I can't speak for others' rifles, I built 4 rifles this year so far, each one gets tested with couple mags of Tulammo just to see how gas system functions=if it functions with lower powered ammo, it will probably never fail to cycle with 855 ammo.
I have had one failure out of probably 400 rounds so far, a failure to eject.
I prefer brass cased ammo for ability to reload--most ammo has went up about 20% this year. Tulammo is still $5 box at wal-mart.
It is coated with a polymer/shelac/varnish or something. I ran some thru a rifle with no gas tube to sight it in, and it wanted to stick in the chamber since it was not immediately ejected, but it was still able to be cycled out with the charging handle. I did not notice any residue or anything in the chamber when cleaning. It is also supposed to be non-corossive now, but I clean throughly anyway as it is dirty burning ammo.
for practice and testing I recommend it, also for stockpile, in case next administration decides to tax the hell out of ammo and ammo becomes 200% or more what it costs now.