http://thecmp.org/2016-cmp-rifle-and-pistol-rule-changes/2016 restrictions will simply require M16/AR15-type rifles that:
•Are chambered for the 5.56 x 45 mm (.223) NATO cartridge.
•Are designed or modified for semi-automatic fire only.
•Have either a gas-impingement system or a
piston-operated gas system.
•Have a barrel that is no longer than 20 inches, with or without a flash suppressor (16” barrels are permitted).
•Use one upper receiver and barrel for the entire match.
•Have a trigger pull of at least 4.5 pounds.
•Use standard service magazines or commercial equivalents that do not contain added weights.
•Have a fixed or collapsible butt-stock that may vary in length and even be adjusted between firing stages. Butt-plates or cheek-pieces may not, however, be adjustable.
•Have a standard A1 or A2 pistol grip.
so bring all your M4geries and everything in between