At this time, the only company(that I know about) which makes  a currently-available quick change barrel system that will change calibers is MGI, and the product is called the QCB . It uses normal AR15 barrels, and no expensive proprietary barrels are needed with this system. It changes barrels in under 30 seconds, and returns to zero very well, and is capable of sub-MOA accuracy. It is also the least expensive barrel changing system for the AR15 on the market. It has been on the market for over 2 years, has a great track record, is now part of a fully modular system coming out from MGI.

I am the Factory Rep for MGI on ARFcom, and would be happy to answer any questions you may have, either on the forum here, or by phone or email.

My contact info is in my sig line below.

Please correct me if I'm wrong, but I'm under the impression that LMT offers only 5.56 barrel options in proprietary configurations at this time to the civilian market.

Perhaps this might change in the future, or after S.H.O.T.