No issues with two or more barrels fitted to the same frame, I had two 357 barrels fitted to mine recently, then sent one barrel to another member.
Actually an extractor is an easier conversion since there's no lift button to worry about, just change the extractor claw to a 30-06 which can be ordered from H&R, see the Handi owner's manual download at H&R or in the FAQs for the extractor part number. I just converted my ejector 35Rem to a spring assisted extractor, it's an improvement over a factory extractor, see the FAQs.

Tim