03-23-2023, 02:27 AM
GF, I've heard that a final torque adds about .002.
I'm leaning toward shims for these reasons:
1) Though crush washers give ease of timing — within their limits — I don't like the amount of torque required for a crush washer relative to the degrees of rotation you get. I was cranking like hell on my prototype UltraSlim washers just to get 90°. It seems crush washers are a down and dirty way for military armorers to mass install timed A2 muzzle devices when the accuracy standard is 2-4 MOA. Many claim crush washers do not crush evenly and thus can introduce cant to the installed muzzle device. This could lead to accuracy degradation if the walls of the device are not acting evenly on the expanding gas, and, worse, to baffle strikes if the angle of cant and the length of the device create the perfect storm. Anyway, it's a different set of parameters for the civilian home builder who has more time and more stringent accuracy expectations.
2) I feel the thickness of crush washers and jam nuts subtracts too much from the available muzzle threading, leading to less and less thread engagement. Typical 5/8-24 muzzle threads are .625 or so long, and subtracting a standard crush washer thickness of .150 leaves .475 thread engagement. We put premium 3A male threads on our barrels and 3B female threads on our muzzle devices, so good engagement is important to me. I feel that the microscopic "rattling" of a "loose" muzzle device is detrimental to accuracy.
3) I've calculated it and with not more than a max of three shims mixed and matched from a kit with four shim sizess — .002, .003, .007, .015 — one can get 180° rotation with a linear travel of .021 in .001 increments. Any fudging can be done by slightly more or less torque effort. It's amazing to me how much rotation one gets for how little thickness per shim. This allows almost exact alignment and timing while retaining maximum thread engagement. I think shims are mostly reusable; one can always add or replace a .002 shim if one feels a shim has been crushed too much. But they're flat washers, so there's not any flex to really crush.
Personally, I don't bother timing my three-prong Alpha and closed three-prong Bravo devices, but I might if I have a shim set — and I certainly plan on aligning my Delta muzzle brake with its four ports at 3 and 9 o'clock.
I'm leaning toward shims for these reasons:
1) Though crush washers give ease of timing — within their limits — I don't like the amount of torque required for a crush washer relative to the degrees of rotation you get. I was cranking like hell on my prototype UltraSlim washers just to get 90°. It seems crush washers are a down and dirty way for military armorers to mass install timed A2 muzzle devices when the accuracy standard is 2-4 MOA. Many claim crush washers do not crush evenly and thus can introduce cant to the installed muzzle device. This could lead to accuracy degradation if the walls of the device are not acting evenly on the expanding gas, and, worse, to baffle strikes if the angle of cant and the length of the device create the perfect storm. Anyway, it's a different set of parameters for the civilian home builder who has more time and more stringent accuracy expectations.
2) I feel the thickness of crush washers and jam nuts subtracts too much from the available muzzle threading, leading to less and less thread engagement. Typical 5/8-24 muzzle threads are .625 or so long, and subtracting a standard crush washer thickness of .150 leaves .475 thread engagement. We put premium 3A male threads on our barrels and 3B female threads on our muzzle devices, so good engagement is important to me. I feel that the microscopic "rattling" of a "loose" muzzle device is detrimental to accuracy.
3) I've calculated it and with not more than a max of three shims mixed and matched from a kit with four shim sizess — .002, .003, .007, .015 — one can get 180° rotation with a linear travel of .021 in .001 increments. Any fudging can be done by slightly more or less torque effort. It's amazing to me how much rotation one gets for how little thickness per shim. This allows almost exact alignment and timing while retaining maximum thread engagement. I think shims are mostly reusable; one can always add or replace a .002 shim if one feels a shim has been crushed too much. But they're flat washers, so there's not any flex to really crush.
Personally, I don't bother timing my three-prong Alpha and closed three-prong Bravo devices, but I might if I have a shim set — and I certainly plan on aligning my Delta muzzle brake with its four ports at 3 and 9 o'clock.
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