The reg should come with a burst disc already fitted.
DO NOT EVER EVER PUT LOCTITE ON THE THREADS! COME TESTING TIME YOU'LL BE BUYING NEW BOTTLE AND REG!!!!
With 4500psi behind the bottle it will not come undone. I had a pre-set that some muppet had loctited and managed to get it off without destroying anything. A team mate wasn't so lucky and had to buy a new reg and bottle as H-PAC were unable to get them apart for testing without wrecking the threads.
i would not use lock tight but out of hundreds of bottles ive had tested with lock tight only one has failed, and that was not due to lock tight just they did not want to test it as it had been used for co2.