I would and do use magnums for any cartridge using W296/H110. Not to say regular primers won't work; they likely will but may not be 100% reliable especially in very cold weather. Not really a safety issue except that if you do experience a misfire, don't fire another without checking the barrel for a possible stuck bullet (as always). If you can get magnums, it isn't worth the risk to use something else IMO. And yes, either way a good firm crimp as Troy mentions.