what needed to convert model 12 .223 to a .243??

i assume a barrel change and bolt face? what about the internal magazine? thanks

Beside's the barrel and bolthead, you'll need to change the mag box & follower.
You'll also need to change the front bolt baffle. Yours should have the dogleg on it to shorten the bolt throw.

bolt baffle? i assume this isn't too expensive or hard to do? thanks

Not expensive or too difficult. Changing the baffle is easy since you will have to change the bolt head anyway. Midway has them as well as brownells and I am sure you can get one from SSS as well.

I believe you also need to replace the extractor.

Nah, the extractor is the same.

However, some of the pre-AccuTrigger rifles have an extractor made with beryllium (they are sort of copper colored) that have given some people extraction problems (I never had any though) so a change to one of the new steel extractors might not be a bad idea if you happen to have the old style.

thanks for the replies, it helps out in a possible decision.