Just got notice that my Omega is in. I plan on running it on both my 6.8 (16") and my 5.56 (18") and bought mounts for both to make it easy to switch. Other than making sure I have the 7.62 cap on it when I shoot the 6.8 , what other considerations do I need to take into account? I hear about 'over-gassed' but I'm not really sure what affect that has on the rifle or how to do anything about it. Gun is a RRA LAR-15 ATH, mid length gas system; the 6.8 upper is also RRA, carbine-length. Do I need to think about a different buffer or gas block?

An adjustable gas block will solve any gas problem you have. But you can still have gas coming out of the ejection port back into your face. Just wear some good glasses!

interesting question

I would shoot them first before spending money. They will be overgassed but some are worse than others. I have 2 that I don't feel much change in and then 1 fixed with a buffer and 2 others with an adjustable gas block. The heavier buffer and/or spring can fix the over gassing on the cycling side but does not change the amount of gas coming back. If you are getting more gas in the face than you want the adjustable gas block is the fix.

Agree, try shooting them first. I couldn't get one of my AR's to cycle shooting subs with my can. Tried my other lowers and had no problems, no adjustments needed.

Get a gas buster charging handle and it will keep gas and powder out of your face.

Yep, i run gas busters on my 6.8, blackout sbr and 556. They all have heavy springs and h2 buffers also.

So, these gas busters are something to think about. Who's or what brand have you found to work best?

https://m.youtube.com/watch?v=VQIK_tbiN5w

Or make your own easy enough.
I made three and they work fine although as others have said most of my AR 's there is no issues with gas bad enough to need a gas buster.