My question is: What is the lightest 30 degree synthetic bag out there.
All I care about is 30 degree rating and weight.
I did a pretty thorough search of synthetic bags last year and considered the Pounder Plus.
Marmot may say that the Pounder Plus is a 25F bag but independent tests give it a EN13537 rating of 36F.
You'll get more warmth for the weight with a Montbell UL Alpine Burrow bag #3. Most folks who have tried Montbell bags will attest that the ratings are accurate. This bag is no exception. I've brought this bag down to 23F while wearing a synthetic jacket. The weight of my size long is 2 lb.,1oz, .just under spec.
If you go this route, choose the regular size only if you are small. I'm 5'9", 150 lb. and the long size fits me much better.