i agree buy new ones
still there is the heat option

yes they do become welded but the heat causes a reaction and they seperate but like i pointed out saftey side of things i dont know wat it would do wen you heatit do it slowly and carefully as not to burn the pipe but it will become very soft its good for saving fittings but not the best for keeping...

my first post guys
to seperete them you can use a heat gun and gently heat around the join and twist once the glue has released keep twisting
i have done this many times
but i have never done it for a cannon so the saftey side of things i dont know
hope that helps