Strange that you should particularly mention the A7 Ranger ( I think you meant to say 85 though) because one of my fellow rifle club members was showing us the crown of his A7 rifle that he bought only last September so less than a year old. The muzzle crown was badly eroded all over but especially on one side and looked similar to the result of holding the end of a plastic garden hose over a candle. He said that this was the result of leaving the moderator on the rifle and storing it in the cabinet (traditional manner butt down) for only two weeks. I simply couldn't believe the extent of the damage in such a short length of time and had to call over several other club members to see it, all were equally shocked. I now wish that I had taken a photograph of the damage.
My fellow club member took the rifle to a reputable gunsmith the next week hoping that the barrel could be saved by cutting it back and rethreading but unfortunately the bore scope showed that the damage extended a fair way down the one side of the bore. So now he is looking at re-barreling a rifle that is less than a year old.
Incidentally he did test fire the rifle on the off chance that the damage wouldn't affect accuracy too much but the results weren't exactly hopeful with patterns rather than groups being produced.
It seems like the products of combustion combined with condensed moisture in the moderator produces a pretty corrosive substance.
Personally I'm old school and usually clean after shooting but I have been known to leave it a week if I know I will be using the rifle again during the week. Moderators always stored off the rifle and rifles stored muzzle down in the cabinet.