I can’t comment on a specific AR-10 platform. What I can tell you is that I think the best general practice is to get it right from the start. It’s well worth the wait and/or money to go with a proven design.
From what I understand LaRue is not even giving a timeframe. So a known 12+mo wait may be better than an unknown one?
I really want an 18" OBR 762 and am trying to save up for one, but with the wait, I may as well order it and by the time it’s ready, I’ll have the money saved lol.
If I begin looking for a LMT MWS, should I be looking at the 16 inch barrel or the 20 inch barrel?
I understand the difference the 20 inch barrel will make on velocity. Will it have any effect on accuracy? Initially I won’t be shooting over 500-600 yards but I would like to have the capability to further where the velocity would have a positive impact.
At 500 to 600 yards the 16 inch should be satisfactory. If you are looking for precision and greater distance I would consider the steel barrels in 18 or 20 inch (http://www.lmtstore.com/bolts-carriers-groups.html?p=5). Buy what is available and swap the barrel later if you want - modular is a good thing.
I am pleased with 16 inch with a WC muzzle brake - minimal felt recoil. Accurate.
There is a lot less difference in velocity between a 16" and 20" .308/7.62 than most people assume.
Really, the difference between two has pushed me toward the opinion that if you need a 20" barrel to do what you need doing, then you probably need to step up into the .300 WinMag/.338 LapMag area anyway.
Actually a longer barrel affect accuracy when the rigidity of the barrel drops. So in effect a longer barrel might actually be less accurate if it is thinner, or that is how I understand what’s been studied in the past. If you look at the massiveness of the LMT barrels, long or short will make no difference due to the large diameter of the barrel. I understand the stainless barrel is more accurate, but you pay a lot more for it. If you can get one in any barrel length go for it.