Lee liquid alox is what I use as a release agent bedding rifles.
I should not think it has any adverse effects on metal,in fact it should act as a good rust preventative.
I always take them out first however to tidy up the job and remove any plasticine I may have used to stop the epoxy going where I did not want it to go.
Good idea shooting it first to loosen it up,I will try that next time ones a little "tight".

GDU