I saw and was tempted to buy a M1 carbine. The price was 350$ but I did not get it because the caliber was 256 ferret.

What the heck is a 256 ferret? I never heard of it.

Now I could have gotten the rifle and had it rebarreled I guess.

Just interested in info on the unusual wildcat.

I cannot find anything online really. Looks to be a necked down 30 carbine.

A quick google  search for ".256 ferret m1 carbine" revealed a few links of interest

-Universal factory bolt

-Universal NIB 256 Ferret

-From Wapahani "256 Winchester Magnum (Universal Model 1256 Ferret):  Introduced in the late 1970's, the 256 Winchester Magnum round was an attempt to increase the stopping power of the weapon.  It was only popular for a few years before being phased out of production in the mid 80's."

-A post here on American Backyard Forums

Even more information available if you feel like poking around online

Edited to correct link.