Yes it can be safe if done safely and properly. It is being done now on a more frequent basis. That said, before you try it do a little research here and ask for help if unsure of ANYTHING. Only fit barrels to actions that have been manufactured for the appropriate pressure levels. This was a kind of a shadowy back-room type of going on until H&R added the extra fee and has since expanded greatly...go slow, ask questions and be safe....<><.... :grin:
The best way to go would be to buy the barrel from H&R and have them fit it for you. That way they will stand behind any problems that might arise of the barrel and barrel fitting.... :grin: