by *krink* I assume you mean the AK-74U style expansion chamber? If so, it really serves only one purpose, that of an expansion chamber to improve the reability of short barreled rifle -- in the case of the AR, it is no use whatsoever on anything that does not suffer from a short dwell problem.
A sound suppressor is in itself an expansion chamber and increases the back pressure even more than the *krink* style expansion chambers... often to the point of being too much, but then I see a lot of people putting expansion chambers of barrels that I quarentee all they are doing is making the timing worse... but it looks cool.
You give no idea of what the base rifle is, so answering your question is very tough... but if you want some sort of combination expansion chamber/sound suppressor, the original moderators from the XM177E2 is not bad (carbons up sort of fast) -- of course the short, purpose built modern moderators are far better.