WELL,,, let me put it this way; just after I bought my bushmaster, I shot it using a couple boxes of winchester white box ammo. I used the stock open sights. I then removed the handle, put a 1" riser on it and scoped it with a 3X9 variable. Another trip to the range, with the same white box 55 grain winchester FMJ ammo showed me a 2.5 to 3.5 inch group(@100yds), from a solid rest! Phooey, did I get a lemmon??? I switched to Remington yellow box, 55 FMJ, darn near the same result! Didn't try the Federal Am. eagle type.
Since I already had dies for my .223 contender, I assembled some loads using Hornady 60 gr. V-max bullets. I loaded them at .5 grain increments up to max using WC-844 surplus powder,( this powder uses H-335 load data). Viloa! At a max of 24.0 grains, I got an even 1 inch group. Subsequent loads,(several thousand), all shoot to 1 inch or sometimes a little less. I figure that's all the factory stock bushmaster barrel is capable of.
Subsequent loadings of 69 gr. Nosler J-4 match HP, have produced a few sub-inch groups as small as .575. But not on a consistant basis.
The rifle has been modified from it's factory configuration, full floating fore-end, DPMS gas block, and a jewel trigger.
The point I'm trying to make is IF you want to get the most accuracy your rifle has to offer you MUST reload.