OK, I know I'm gonna get flack about this.  I't been asked before, but........
Other than rust, is there any difference between a chrome lined vs a chrome moly barrel?  I've read that a moly barrel is more accurate.
I would really like a BCM SOCOM 14.5 upper, but cost always is an issue in the Obama era.  Any thoughts????  Suggestions???

Chrome-lined is more durable, easier to clean, and lasts longer.  The accuracy benefits of chrome-moly, if they are even real, are so small most shooters will never notice, especially on a carbine.

most dont need a clb, but need has little to do with it.
get what you want can afford it will suit you just fine.

Exactly when it comes to this subject.

The barrel is not really the place you want to go cheap. I've gotten chrome-lined for all the barrels I have bought, and it helps me to sleep better at night. Otherwise, I would just end up second guessing myself about whether I should have just ponied up for CL. YMMV

I have had great luck with both CL and non CL barrels. I always clean my weapons after range/training so I never really ever allowed the barrels to build up heaving fouling etc. Cleaning a non CL barrel was always easy for me. I also couldn't tell you which would be more accurate. I think a quality manufactured barrel, either CL or non CL would be more accurate than me anyway. Get whichever you can afford and have fun with it. Just make sure you get a quality barrel from a known manufacturer and keep it maintained.

To better answer your question we first need to make sure you understand what your asking....

To start with, generally speaking, most rifle barrels are made out of two materials...Chromium Molybdenum better known at ChromeMoly for short and stainless steel(410 or 416).   The only similarity between a ChromeMoly barrel and Chrome lined is that the ChromMoly barrels GET Chromed lined or do not.  Chromium Molybdenum is what steel the barrels are made from.  The Chrome lining is added after the barrel has been made and twist added.  Stainless steel barrels do not get Chrome linings.   So when you hear or see ChromMoly that has nothing to do with the barrel lining.  All it's basically saying is the barrel is not made of stainless steel.

With that said, Yes in the past an unlined ChromeMoly barrel was considered the more accurate of the two.  I think however in some circles of target grade shooters they still prefer non lined barrels.  Many of todays chrome lined and stainless steel barrels offer accuracy challenging non lined barrels.   While Chrome lining may offer a slight decrease in accuracy what it does give the barrel is much increased shooting life.  A non lined barrel may only have a life of say 3000 to 5000 rounds while a Chrome lined one may double or even triple that.  Depending on barrel maker and rounds fired.  For a combat type rifle a chrome lined or stainless steel barrel is the way to go due to ease of maintenance.  And has been mentioned the little less accuracy will probably not be noticed.

Just get it...other than being a little heavy (which is the whole idea) that upper is pretty hard to beat...$500 out the door!

My guess is the shift to leight weight and midlength barrels may result in discontinuation of the SOCOM profile (I think CMMG has already dropped it).

The Army's shift to all M4A1s and converting M4s to A1s may result in resurgence of the profile and a supply shortage/cost increase.

So get it.