You're question's pretty vague...
What are you looking for? In a 1/7 CL M4 gov't profile (light under the handguards) CMMG is an option, IIRC, Bushmaster may have them, but don't quote me on that, Colt, LMT, those are your major, "mainstream" options. There are also others that are not quite as well known that are out there, like BCM, and many of them are quality as well. However, just from experience, people looking for 14.5" M4 barrels are more concerned with practical accuracy than pinpoint accuracy, if they wanted anything more, there are plenty more accurate barrel profiles and types out there.
Is that what you're looking for? Or do you mean something else by "M4 Lightweight 14.5?"
Are you looking for a whole upper, or just a barrel?
The CMMG will be a quality barrel, but any of the above will.
For plinking, you're almost going to be entirely limited to 55gr. as that's what's found most often available and cheaply. 55gr. will work just fine in the 1/7 twist, though it's supposed to be for heavier bullets. Furthermore, 62gr. and up are available, but are usually more expensive than 55gr. ball, as 55gr. is the most produced, and most reloaded weight. Under those circumstances, whether you have a 1/9 or 1/7 barrel is almost irrelevant, given the overlap of what they will shoot accurately. Again, if you want to do more than plinking, it may be more important to you, but for plinking, it's really just preference.
HTH,
~Augee