Re: Flutting LMT MRP barrel???
I know ADCO does this, check out threads on AR15 with plenty of pics of them. I personally don't think they are that heavy to warrant it.
You may also consider the re profile of the barrel instead if you need to drop weight. I think on the "Rifles, barrels, etc section of the AR forum, they have the weight reduction numbers, not as much as you think.(on the MRP)
Hope that helps.
I don't have personal experience on the fluting in regards to potential accuracy issues, strength loss/gain, etc. Plenty of knowledge here and test by barrel manufacturers on it though.