I bought one back in the mid nineties new from beech grove firearms and maybe put 500 rounds through it. It was very perticular to ammo and jammed a lot.i don't remember what it was but kind of like any 1911 they shoot best with hardballs. I would not buy hollow points that were dished out real bad.Good thing is that there is a lot more ammo choices now than what I had ten years ago.
I know Coonan does not make a specific mag for the oider models but perhaps they can help you with your mag problem. I know they sell used for big bucks on Gunbroker. Check their web site and shoot them an email with your question; they are great folks to work with.
I had a coonan late 80s or so loved it,reloaded every thing I shot then.I think it was 158gr swc and win 231 dont rember a problem and wish I had it back.