The Famous Grouse wrote:Like every other rifle, yours will have a preference. I would try as many brands as possible before buying large quantities of bulk ammo. There is practcal of functional difference or advantage in 5.56 vs .223. Buy what you can get and test them all. Personally, the only 5.56 rifle I have actually prefers .223 ammo with a 50 grain varmint bullet.
Grouse

.223 rifles can have twist rates all over the place.
1:7 and 1:14 barrels will like different ammo