I'd say first, make sure that the .223" bullets will fit the throats of your M-53 (if that's what you are shooting). If that isn't an issue, then I would have no quams about using them, but I would back down on my charges by at least 10% and work back up. A thou may not be a big difference in a .44 or .45, but it will be more noticable in the .222 bore of a Jet. Still, there are a lot of different .223 bullets available for the .218 Bee and .22 Hornet which are generally .224", but some of the early ones were .223" nominal groove diameter (thus the reasoning behind that diameter bullet), and I haven't heard of anyone blowing one of them up by using .224" bullets in them.