Neither, a third suggestion instead -- first some points to consider.
1. Sounds from your description that the prototypes are basically "MIM" ie, metal injected, a term I'm using to differentiate from a sheet metal, cut out and stamped or whatever shim. If it's not from a continuous sheet then the metal-grain boundaries won't be as strong or aligned as from a sheet. So I'm not sure you can bank on torque consistency or consistent behavior under torque/presssure... which means each shim can behave differently from the others.
2. Crush washers do apply uneven torques to the barrel and the muzzle device because they don't crush evenly all the way around, some parts stick out more than others, or contort a bit more than others, etc.
3. The REAL way, IMO, is to develop a rather thin, knurled jam nut. And either forget about sliding the gas block on after (ie, the knurl should be slightly larger diameter than the barrel, so the grip device will not scratch the barrel when you grab the jam nut), or else allow for some gap for the pliers... I don't know if you can make a strong enough 5/8-24 hex sided jam nut that is a max of .750 (assumed diameter of your barrel), this would be from vertex to vertex not flat to flat dimension... so that it's less than barrel diameter/gas block sliding.
I think the muzzle device should always go on after the barrel is set with gas block (and gas tube). Using a jam nut will allow you to change it at will, and also to take off easily for gas block work if desired. ps, there are some "thin blade" crescent wrenches that can help for those tight dimensions between device and jam nut also. I have one for the hex style jams.
Torquing of jam nut/muzzle device imo is not as critical as with a shim. slightly more than hand tight works b/c after a few shots, the carbon buildup will further inhibit it from turning.
Most fancier "non-tuning" muzzle devices are including a slip-type jam nut style "extension" (re, Fat Bas**rd latest version) on the rear of their device... which would be kind of $$$ to develop. You can get jam nuts from amazon for a few dollars each.
I use jam nuts almost exclusively, and am not going "to war" so torquing, per se, is not a spec I need.
Further note: I also use a bit of anti seize on threads/devices before installing, again to allow for removal without fear of galling.
Since this has a lot more detail than most opinions, I'll say "my $0.10" vice "$0.02" -- LOL!!!
OK, here's another idea that will help folks in tuning... can you make a small "match mark" line at Top dead center on both the barrel tip and your muzzle pieces... (muzzle piece might be harder if they are symmetrical, as in you can "time" it in any of 3 or six different alignments... ). At least tdc on the barrel, at the end of barrel and right before the threading so it's available to observe while tightening down. Even if it's a white or black "paint" mark instead of an etched groove...
1. Sounds from your description that the prototypes are basically "MIM" ie, metal injected, a term I'm using to differentiate from a sheet metal, cut out and stamped or whatever shim. If it's not from a continuous sheet then the metal-grain boundaries won't be as strong or aligned as from a sheet. So I'm not sure you can bank on torque consistency or consistent behavior under torque/presssure... which means each shim can behave differently from the others.
2. Crush washers do apply uneven torques to the barrel and the muzzle device because they don't crush evenly all the way around, some parts stick out more than others, or contort a bit more than others, etc.
3. The REAL way, IMO, is to develop a rather thin, knurled jam nut. And either forget about sliding the gas block on after (ie, the knurl should be slightly larger diameter than the barrel, so the grip device will not scratch the barrel when you grab the jam nut), or else allow for some gap for the pliers... I don't know if you can make a strong enough 5/8-24 hex sided jam nut that is a max of .750 (assumed diameter of your barrel), this would be from vertex to vertex not flat to flat dimension... so that it's less than barrel diameter/gas block sliding.
I think the muzzle device should always go on after the barrel is set with gas block (and gas tube). Using a jam nut will allow you to change it at will, and also to take off easily for gas block work if desired. ps, there are some "thin blade" crescent wrenches that can help for those tight dimensions between device and jam nut also. I have one for the hex style jams.
Torquing of jam nut/muzzle device imo is not as critical as with a shim. slightly more than hand tight works b/c after a few shots, the carbon buildup will further inhibit it from turning.
Most fancier "non-tuning" muzzle devices are including a slip-type jam nut style "extension" (re, Fat Bas**rd latest version) on the rear of their device... which would be kind of $$$ to develop. You can get jam nuts from amazon for a few dollars each.
I use jam nuts almost exclusively, and am not going "to war" so torquing, per se, is not a spec I need.
Further note: I also use a bit of anti seize on threads/devices before installing, again to allow for removal without fear of galling.
Since this has a lot more detail than most opinions, I'll say "my $0.10" vice "$0.02" -- LOL!!!
OK, here's another idea that will help folks in tuning... can you make a small "match mark" line at Top dead center on both the barrel tip and your muzzle pieces... (muzzle piece might be harder if they are symmetrical, as in you can "time" it in any of 3 or six different alignments... ). At least tdc on the barrel, at the end of barrel and right before the threading so it's available to observe while tightening down. Even if it's a white or black "paint" mark instead of an etched groove...