I beleive Kreiger says that it is safe, but I'm not sure, I would use Hoppes #9 BR or something similar that disolves copper rather than wears it down. I used Bore Bright to help reduce pitting due to Rust, seemed to help.
I have used Isso boren paste it works.I also have used JB's bore paste for years without any problems,really gets the carbon buildup and moly out.After that I use Sweets7.62 to check for any remaining copper.
I have always used JB's to break in a barrel on a new factory gun. Didn't need to on a custom barrel though. /ubbthreads/images/graemlins/smile.gif
I usually use about 50 strokes with a patch with JB's smeared on it changing patches and more borepast every 10 strokes and only comming in from the breech end and pulling off the patch when it comes just comes out the muzzle. I also use a brass cleaning jag and only come out enough to get the patch off and never drag the steel rod over the muzzle.
I look at it like this, its no differant than shoot one clean it shoot one clean it until the barrel smooth's up like a lot of people do for break in. I'm just doing the same thing without the shooting.
I have found that about stroke 20-25 things begin to work a lot easier. Sometimes with a tight patch the first 20 can be tough to do but when it smooths up its like walla. /ubbthreads/images/graemlins/cool.gif
It can make a gun that shoots loose groups right off the bat turn into tight groups from the getgo on a factory gun.
But to each his own, its just something I learned over 25 years ago and have kept it up on all my new factory guns. Similar to hand lapping the barrel.