I am completely new to these H&R single shot rifles,know nothing about them.Yesterday I came across a H&R classic carbine in 45 colt.That caliber is my favorite so I purchased it.While at another shop the dealer mentioned that he had a 223 H&R bbl for 50 bucks so I jumped on it.I took the 45 bbl off the receiver and put the 223 on.It was a perfect fit,opens and closes perfect.Is this normal or do I have to have a smith do some fitting to make it safe.I'm a little afraid to shoot the 223 right now because I don't know enough about these guns.Where can I learn about which bbl can go on what frame etc.