer is essentially a conical washer manufactured of 302 stainless steel. Like most pieces of steel, the bar from which these are made, may be in a variety of states, not least it may be cold rolled in its final form and as this steel type is a work hardening grade, it may too hard to fulfill its function even as manufactured. YHM crush washers are typically in the dead soft or normalized state as supplied and are among the best of these parts.
The washer orientation on the barrel results from the need to provide an even pressure on the back of the flash hider and hence hold it square, as far as is possible, on the muzzle threads. Originally the washer was fitted to deform against the shoulder of the barrel but this left the flash hider resting against the small diameter and more likely to be forced off axis, hence the orientation is important. One of my pet peaves is the use of 5/8-24 threads on barrels set for 0.750 gas blocks. The gas block diameter precludes the use of sufficient shoulder on the barrel behind the thread to correctly locate the washer edge. Blackout barrels requiring this thread pattern are problematic so a non indexing muzzle attachment is the best selection.
It is extremely difficult to deform a crush washer in a vice. For problematic combinations a barrel stub is the best solution. Noting the rotation required, the crush washer may be set on this "dummy" assembly and then transfered to the intended build for slight final tightening.
The original peel washers were laminated from stainless and phenolic. It was found is some instances that the phenolic would degrade between the shims and the flash hider would be left without tension and free to rotate.


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and torque that sucker down preferably in a barrel vise. 
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