what ammo should i use to break in and zero my rra chrome lined 1 in 9 twist rate barrel?  would there be a difference if my twist rate were 1 in 7?  thanks.

I know of none.

There's plenty of posts here about barrel break-in. Most will say just "shoot the darn thing", if it's a chrome lined barrel.

I've always used SAMMI spec factory loaded ammo ... 55gr FMJ in my 1/7 twist.

And I really like the 62gr as well.

Quoted: To break it in, JUST SHOOT IT. To sight it in, use whatever you're gonna shoot the most.

+1 (i wouldnt use WOLF for break-in, or any time, )

But... would it be theoretically better to break in the rifle using full load XM193 or lighter loaded Federal .223?

Run a case of XM193 through it

ellery, that is closer to what i'm asking.  does breaking in a new barrel matter w/hotter loads?  as far as zeroing, if i'm only shooting w/in 200 yards or so, will match grade ammo make much of a difference between that and the winchester q3131a?  thanks for the replies too.

It doesn't matter just shoot the shit out of it.

Insert magazine full of your choice of ammunition (mine is XM193/Q3131A)
Shoot until empty.
Eject empty magazine.
Repeat, until you run out of ammunition or get tired.  Just have fun.

alright, i think i understand now hink   thanks

Try some Mk 12 SOPMOD stroke bravo niner 99 grain tard ammo!

Quoted: Run a case of XM193 through it

+1

Quoted: But... would it be theoretically better to break in the rifle using full load XM193 or lighter loaded Federal .223?

You're overthinking the problem - just shoot it - either ammo is fine.

THIS IS MY RIFLE. There are many like it but this one is mine. My rifle is my best friend. It is my life. I must master it as I master my life. My rifle, without me is useless. Without my rifle, I am useless. I must fire my rifle true. I must shoot straighter than any enemy who is trying to kill me. I must shoot him before he shoots me. I will....

My rifle and myself know that what counts in this war is not the rounds we fire, the noise of our burst, nor the smoke we make. We know that it is the hits that count. We will hit...

My rifle is human, even as I, because it is my life. Thus, I will learn it as a brother. I will learn its weakness, its strength, its parts, its accessories, its sights and its barrel. I will keep my rifle clean and ready, even as I am clean and ready. We will become part of each other. We will...

Before God I swear this creed. My rifle and myself are the defenders of my country. We are the masters of our enemy. We are the saviors of my life. So be it, until victory is America's and there is no enemy, but Peace.

Just remember you can get more accurate with your rifle by shooting it more, than you will worrying

about the loss of accuracy from  some lengthy break in procedure.

Shoot it and the shoot it some more.  I doubt you will ever wear it out.