With my FFL finally getting in contact with MWC, I am going to have a lower receiver in my possesion before long.  I have all the parts for a complete lower assembly, but I lack an upper.  I want one that is already assembled - no screwing with barrel nuts for me.  It looks like I am going with a 16" barrel, and so the question:  What are the pros and cons of the three main barrel profiles?  By three, of course I mean 'Heavy,' 'Lightweight,' and 'M4' profiles. 

Heavy is... heavy, so is there any good reason to go with it?  Accuracy?  My area does not have long shot possibilities.  Is there a downside to the pencil profiles?  And finally, if I don't have a grenade launcher, is there any good reason to go with the M4 profile? 

Thanks a lot.



Kaso

Another question: will this be a free-floated barrel? If yes, you can go a little lighter, because different pressure placed on the handguard from hand position, slinging up, etc, will not influence POI. if it is not a FF barrel, you may want to go with a medium contour, as opposed to light.

Finally: will you be hanging a can on the end of the barrel? If so, it may be advantageous to go with something heavier than a pencil barrel. I imagine that a long thin barrel + heavy can will lead to larger POI shifts when you dismount the can, but that's a guess.

Also, the M4 profile is pure aesthetics, unless you own an M203. In many ways, it is the worst of all possible worlds. The barrel is almost a pencil barrel under the handguards, then gets thicker out where it is exposed at the end. This means that you have most of the drawbacks of a heavy barrel (nose-heavy feel, since the weight is way out front) and fewer of the benefits (it is less rigid where it needs to be). Unless you have a grenade- I mean, flare- launcher, or just like the look, skip the M4.

Mike