Best ammo for 5.56 1/7 twist 16" barrel...emphasis on the 1/7 twist w/16" barrel?  Please include pro/cons for the weight of the round.

What do you want it for? Target shooting? Plinking? Matches? Self defense? SHTF? The answer may vary depending on intended use.

For self defense/SHTF and if cost is not an issue, the Black Hills 77 gr Nosler NATO pressure ammo would be hard to beat.

For matches, any of the various Federal, Hornady or Black Hills 68-77 gr Match ammo should work well.

For varmint hunting, any of the 50-55 gr JHP or polymer-tip bullets may be the ticket. Just check to see that they shoot well in the faster twist.

For hunting critters larger than coyotes (i.e. smaller deer) the Winchester 64 gr Powerpoint and Powerpoint Plus may be the best bet.

If penetrating barriers is the goal (i.e. you are a cop who's concerned about engaging folks in cars through glass and metal) the Federal Tactical 55 and 62 gr ammo may be the best choice. The regular Federal 55 gr Trophy Bonded Bear Claw available to civilians is basically the same load.  

For general purpose ammo, or buying in large quantities, quality M193/M855 may be the way to go.

So as you can see, the word "best" kinda depends on what you intend to use it for. Some .223 ammo may be great at one task and not be so great at another. So pick a load tailored to your specific needs.

-Charging Handle

Thanks alot for your detailed answer, charging handle...that covers it.  My intended use is plinking, small game hunting (hog, varmit, etc.) and target shooting.

For plinking and practice, you may like the PMC 55 gr FMJ. It isn't an extremely hot load, but it tends to be very accurate. For varmints, the Federal 55 gr BTHP has always served me well. Of course others will perform fine also.

-CH