your best bet, and the easiest to convert are the e. german mags, with the big steel rib down the back.
http://www.fbmginc.com/ or
http://www.classicarms.us/
the saigas are fantastic. I have one of each in the 16 in bbls. the are all chrome lined , cold pour,hammer forged, bbls. the 223 that i have is moa at 100 yds. the others are quite acc as well, so much so that i do not scope them.
One time at the range, I put up 3 inch shoot and see targets. i put 100 rounds of mostly black hills , winny 45 varmints, and other brands, into my mags.
i then shot every shot within 5 secs of each other, as fast as i could get back on target and breathe , basically. with diff brands, i Hit one, 3 inch shoot and see, 96 out of 100 times. Awesome! this was without a scope as well.
I have never had the longer bbl versions , so I am unwilling to say how accurate they are, but I have never heard any complaints.