OK one last question for now. I am looking at building a pre-ban tactical carbine with a bushmaster 16" barrel fluted ( shorty or a v match) what range are 16" barrels good for, what about groupings?

Spanky - My friend and I have 24" bushy varminters and have been working on loads to date.  His does 1/4" to 3/8" at 100 yds pretty regular. Not mine yet:(

However, there was a guy named Neil with a bushy V Match at the range - That rascal was shooting 1" groups at 100 regularly with no cleaning between groups - not to be sneezed at for a chrome lined barrel....

It depends on ammo and what you're using for sights, but I've been able to place mag after mag into coffee mug sized groups at 225 yards. Any farther than that and the wind starts to play with you.

Best group was 10 shots into 3". Groups expand to the size of paper plates after fatigue sets in... not the rifle's fault. :o)

Ammo was Winchester Q3131a, barrel was a 16" Colt 1/7 M4 barrel, and a Leupold VariX-III 2.5-8x36 for optics.