I had a local smith perm attach a Surefire FH556 212. He said that he used hi temp silver solder to do the job.
Has anyone else used this method to attach their flash hiders? His solder job looks a little too clean ( no discoloration on barrel or flash hider).
if under 16 inches you need the FH to be Pinned! solder will not hold up to what the ATF will do to hit you with a Short barrel rifle violation they will heat it ,put a Pipe wrench on it .they will get it off .
I had My Colt Pinned By ADCO you can not get it off without destroying the FH .
it is better to be safe than sorry
Put the barrel in some barrel vise blocks wrapped in a piece of rough leather. Try to remove it with a wrench, if it turns you have your answer.
It’s always best to blind pin and weld it. But some shops still use the silver solder method.
Two pics. One is my pinned BCM the other is my silver soldered Noveske.
Warpig, silver solder is accepted by the ATF as a method to perm attach, however, it has to be the 1100 degree stuff. My understanding is that it is generally messy. Maybe I’m just being paranoid.
As above.
ATF accepted methods. Pick any one:
Silver solder with a melt point of 1200F or higher.
Welded over blind pin
4 equadistant direct welds on seam between muzzle device and barrel
didn’t know that thanks for letting me Know i stand corrected 
By saying “the job looks too clean” will always have doubters even if it was done correctly.
I always go with welded pins and have them show so there are no questions.
I like welded pins as well which is why I asked for that to be done. When I went to pick up the upper this is what I got back. At any rate, today I went to another smith (for a second opinion) and he said that that it was good to go.
Welded pin to be safe
I prefer the pin and weld method too.
I missed the picture the first time through. It appears he didn’t use the shims. The gap and solder looks like crap.
How do you think it is possible to sweat the soldier in after your muzzle device has been timed and torqued? The silver solder MYTH has been regurgitated ad nauseam. Heating your barrel and muzzle device anywhere near 1200 degrees is going to draw back or increase the hardness and create short term problems. The Surefire muzzle devices flash cut fairly quickly to begin with.
That looks like he pinned it and welded over it.
Just as an FYI, “silver solder” is actually brazing. This may explain some inconsistencies in responses people have received from the ATF with regards to soldering.