As stated above, for longer than 300 yards, you will be better off with the 68 grain bullets and heavier, using a 1:8 to 1:7 twist barrels.  Most high masters I know use a 1:8 twist and Sierra 80 grain bullets for 600 yards.  I would not use a 16" barrel.  Once again, as stated above, you will want all the velocity you can get.  Look for a barrel maker who shows you targets representing how a barrel will be expected to group at various distances.  Look for true match chambering with a specifically matched bolt to the barrel, when it was made, not at a later time.  Minimum chambers help make a tight shooting barrel.  Accuracy rests on the three "B"s: barrel, bullet, and brass, in that order.  The heart of an accurate rifle is the barrel.  Expect to spend $350, usually more, for a top tier target barrel, using a Lothar Walther, Douglas Premium, Krieger, Lilja, Broughton, Pac-Nor, or other high quality barrel maker.  Other good barrels can be found in the $250 range, but it has been my experience that about half of these would not hold MOA with quality, match ammunition.  If you are happy with a barrel that may shoot upwards of 2 MOA, then a lower priced barrel will work fine.  To keep this in perspective, 2 MOA is a 12.56 inch group at 600 yards, in a perfect world, and that does not include wind, thermals, bullet variation, velocity variation, and shooter inputs.

Yes.  The Sierra 77 grain bullet is designed for magazine length loaded ammo.

The only other AR platform I would consider is the AR-10 (.30 caliber) for long range use. This means a whole new rifle all together, and mags, and..... What is appealing about the AR-15 platform is that is is pretty common and components are almost still affordable.

They are also easy to find with little thought about "will this work?" It IS possible to get an accurate barrel at 600yards that will shoot heavy bullets (80  grains) and then use that same barrel/set-up to shoot lighter bullets at a shorter distance confidently.

Also resale for a .223 and its components (that are in good condition) is pretty likely.

(Edited to fix spelling.)

I want one too.

Quoted: I want one too.

You have a MAC-10. You can't have one!  


M4-Stag,

You are right. As soon as you are "done" with your build there is something else you just found out you needed. Damn You black rifle disease!!!