A buddy of mine at work is looking for a good coyote rifle, most likely a .223 or 22-250. He just found out through his dad that his uncle has a rifle that is a .257 necked down to a .22. I've never heard of it, I'm assuming that it is a 257 Roberts, though I'm not sure. I was looking for any information on this cartridge. Thanks.

It is called 5,6*57rws factory loaded or 224 TTH the same reinvented. Search the forum!

Kimmo

Watch the various cartridge dimensions, particularly the neck wall thicknesses. The 5.6 X 57mm RWS cartridge has thick neck walls to allow for using cartridge adapters to use .22 WMR and .22 LR. Using 5.6 X 57 mm RWS cartridges in a .22-.257 could be disastrously unsafe, depending on the exact chamber dimensions.

The general point to be taken away from this is that when factories adopt "wildcat" cartridges, there is a risk that the factory loaded ammunition or brass may not be safe in all of the preexisting "wildcat" rifles. Factories tend to have a preference for thicker neck walls than wildcatters, so using "factory" ammunition in a wildcat rifle is an endeavor to be approached with caution. A look at the reamer drawing or a chamber cast or a check of the ammunition that has been modified for use in the rifle can be helpful.

That's not precisely the matter that is being considered in this case. There are a lot of versions of .22 X 57mm and they are not all interchangeable.