I am ordering a new rifle for CMP, and possible IPSC 3gun use(RRA NM A2). Any thought on brand and model of factory ammo for either purpose?

Don't won't to start an ammo brand war, just looking for some guidance....

Are these rifles like competiton small bore rifles, where you need to run a few different brands through to see what works/groups best?

Anything regarding ammo and barrel/gun break in? How many rounds until it is "broken-in?"

Thanks in advance!

I shoot IDPA matches, and some of the matches are 3 gun matches. I have not shot any CMP matches yet. My best guess for CMP would be  ammunition manufactured by Black Hills. For three gun I have used winchester white box and Q3131a. I have also seen some folks use XM193 for the 3 gun. Your rifle will need to have a 5.56 chamber to use Q3131a and XM193 or Nato  pressure ammunition. If your rifle has a match chamber( I believe the rifle you have chosen does have a match chamber)  I woud avoid these two choices and try standard pressure, or match ammunition by Black hills or Winchester. You will definitely have to experiment with different types of ammunition for both disciplines to find what will work best for you and your rifle.
As for barrel break in I believe you will find a definitive instruction on the ARMALITE website or the BERGER bullets website. I haven't done it in so long that all I can remember is that for the first 10 shots you clean after each shot with a patch and standard solvent. Then the next 10 you clean after every second shot and so on, but I am not exactly sure except it is a PTA and has to be a labor of love.

No other responses on this?

C'mon guys, I need your experience on this!

I use 77 SMK's.  I handload mine, but Black Hills is supposed to be making it.

If you have a 1/9 twist, use the 69gr Black Hills match for the CMP.  77gr would do better with a 1/7 twist.  For the IPSC/IDPA stuff any 55gr will give serviceable accuracy.  Using match in those cases would be overkill.  If you do have the .223 chamber, stick with the standard commercial stuff.

I have found that Winchester 40 rd Value pack for $7.59 at Wally World would great.  It's .223, 55 gr.  The last few boxes said it was made in Israel just like the Q3131A is.  It  probably doesn't have the same velosity but it cycles my AR's and doesn't have a much recoil.  Been using it for two years.

If you're going to be compeditave in NRA HP and the CMP service rifle classes, you need at least a 1\8 twist barrel. Reason being that at 600 yards, you are going to want to shoot the 75\77\80 gr rounds, and not all 1\9 barrels will group these heavier bullets. You may get luckey with a 1\9, but if you don't you will be limiting yourself to the 69 gr round for the 600 yard line. The current best deal in ammo for my money is "The Major' in NJ.

http://www.radomski.us/njhp/major.htm

I've used this stuff at 600 yards, and if I do my part it's all in the 10 ring. Black Hills is the only other factory match ammo I've tried, and every weight shot the same group at 200 yards. AR's are pretty ammo tollerant and usually shoot almost everything well. I will continue to buy the Hornady factory reloads for everything except the 600 yard line, which I'm going to start handloading for this winter.

Echo Sgt. Gold's comments.

For CMP/NRA matches, you CAN use 55gr stuff for 200 and 300, but not at 600 competitively. My experience with 55gr FMJs (XM193, Q3131A, American Eagle) is that it will hold the 10-ring on the 200 yard target (7-inches or so), but I don't trust it to do better then the 9-ring at 300 (about 13 inches, give or take) .  This is from position in my rifle. Using a bench and/or a different rifle may change these results.

Of course, I reload match ammo. Try Black Hills loaded with the 77gr HPBT (I don't know if they use Noslers or Sierras, but I am assuming Sierras). These will work reasonably at 600, but if you live in a windy area I'd suggest learning to reload and using 80s for the long line.

Anyway, good luck and good shooting. (And if you do alot I suspect you will find the National Match AR is a little porky in IDPA/IPSC-type shooting, especially if you decide to weigh yours like most people do.)