Suppressors 350 legend through a 30 cal omega can?

It might work once....

.355" is a lot bigger than .308", even with your overbore clearance in cans.

An existing .308 can will not work safely with a .355" projectile.

Additionally, a can bored for 9mm will not work well with a .308 rifle since it will be overbore to the extent that it won't suppress much of the sound.
 
It might work once....

.355" is a lot bigger than .308", even with your overbore clearance in cans.

An existing .308 can will not work safely with a .355" projectile.

Additionally, a can bored for 9mm will not work well with a .308 rifle since it will be overbore to the extent that it won't suppress much of the sound.
I agree with your first statement.

second not so much.

It is very common to shoot .223 through a .308 suppressor which is a difference of .085 vs a difference of .047 for .355 (9mm).
I'll never buy a dedicated .223 can again.

Silencerco Hybrid: which can take anything from .223 to 45-70 (bored for .460 projectile) shows that .223 is 6db quieter than .308