The Coonan DID get the function "bugs" worked out of cranking "Rimmed Revolver Ammo" through an autoloader.
If I remember correctly it did not take kindly to most handloaded .357 ammo. Once you found the factory load that it "liked" ~ then it was awesome & reliable.
Since there was no loss of oomph out of a revolver "cylinder gap" .357 Mag velocity was a bit higher in the Coonan.
The PROBLEM with buying a "Like New or Mint Condition" Coonan NOW is the general rarity of the Coonan magazines. Expect to pay BIG bucks for spare mags "if & when" they pop up.