As a word of caution, I've had two crush washer failures over the last month. I have been exclusively using Aero Precisions's VG6 Gamma and Epsilon muzzle devices, both of which include crush washers. On two recent builds using the Epsilon versions (one black and the other a bead-blasted stainless steel), the crush washers had no elastic deformation and, instead, brittle fractured. In both cases, I was trying to properly time the muzzle device when one failed at under one half of a complete rotation and the other probably closer to a three-quarter rotation. In both cases, I could tell the washer was not crushing as the amount of force/torque needed to rotate was excessive. Normally, once the initial elastic deformation starts, the effort drops slightly. In both cases, a loud pop occurred, and the fractured crush washer pieces fell to the floor. I notified Aero Precision and they were kind enough to send me four new crush washers, and they stated that they would pull a sample batch to test. Just be careful - nothing like hearing a loud pop on a brand new build when you know something gave way while you were completing an "angle of turn" torquing method. In my case, no harm, no foul, but that sudden slip of torque could have caused me to damage some other rifle part (or myself).
Luckily, I had a few spares to complete the latest build, which just happened to be a new 20-inch .224 Valkyrie on a Mega Arms billet lower, upper, handguard, trigger, with Spikes Enhanced LPK and MFT Minimalist stock.
Luckily, I had a few spares to complete the latest build, which just happened to be a new 20-inch .224 Valkyrie on a Mega Arms billet lower, upper, handguard, trigger, with Spikes Enhanced LPK and MFT Minimalist stock.