I have a pardner 20 gauge and a handi-rifle in .223. Is it possible to buy a .243 barrel for one of them? I have a son that is ready to start hunting deer, and this would be a great way to get him into it on the cheap.
H&R/NEF basically makes (2) different types of receivers. The SB1, which is weaker model used for shotguns, muzzleloaders, and some lower pressure centerfire cartridges. And the SB2, which can handle all of the above.
You can have H&R fit a .243 barrel to your .223 Handi. You will have to send in the receiver for them to fit it. It is also recommended by H&R that you send in the stocks as well.
Or, you can buy a .243 barrel privately and hope it fits. If it doesn't fit you may have to either file the pivot point on the barrel lug or shim it.
H&R/NEF barrels aren't directly interchangeable like T/C Contender barrels are. They need fitted to a specific receiver.