I just bought used a great (it looks like) AR15 with the above mentioned barrel specs, but since I haven't been able to ID the barrel yet, I don't know if it's got a Match chamber or not (and I don't know if it'll matter, depending on the ammo I end up getting).  I have been learning as much as I can about ROT and bullet weights and accuracy and fragmentation.  I've read  until my eyes cramped up, but have come up against the problem:  

1.  I need a round that I can actually afford to buy some quantity (1000 rounds plus) of, on a less than gourmet budget.  The GPSS deal I read about through here is great and looks like great ammo, but I only spent a little more than their advertised cost for a case of ammo on my friggin gun!

2.  It needs to at least not fly apart coming out of a 1:7 ROT barrel, with enough length to put some real stank on a round.  Ergo, I think, no varmint ammo, but 55 grain makes me leery too.

3.  It needs to be accurate (to make my sorry ass happy, anyway) out to 500 yards.  I have no idea what accurate of my rifle will be, so maybe just consistency will suffice.

4.  It needs to be a round that doesn't take a presidential order to be able to find.  I want to be able to order more of the stuff as I shoot through it.  All things being equal, I'd like to go through a thousand rounds every three weeks or so, and be able to find more, since I can't go shelling out huge quantities of money all at once (see above my whining about GPSS's ammo).

I just can't seem to put it together.  Any suggestions would be most helpful.

Uriel

Get into reloading, look for the equipment at gunshows online etc, once you have the equip you can try various loads untill you find the one your rifle and wallet likes. Or see if anyone in your area has a press that they will teach you on.  If you ever go to the PRK I would do it, When you get several people together and go in on bulk purchases the cost will go down as well.  Good Luck